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Brucellosis as a cause of acute febrile illness in Egypt
Transactions of the Royal Society of Tropical Medicine and Hygiene (2007) 101, 707—713
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Brucellosis as a cause of acute febrile illness in Egypt Gregory J. Jennings a, Rana A. Hajjeh a,d, Fouad Y. Girgis a, Moustafa A. Fadeel a, Mohamed A. Maksoud a, Momtaz O. Wasfy a, Nasr El Sayed b, Padmini Srikantiah c,d, Stephen P. Luby d, Kenneth Earhart a, Francis J. Mahoney a,d,e,∗ a
US Naval Medical Research Unit-3 (NAMRU-3), Cairo, Egypt Egyptian Ministry of Health and Population, Cairo, Egypt c San Francisco General Hospital, San Francisco, CA, USA d Centers for Disease Control and Prevention, Atlanta, GA, USA e Eastern Mediterranean Regional Office, WHO, Cairo, Egypt b
Received 12 July 2006; received in revised form 26 February 2007; accepted 26 February 2007 Available online 17 April 2007
KEYWORDS Brucellosis; Brucella melitensis; Brucella abortus; Surveillance; Incidence; Egypt
Summary To develop better estimates of brucellosis incidence, we conducted populationbased surveillance for acute febrile illness (AFI) in Fayoum governorate (population 2 347 249), Egypt during two summer periods (2002 and 2003). All hospitals and a representative sample of community healthcare providers were included. AFI patients without obvious etiology were tested for brucellosis by culture and serology. Incidence estimates were calculated adjusting for sampling methodology and study period. Of 4490 AFI patients enrolled, 321 (7%) met the brucellosis case definition. The estimated annual incidence of brucellosis per 100 000 population was 64 and 70 in 2002 and 2003, respectively. The median age of brucellosis patients was 26 years and 70% were male; 53% were initially diagnosed as typhoid fever. Close contact with animals and consumption of unpasteurized milk products were associated with brucellosis. The high incidence of brucellosis in Fayoum highlights its public health importance, and the need to implement prevention strategies in humans and animals. © 2007 Royal Society of Tropical Medicine and Hygiene. Published by Elsevier Ltd. All rights reserved.
1. Introduction ∗ Corresponding author. Present address: NAMRU-3, PSC 452 Box 5000 (code 304), FPO AE 09835, Egypt. Tel.: +11 202 276 5287; fax: +11 202 276 5414. E-mail address: [email protected] (F.J. Mahoney).
Brucellosis is a zoonotic disease that is widely distributed throughout the developing world. In 1992, WHO reported that 86 (49%) out of 175 countries were affected, with an estimated population at risk of 2.4 billion persons (WHO,
0035-9203/$ — see front matter © 2007 Royal Society of Tropical Medicine and Hygiene. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.trstmh.2007.02.027
708 1996). Surveillance data suggest that brucellosis incidence is increasing in many countries of the Mediterranean Region and the Middle East (WHO, 1997). However, it is not clear whether the increase reflects improved surveillance and better recognition of disease or a true increase in disease incidence. Estimates of brucellosis incidence in Egypt are based primarily on surveillance data reported from infectious disease hospitals (n = 108) throughout the country. Data from these hospitals indicate considerable variations in disease incidence by region, with rates ranging from 0.2 to 26/100 000 (data from National Information Center for Health and Population). The diagnosis of brucellosis in this surveillance system is based almost entirely on clinical criteria with little laboratory confirmation of disease. Laboratory-based surveillance among patients with acute febrile illness (AFI) admitted to infectious disease hospitals throughout Egypt reported that 11% of patients had evidence of acute brucellosis (Afifi et al., 2005). While these data indicate that brucellosis is widespread in Egypt, there is little reliable information on disease incidence. To better characterize the epidemiology of dis-
G.J. Jennings et al. ease and better define disease burden, population-based surveillance for patients with AFI was established in Fayoum Governorate (population 2.3 million). This paper summarizes the results of surveillance activities over a 2 year period and discusses the implications of these studies for public health control measures.
2. Materials and methods Fayoum Governorate, located ∼100 km southwest of Cairo (Figure 1), is geographically isolated by desert, which limits population mobility, making it a suitable site for population-based surveillance. The governorate is divided into six administrative districts and is largely agrarian, with a total estimated population of 2 347 249. Population-based surveillance for patients with AFI was conducted in two time periods, including June to October 2002 and June to October 2003. Case-finding methods involved recruitment of a representative sample of primary care providers from all tiers of health service in the study area. These tiers included the infectious disease hospital, all six district general hospitals, all infectious disease or ‘fever’ specialists and a random sample of rural health units and primary care providers. We defined primary care providers as general practitioners, internal medicine physicians or pediatricians. In 2002, approximately 10% of rural health units (13/138) and primary care providers (18/186) participated in the surveillance. All providers were randomly selected from a comprehensive roster of practicing physicians in the catchment area. Provider enrollment was expanded to 20% in 2003, to obtain better estimates of disease incidence at the district level. None of the selected primary care providers refused to participate in this study.
2.1. Case definitions AFI was defined as any individual ≥1 year of age with a temperature greater than 38 ◦ C at the time of visit, or history of fever of more than 2 d duration, and no identified cause of fever such as diarrhea, hepatitis and respiratory tract infections, or alternatively any patient with a clinical diagnosis of typhoid fever or brucellosis. A case of brucellosis was defined as an AFI patient with laboratory-confirmed brucellosis, established by the isolation of Brucella spp. from blood culture or a serologic titer ≥1:320 by the tube agglutination test.
2.2. Data collection
Figure 1 (A) Location of Fayoum Governorate, ∼100 km southwest of Cairo, Egypt. (B) Brucellosis incidence for 2003 for Fayoum Governorate and its six administrative districts.
All patients meeting the case definition of AFI were invited to participate in the study. Providers were trained to conduct a standardized clinical and laboratory evaluation, including collection of blood cultures and serum samples at the time of clinical evaluation. Data from consenting patients were collected using a brief, standardized questionnaire that included information on demographic and clinical characteristics. In 2003, questions were added to the questionnaire regarding antibiotic use, occupation and animal exposures.
Brucellosis as a cause of acute febrile illness in Egypt
2.3. Incidence calculations We calculated the incidence of brucellosis after considering the provider-sampling scheme, diagnostic test sensitivity and specificity and duration of sampling (Crump et al., 2003). To account for provider sampling, we derived a representative arithmetic multiplier for each of the five tiers of healthcare providers. In 2002, 89% of fever specialists were enrolled for a multiplier of 1.1. In 2003, 93% of fever specialists were enrolled for a multiplier of 1.1. In 2002, 9.4% of rural health units and 9.7% of primary care providers were enrolled for multipliers of 10.6 and 10.3, respectively. In 2003, 19.4% of rural health units participated for a multiplier of 5.2, and 18.5% of primary care providers were enrolled for a multiplier of 5.4. Because the majority of brucellosis cases can be detected with a combination of blood culture and serology, we assumed that test sensitivity approached 100%; consequently we used a multiplier of one. To adjust the 20 week study period to represent an entire year, we multiplied the number of patients with brucellosis identified during surveillance by 2.6 (Table 1) using estimates of seasonality based on the monthly distribution of hospitalized patients with brucellosis in Egypt from 1999 to 2003 (Afifi et al., 2005).
2.4. Statistical analysis Data were double-entered into a Microsoft Access database. Population incidence was calculated using annualized census estimates. To characterize risk factors for disease, we compared brucellosis patients with other AFI patients who were culture negative for typhoid fever. Basic descriptive analysis of demographic data and age-adjusted prevalence ratios were calculated using Epi Info 2000 (CDC, Atlanta, GA, USA). A P-value <0.05 was considered statistically significant.
2.5. Clinical and laboratory methods Healthcare providers were supplied with materials for venipuncture and blood culture and trained in sterile collection techniques. The patients’ blood was inoculated into a biphasic blood culture bottle (bioMerieux, Marcy l’Etoile, France) by the attending physician. Serum samples were processed on the day of collection and testing was performed at the Fayoum Infectious Disease Hospital or Fayoum Governorate General Common Laboratory. Standard tube
Table 1
709 agglutination (STA) was performed following the manufacturer’s instructions (SA Scientific Inc., San Antonio, TX, USA) using antigen for B. abortus (strain USDA #1119-3). Agglutination titers of ≥1:320 were considered positive (Young, 1995). Blood culture bottles were incubated at 37 ◦ C for 5 d and observed daily for signs of bacterial growth in either the liquid or solid phase. An aliquot from any blood culture bottle with suspected growth was transferred to blood, chocolate and MacConkey Agar for bacterial isolation and characterization. All blood culture bottles were transferred to a referral laboratory at NAMRU-3 after 5 d incubation, and maintained at 37 ◦ C for an additional 21 d in order to monitor for growth of Brucella spp. Speciation of Brucella isolates was conducted using PCR primers and conditions developed by Bricker and Halling (1994). As a performance indicator, contamination rates of blood cultures were monitored and additional training provided when necessary. All cultured bacteria and serology results obtained at laboratories in Fayoum Governorate were confirmed at NAMRU-3.
3. Results In total, 4490 patients with AFI were evaluated in 2002 and 2003, and of these 321 (7.2%) met the case definition for brucellosis. In 2002, 135 patients had laboratory-confirmed brucellosis, with an estimated incidence of 64/100 000, while in 2003, 186 patients had laboratory-confirmed disease, with an estimated incidence of 70/100 000 (Table 1). In 2003, brucellosis incidence rates varied widely between districts, and ranged from 38/100 000 in El-Fayoum to 181/100 000 in Tamiya (Figure 1). Of the 321 patients with laboratory-confirmed brucellosis, 115 (36%) were diagnosed by culture and 206 (64%) were diagnosed by serology only. Other pathogens isolated included Salmonella typhi (n = 264), Staphylococcus aureus (n = 10), Escherichia coli (n = 6), other Salmonella species (n = 3), Enterobacter species (n = 2) and Streptococcus pneumonia (1). Among patients with culture-confirmed S. typhi infection, only 2 (0.8%) had Brucella tube agglutination titers ≥1:320. Among the 115 patients with cultureconfirmed brucellosis, 15 (13%) had titers below the cutoff (1:320). The overall contamination rate (mainly skin flora) decreased from 18.0% (320) in 2002 to 9% (239) in 2003. The species of 114 Fayoum Brucella isolates characterized
Brucellosis incidence estimates for Fayoum Governorate in 2002 and 2003, showing five tiers of healthcare providersa
Year Healthcare provider
2002 2003 a
Test sensitivity multiplier
Fever hospital
District hospital
Rural Fever Primary care Total health unit specialist provider
21(21) 11(11)
17 (17) 19 (19)
18 (187) 28 (144)
52 (58) 55 (59)
27 (279) 73 (395)
135 (562) 1 186 (628) 1
Time frame
Total cases
Incidence/ 100 000
2.6 2.6
1772 1897
64 70
The number of patients identified by healthcare providers at each sampling tier are multiplied by the provider multiplier (total no. providers/no. providers enrolled) to yield the adjusted number of cases (in brackets). Because the vast majority of brucellosis cases can be detected with the combination of blood culture and the tube agglutination assay, we did not apply a multiplier to account for test sensitivity. A time frame multiplier of 2.6 was used for the 20-week study period based on seasonality of disease and the reporting period. The total number of adjusted cases was divided by the population to yield the incidence.
710
G.J. Jennings et al.
by PCR identified 113 (99%) as B. melitensis and a single B. abortus.
soft cheeses or yogurt) was also associated with increased risk.
3.1. Demographic characteristics and exposures
3.2. Clinical characteristics
The majority of brucellosis patients were male (70%) with a median age (25 years) that was significantly higher than the age of patients with S. typhi infection. There were no significant differences in the age and gender distribution of patients with culture-confirmed disease when compared to patients confirmed by serology alone (Table 2). Disease incidence among children 0—9 years of age was sevenfold lower than other age groups (Table 3). Patients with brucellosis reported a variety of exposures commonly associated with Brucella infections (Table 4), including close contact with buffalo, cattle and sheep. In addition, brucellosis patients were more likely to be farmers or involved in animal husbandry. Consumption of unpasteurized dairy products (e.g.
The distribution of clinical signs and symptoms was similar among patients with culture- and serologically-confirmed disease. The most common presenting signs and symptoms included history of fever greater than 2 d duration (99%), headache (86%), fever at time of presentation (82%), arthralgia (75%), undulating fever (58%) and abdominal pain (57%). Generally, the clinical features of brucellosis patients were similar to those of other AFI patients (including typhoid), except for undulating fever and arthralgias, which occurred with significantly greater frequency among brucellosis patients (P < 0.05). In addition, patients with brucellosis tended to wait longer than other AFI patients before seeking medical care (median time of 7 vs. 4 d). Brucellosis
Table 2 Selected demographic and clinical characteristics of brucellosis patients, population-based surveillance, Fayoum Governorate, Egypt, 2002—2003 Characteristic
Laboratory-based diagnosis Culture-confirmed brucellosis (n = 115)
Median (range) age (years) Males (%) Median days fever before medical care Mean duration of fever Headache (%) Abdominal pain (%) Undulant fever (%) Arthralgia (%)a Rash (%) Nausea (%) Vomiting (%) No. (%) treated with antibiotics No. (%) treated with more than one antibiotic
Culture-negative AFI (n = 3524)
Brucellosis confirmed by serology (n = 206)
Culture-confirmed typhoid (n = 264)
25.5 (3—70) 142 (69) 6
11 (2—54) 146 (55) 5
20 (1—100) 2144 (61) 4
11.4 101 (88) 69 (60) 66 (57) 54 (75) 6 (5) 46 (40) 31 (27) 73 (64)
10.2 176 (85) 113 (55) 120 (58) 85 (75) 16 (8) 88 (46) 75 (36) 142 (69)
7.5 215 (81) 182 (70) 111 (42) 94 (57) 12 (5) 106 (40) 108 (41) 175 (66)
6.2 3037 (86) 2426 (69) 1445 (41) 1472 (70) 0 1605 (46) 1332 (38) 2333 (66)
68 (59)
128 (62)
171 (65)
1861 (53)
22 (1—62) 81 (70) 6
AFI: acute febrile illness. a Data on arthralgia were not collected in 2002.
Table 3
Annual incidence rates of brucellosis by age group, Fayoum 2003a
Age group (years) 0—9 10—19 20—39 ≥40 Total a
No. cases 8 61 69 48 186
Adjusted no. cases
Population
Incidence/100 000 year
29.6 205 231 163
674 112 618 315 620 392 434 430
11 86 97 97
629
2 347 249
70
Patients identified by healthcare providers at each sampling tier were stratified into four age groups and multiplied by the provider multiplier (total no. providers/no. providers enrolled) to determine the adjusted number of cases. Incidence was calculated by dividing the number of adjusted cases by the estimated age-specific population for each age group (population data provided by the National Information Center for Health and Population).
Brucellosis as a cause of acute febrile illness in Egypt
711
Table 4 Comparison of various relevant exposures between patients with brucellosis and patients with other acute febrile illnesses; univariate analysis, population-based surveillance, Fayoum Governorate, Egypt, 2003 Exposure Cattle Farm work Buffalo Contact with an aborted animal fetus Soft cheese or yogurt Slaughter Sheep Raw milk a b
No. (%) cases exposed (n = 186)a
No. (%) non-brucellosis patients exposed (n = 2320)a
Age-adjusted prevalence ratio
95% CLb
65 (35) 64 (34) 70 (38) 36 (20)
540 (23) 402 (17) 479 (21) 218 (9)
2.1 2.0 2.0 2.0
1.2—2.1 1.5—2.6 1.5—2.6 1.4—2.8
160 (86) 42 (23) 41 (22) 92 (50)
1796 (78) 327 (14) 333 (14) 984 (43)
1.6 1.5 1.5 1.3
1.1—2.4 1.1—2.1 1.0—2.0 0.96—1.7
Analysis was done for patients evaluated in 2003 only. 95% confidence limit; P < 0.05.
was the initial clinical diagnosis for 30% of patients with laboratory-confirmed disease, while 53% of these patients were initially misdiagnosed as having typhoid fever. The most common clinical diagnosis was fever of unknown origin (19%). The majority of brucellosis patients (83%) were managed in the outpatient setting; only 6% were detected at the infectious disease hospital. The use of antibiotics to treat brucellosis patients increased from 79 (58%) in 2002 to 133 (71%) in 2003. Among 271 patients with an initial diagnosis of brucellosis, the most commonly prescribed antibiotics were trimethoprim—sulfamethoxazole (22%) followed by chloramphenicol (19%), ciprofloxacin (15%), aminoglycosides (9%) and ampicillin (8%). In 2003, doxycycline, rifampicin and streptomycin were added to the list of antibiotics prescribed on the surveillance form. Physicians did not report prescribing any of these drugs in 2003. Only 24% of brucellosis patients received more than one antibiotic for initial treatment of their infection. We observed no significant differences in antibiotic treatment among patients who received inpatient care as opposed to patients who were diagnosed in an outpatient setting (i.e. primary care physicians, rural health units or fever specialists).
4. Discussion This population-based surveillance study provides estimates on the incidence of brucellosis in a well defined population in Fayoum Governorate, thus highlighting the public health importance of this disease in Egypt. These data also revealed that brucellosis is not well recognized as a common cause of AFI, which has important implications for clinical management and public health control measures. The present study was designed to define the disease burden associated with brucellosis in a rural Egyptian governorate. Only 5.7% of brucellosis patients were identified by hospital-based surveillance. If these hospitalized patients were used to calculate disease incidence, the rate would be 3.8/100 000 using a case definition based on laboratory confirmation or 6.0/100 000 if the case definition
were based upon clinical presentation alone. In this study, the laboratory criteria used for the serologic diagnosis of brucellosis (tube agglutination titers ≥1:320) are more stringent than those recommended by WHO (titers >1:160, WHO/CDS/CSR/ISR/99.2), thus the incidence may actually under-represent overall burden of disease. Although this study focused on Fayoum Governorate, studies of AFI patients have found that brucellosis is a common cause of disease in all parts of Egypt. In a study of hospitalized patients with AFI in diverse regions of the country, 12 to 40% had laboratory-confirmed brucellosis (Afifi et al., 2005). These data also suggest that disease is prevalent in both urban and rural settings in all parts of the country. As brucellosis is usually transmitted through exposure to infected animals or consumption of contaminated products, these studies imply that Brucella infection in domestic animals is widespread in Egypt (Refai, 2002). The incidence rates observed in Fayoum Governorate are consistent with those reported throughout the Middle East, which range from 8/100 000 in the Gaza Strip (Awad, 1998; Memish, 2001) to 40/100 000 in Saudi Arabia (Memish, 2001), 46/100 000 in Jordan (Dajani et al., 1989) and 85/100 000 in Kuwait (Mousa et al., 1987). A recent population-based serosurvey in southern Saudi Arabia demonstrated serological evidence of past exposure to Brucella among 20% of the population, with more than 2% having evidence of active disease (Alballa, 1995). Although brucellosis is recognized as a common cause of AFI in various parts of Egypt, this study revealed that it is often misdiagnosed and mistreated. More than half of all brucellosis cases were misdiagnosed as typhoid, and only a quarter of them received treatment with more than one antibiotic. We could not assess duration of therapy in this study. However, well-established clinical guidelines for management of brucellosis require treatment with two antibiotics for a minimum of 6 weeks in order to minimize the risk of relapse (Hall, 1990; Solera et al., 1997). It is therefore important to educate physicians in Egypt about proper treatment of brucellosis, and to develop national treatment guidelines. Furthermore, it is important to improve laboratory capacities available to physicians in Egypt in order to better diagnose brucellosis, especially as
712 the clinical presentation of this disease is relatively nonspecific. In the current study, we found that the majority of brucellosis patients were adult males, with approximately one-third citing their principle occupation as farmer. Exposures associated with infection included close contact with sheep, cattle or buffalo, exposure to an animal abortus (aborted fetus) and consumption of dairy products such as soft cheeses and yogurt. As these dairy products are often unpasteurized and produced locally, they represent a plausible source of infection. Consumption of raw milk was not identified as a risk factor for disease. However, this exposure was quite common among other AFI patients as well, indicating that a much larger sample would be needed to demonstrate a significant association. The current study was not designed to evaluate the proportion of brucellosis attributable to food versus animal exposures, and it is difficult to evaluate the potential impact of different prevention strategies. Better risk factor studies are needed to assess attributable risk due to these different exposures. Despite this limitation, the high frequency of exposures associated with well-defined risk factors highlights the need for extensive efforts to educate the population regarding potential food- and animal husbandry-related exposures. In addition to the hazard it represents to human health, Brucella infection has a considerable economic impact on animal husbandry, including significant loss in agricultural productivity due to abortions, sterility, decreased milk production and costs associated with veterinary care (Roth et al., 2003). In addition, the disease can be an impediment to animal movement and exportation. To better define the economic impact of disease, quality data are needed on the prevalence of disease in livestock populations, and estimates of control costs to both producers and consumers. However, surveillance and control of brucellosis in Egypt and other countries in the Eastern Mediterranean Region are complex, due to the diversity of domestic animal species that are infected, different modes of transmission from animals to humans, and the challenges of disease control. Animal husbandry is the primary occupation for a large sector of the rural population in Egypt, where the livestock population includes 2.8 million cattle, 3.2 million buffalo, 3.7 million sheep, 2.9 million goats and 220 000 camels (Refai, 2002). Seroprevalence studies of domestic animals indicate that Brucella infection rates vary widely among different species and in different parts of the country (A. El-Taweel, unpublished data; A.M. Montasser, unpublished data) (Refai, 2002). Vaccination of livestock populations is a well-recognized and agreed-upon strategy for control of brucellosis. However, delivery strategies are challenging, particularly in the Middle East, with diversity of species distributed over wide geographic regions. In Egypt, animal husbandry practices include close contact among different species; thus control programs targeting one species are likely to have a limited impact. In this project, B. melitensis was, with a single exception, the only species isolated. Brucella melitensis is typically associated with sheep and goats; however, the species is being increasingly recognized as a source of infection for both cattle and buffalo (Corbel, 1997; Hamdy and Amin, 2002; Stevens et al., 1994). The predominance of B. meliten-
G.J. Jennings et al. sis as a cause of disease in humans suggests that it has adapted to cattle and buffalo in Egypt, as exposure to these animals and their dairy products has been recognized as a source of infection. This cross-species adaptation creates a challenge to vaccination strategies, because vaccines such as Rev1 were developed to combat B. melitensis infection in sheep and goats (Zygmunt et al., 1994), while RB51 and Strain 19 were developed to reduce infection by B. abortus in cattle (Stevens et al., 1995). The use and efficacy of these vaccines in alternate hosts requires additional investigation (Denes, 1997). Coupled with the uncertainty regarding vaccine effectiveness is the uncertainty of program effectiveness. Considerable resources and program experience are necessary to implement and sustain animal vaccination programs with substantial investment from both the public and private sector. Experience in many countries suggests that it can take decades to eradicate brucellosis with a combined strategy of vaccination followed by test and slaughter activities. To establish an economic framework for such an investment, it is recommended that veterinary and national health authorities work together to evaluate available data on disease burden and cost-effectiveness of control strategies. Given the challenges of implementing control programs in animals, it is recommended that national health authorities and veterinary services work together to ensure pasteurization of commercial dairy products, increase public awareness of brucellosis and minimize high-risk occupational and domestic exposures such as handling an abortus. In addition, efforts are needed to educate clinicians on recognition of disease, to establish laboratory capacity to confirm the diagnosis and to ensure availability of appropriate antibiotics for treatment. Disclaimer: The opinions and assertions contained herein are the private ones of the authors and are not to be construed as official or reflecting the views of the Navy Department, Department of Defense, the U.S. Government, or the Egyptian Ministry of Health and Population. Authors’ contributions: GJJ, RAH, KE and FJM conceptualized and designed the study; FYG, PS, NES and SPL carried out the clinical assessments; MAF, MAM and MOW carried out the immunoassays and microbiological examination; GJJ, RAH, KE, MOW and FJM drafted the manuscript. All authors read and approved the final manuscript. FJM is guarantor of the paper. Acknowledgements: We would like to acknowledge the Fayoum Governorate Health Directorate and the physicians and laboratory personnel at hospitals and clinics in Fayoum Governorate for their valuable contributions to this surveillance study. We would also like to recognize Mr Muhammad El Mofty and Mohammed Adel for their valuable assistance in managing the Fayoum data and Dr Guillermo Pimentel for assistance during manuscript preparation. Funding: Global Emerging Infections Surveillance System, United States Department of Defense, and the US Agency for International Development, work unit #847705.82000.25GB.E0018.
Brucellosis as a cause of acute febrile illness in Egypt Conflict of interest: None declared. Ethical approval: Institutional review boards of NAMRU-3 and the US Centers for Disease Control and Prevention.
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Brucellosis as a cause of acute febrile illness in Egypt Gregory J. Jennings a, Rana A. Hajjeh a,d, Fouad Y. Girgis a, Moustafa A. Fadeel a, Mohamed A. Maksoud a, Momtaz O. Wasfy a, Nasr El Sayed b, Padmini Srikantiah c,d, Stephen P. Luby d, Kenneth Earhart a, Francis J. Mahoney a,d,e,∗ a
US Naval Medical Research Unit-3 (NAMRU-3), Cairo, Egypt Egyptian Ministry of Health and Population, Cairo, Egypt c San Francisco General Hospital, San Francisco, CA, USA d Centers for Disease Control and Prevention, Atlanta, GA, USA e Eastern Mediterranean Regional Office, WHO, Cairo, Egypt b
Received 12 July 2006; received in revised form 26 February 2007; accepted 26 February 2007 Available online 17 April 2007
KEYWORDS Brucellosis; Brucella melitensis; Brucella abortus; Surveillance; Incidence; Egypt
Summary To develop better estimates of brucellosis incidence, we conducted populationbased surveillance for acute febrile illness (AFI) in Fayoum governorate (population 2 347 249), Egypt during two summer periods (2002 and 2003). All hospitals and a representative sample of community healthcare providers were included. AFI patients without obvious etiology were tested for brucellosis by culture and serology. Incidence estimates were calculated adjusting for sampling methodology and study period. Of 4490 AFI patients enrolled, 321 (7%) met the brucellosis case definition. The estimated annual incidence of brucellosis per 100 000 population was 64 and 70 in 2002 and 2003, respectively. The median age of brucellosis patients was 26 years and 70% were male; 53% were initially diagnosed as typhoid fever. Close contact with animals and consumption of unpasteurized milk products were associated with brucellosis. The high incidence of brucellosis in Fayoum highlights its public health importance, and the need to implement prevention strategies in humans and animals. © 2007 Royal Society of Tropical Medicine and Hygiene. Published by Elsevier Ltd. All rights reserved.
1. Introduction ∗ Corresponding author. Present address: NAMRU-3, PSC 452 Box 5000 (code 304), FPO AE 09835, Egypt. Tel.: +11 202 276 5287; fax: +11 202 276 5414. E-mail address: [email protected] (F.J. Mahoney).
Brucellosis is a zoonotic disease that is widely distributed throughout the developing world. In 1992, WHO reported that 86 (49%) out of 175 countries were affected, with an estimated population at risk of 2.4 billion persons (WHO,
0035-9203/$ — see front matter © 2007 Royal Society of Tropical Medicine and Hygiene. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.trstmh.2007.02.027
708 1996). Surveillance data suggest that brucellosis incidence is increasing in many countries of the Mediterranean Region and the Middle East (WHO, 1997). However, it is not clear whether the increase reflects improved surveillance and better recognition of disease or a true increase in disease incidence. Estimates of brucellosis incidence in Egypt are based primarily on surveillance data reported from infectious disease hospitals (n = 108) throughout the country. Data from these hospitals indicate considerable variations in disease incidence by region, with rates ranging from 0.2 to 26/100 000 (data from National Information Center for Health and Population). The diagnosis of brucellosis in this surveillance system is based almost entirely on clinical criteria with little laboratory confirmation of disease. Laboratory-based surveillance among patients with acute febrile illness (AFI) admitted to infectious disease hospitals throughout Egypt reported that 11% of patients had evidence of acute brucellosis (Afifi et al., 2005). While these data indicate that brucellosis is widespread in Egypt, there is little reliable information on disease incidence. To better characterize the epidemiology of dis-
G.J. Jennings et al. ease and better define disease burden, population-based surveillance for patients with AFI was established in Fayoum Governorate (population 2.3 million). This paper summarizes the results of surveillance activities over a 2 year period and discusses the implications of these studies for public health control measures.
2. Materials and methods Fayoum Governorate, located ∼100 km southwest of Cairo (Figure 1), is geographically isolated by desert, which limits population mobility, making it a suitable site for population-based surveillance. The governorate is divided into six administrative districts and is largely agrarian, with a total estimated population of 2 347 249. Population-based surveillance for patients with AFI was conducted in two time periods, including June to October 2002 and June to October 2003. Case-finding methods involved recruitment of a representative sample of primary care providers from all tiers of health service in the study area. These tiers included the infectious disease hospital, all six district general hospitals, all infectious disease or ‘fever’ specialists and a random sample of rural health units and primary care providers. We defined primary care providers as general practitioners, internal medicine physicians or pediatricians. In 2002, approximately 10% of rural health units (13/138) and primary care providers (18/186) participated in the surveillance. All providers were randomly selected from a comprehensive roster of practicing physicians in the catchment area. Provider enrollment was expanded to 20% in 2003, to obtain better estimates of disease incidence at the district level. None of the selected primary care providers refused to participate in this study.
2.1. Case definitions AFI was defined as any individual ≥1 year of age with a temperature greater than 38 ◦ C at the time of visit, or history of fever of more than 2 d duration, and no identified cause of fever such as diarrhea, hepatitis and respiratory tract infections, or alternatively any patient with a clinical diagnosis of typhoid fever or brucellosis. A case of brucellosis was defined as an AFI patient with laboratory-confirmed brucellosis, established by the isolation of Brucella spp. from blood culture or a serologic titer ≥1:320 by the tube agglutination test.
2.2. Data collection
Figure 1 (A) Location of Fayoum Governorate, ∼100 km southwest of Cairo, Egypt. (B) Brucellosis incidence for 2003 for Fayoum Governorate and its six administrative districts.
All patients meeting the case definition of AFI were invited to participate in the study. Providers were trained to conduct a standardized clinical and laboratory evaluation, including collection of blood cultures and serum samples at the time of clinical evaluation. Data from consenting patients were collected using a brief, standardized questionnaire that included information on demographic and clinical characteristics. In 2003, questions were added to the questionnaire regarding antibiotic use, occupation and animal exposures.
Brucellosis as a cause of acute febrile illness in Egypt
2.3. Incidence calculations We calculated the incidence of brucellosis after considering the provider-sampling scheme, diagnostic test sensitivity and specificity and duration of sampling (Crump et al., 2003). To account for provider sampling, we derived a representative arithmetic multiplier for each of the five tiers of healthcare providers. In 2002, 89% of fever specialists were enrolled for a multiplier of 1.1. In 2003, 93% of fever specialists were enrolled for a multiplier of 1.1. In 2002, 9.4% of rural health units and 9.7% of primary care providers were enrolled for multipliers of 10.6 and 10.3, respectively. In 2003, 19.4% of rural health units participated for a multiplier of 5.2, and 18.5% of primary care providers were enrolled for a multiplier of 5.4. Because the majority of brucellosis cases can be detected with a combination of blood culture and serology, we assumed that test sensitivity approached 100%; consequently we used a multiplier of one. To adjust the 20 week study period to represent an entire year, we multiplied the number of patients with brucellosis identified during surveillance by 2.6 (Table 1) using estimates of seasonality based on the monthly distribution of hospitalized patients with brucellosis in Egypt from 1999 to 2003 (Afifi et al., 2005).
2.4. Statistical analysis Data were double-entered into a Microsoft Access database. Population incidence was calculated using annualized census estimates. To characterize risk factors for disease, we compared brucellosis patients with other AFI patients who were culture negative for typhoid fever. Basic descriptive analysis of demographic data and age-adjusted prevalence ratios were calculated using Epi Info 2000 (CDC, Atlanta, GA, USA). A P-value <0.05 was considered statistically significant.
2.5. Clinical and laboratory methods Healthcare providers were supplied with materials for venipuncture and blood culture and trained in sterile collection techniques. The patients’ blood was inoculated into a biphasic blood culture bottle (bioMerieux, Marcy l’Etoile, France) by the attending physician. Serum samples were processed on the day of collection and testing was performed at the Fayoum Infectious Disease Hospital or Fayoum Governorate General Common Laboratory. Standard tube
Table 1
709 agglutination (STA) was performed following the manufacturer’s instructions (SA Scientific Inc., San Antonio, TX, USA) using antigen for B. abortus (strain USDA #1119-3). Agglutination titers of ≥1:320 were considered positive (Young, 1995). Blood culture bottles were incubated at 37 ◦ C for 5 d and observed daily for signs of bacterial growth in either the liquid or solid phase. An aliquot from any blood culture bottle with suspected growth was transferred to blood, chocolate and MacConkey Agar for bacterial isolation and characterization. All blood culture bottles were transferred to a referral laboratory at NAMRU-3 after 5 d incubation, and maintained at 37 ◦ C for an additional 21 d in order to monitor for growth of Brucella spp. Speciation of Brucella isolates was conducted using PCR primers and conditions developed by Bricker and Halling (1994). As a performance indicator, contamination rates of blood cultures were monitored and additional training provided when necessary. All cultured bacteria and serology results obtained at laboratories in Fayoum Governorate were confirmed at NAMRU-3.
3. Results In total, 4490 patients with AFI were evaluated in 2002 and 2003, and of these 321 (7.2%) met the case definition for brucellosis. In 2002, 135 patients had laboratory-confirmed brucellosis, with an estimated incidence of 64/100 000, while in 2003, 186 patients had laboratory-confirmed disease, with an estimated incidence of 70/100 000 (Table 1). In 2003, brucellosis incidence rates varied widely between districts, and ranged from 38/100 000 in El-Fayoum to 181/100 000 in Tamiya (Figure 1). Of the 321 patients with laboratory-confirmed brucellosis, 115 (36%) were diagnosed by culture and 206 (64%) were diagnosed by serology only. Other pathogens isolated included Salmonella typhi (n = 264), Staphylococcus aureus (n = 10), Escherichia coli (n = 6), other Salmonella species (n = 3), Enterobacter species (n = 2) and Streptococcus pneumonia (1). Among patients with culture-confirmed S. typhi infection, only 2 (0.8%) had Brucella tube agglutination titers ≥1:320. Among the 115 patients with cultureconfirmed brucellosis, 15 (13%) had titers below the cutoff (1:320). The overall contamination rate (mainly skin flora) decreased from 18.0% (320) in 2002 to 9% (239) in 2003. The species of 114 Fayoum Brucella isolates characterized
Brucellosis incidence estimates for Fayoum Governorate in 2002 and 2003, showing five tiers of healthcare providersa
Year Healthcare provider
2002 2003 a
Test sensitivity multiplier
Fever hospital
District hospital
Rural Fever Primary care Total health unit specialist provider
21(21) 11(11)
17 (17) 19 (19)
18 (187) 28 (144)
52 (58) 55 (59)
27 (279) 73 (395)
135 (562) 1 186 (628) 1
Time frame
Total cases
Incidence/ 100 000
2.6 2.6
1772 1897
64 70
The number of patients identified by healthcare providers at each sampling tier are multiplied by the provider multiplier (total no. providers/no. providers enrolled) to yield the adjusted number of cases (in brackets). Because the vast majority of brucellosis cases can be detected with the combination of blood culture and the tube agglutination assay, we did not apply a multiplier to account for test sensitivity. A time frame multiplier of 2.6 was used for the 20-week study period based on seasonality of disease and the reporting period. The total number of adjusted cases was divided by the population to yield the incidence.
710
G.J. Jennings et al.
by PCR identified 113 (99%) as B. melitensis and a single B. abortus.
soft cheeses or yogurt) was also associated with increased risk.
3.1. Demographic characteristics and exposures
3.2. Clinical characteristics
The majority of brucellosis patients were male (70%) with a median age (25 years) that was significantly higher than the age of patients with S. typhi infection. There were no significant differences in the age and gender distribution of patients with culture-confirmed disease when compared to patients confirmed by serology alone (Table 2). Disease incidence among children 0—9 years of age was sevenfold lower than other age groups (Table 3). Patients with brucellosis reported a variety of exposures commonly associated with Brucella infections (Table 4), including close contact with buffalo, cattle and sheep. In addition, brucellosis patients were more likely to be farmers or involved in animal husbandry. Consumption of unpasteurized dairy products (e.g.
The distribution of clinical signs and symptoms was similar among patients with culture- and serologically-confirmed disease. The most common presenting signs and symptoms included history of fever greater than 2 d duration (99%), headache (86%), fever at time of presentation (82%), arthralgia (75%), undulating fever (58%) and abdominal pain (57%). Generally, the clinical features of brucellosis patients were similar to those of other AFI patients (including typhoid), except for undulating fever and arthralgias, which occurred with significantly greater frequency among brucellosis patients (P < 0.05). In addition, patients with brucellosis tended to wait longer than other AFI patients before seeking medical care (median time of 7 vs. 4 d). Brucellosis
Table 2 Selected demographic and clinical characteristics of brucellosis patients, population-based surveillance, Fayoum Governorate, Egypt, 2002—2003 Characteristic
Laboratory-based diagnosis Culture-confirmed brucellosis (n = 115)
Median (range) age (years) Males (%) Median days fever before medical care Mean duration of fever Headache (%) Abdominal pain (%) Undulant fever (%) Arthralgia (%)a Rash (%) Nausea (%) Vomiting (%) No. (%) treated with antibiotics No. (%) treated with more than one antibiotic
Culture-negative AFI (n = 3524)
Brucellosis confirmed by serology (n = 206)
Culture-confirmed typhoid (n = 264)
25.5 (3—70) 142 (69) 6
11 (2—54) 146 (55) 5
20 (1—100) 2144 (61) 4
11.4 101 (88) 69 (60) 66 (57) 54 (75) 6 (5) 46 (40) 31 (27) 73 (64)
10.2 176 (85) 113 (55) 120 (58) 85 (75) 16 (8) 88 (46) 75 (36) 142 (69)
7.5 215 (81) 182 (70) 111 (42) 94 (57) 12 (5) 106 (40) 108 (41) 175 (66)
6.2 3037 (86) 2426 (69) 1445 (41) 1472 (70) 0 1605 (46) 1332 (38) 2333 (66)
68 (59)
128 (62)
171 (65)
1861 (53)
22 (1—62) 81 (70) 6
AFI: acute febrile illness. a Data on arthralgia were not collected in 2002.
Table 3
Annual incidence rates of brucellosis by age group, Fayoum 2003a
Age group (years) 0—9 10—19 20—39 ≥40 Total a
No. cases 8 61 69 48 186
Adjusted no. cases
Population
Incidence/100 000 year
29.6 205 231 163
674 112 618 315 620 392 434 430
11 86 97 97
629
2 347 249
70
Patients identified by healthcare providers at each sampling tier were stratified into four age groups and multiplied by the provider multiplier (total no. providers/no. providers enrolled) to determine the adjusted number of cases. Incidence was calculated by dividing the number of adjusted cases by the estimated age-specific population for each age group (population data provided by the National Information Center for Health and Population).
Brucellosis as a cause of acute febrile illness in Egypt
711
Table 4 Comparison of various relevant exposures between patients with brucellosis and patients with other acute febrile illnesses; univariate analysis, population-based surveillance, Fayoum Governorate, Egypt, 2003 Exposure Cattle Farm work Buffalo Contact with an aborted animal fetus Soft cheese or yogurt Slaughter Sheep Raw milk a b
No. (%) cases exposed (n = 186)a
No. (%) non-brucellosis patients exposed (n = 2320)a
Age-adjusted prevalence ratio
95% CLb
65 (35) 64 (34) 70 (38) 36 (20)
540 (23) 402 (17) 479 (21) 218 (9)
2.1 2.0 2.0 2.0
1.2—2.1 1.5—2.6 1.5—2.6 1.4—2.8
160 (86) 42 (23) 41 (22) 92 (50)
1796 (78) 327 (14) 333 (14) 984 (43)
1.6 1.5 1.5 1.3
1.1—2.4 1.1—2.1 1.0—2.0 0.96—1.7
Analysis was done for patients evaluated in 2003 only. 95% confidence limit; P < 0.05.
was the initial clinical diagnosis for 30% of patients with laboratory-confirmed disease, while 53% of these patients were initially misdiagnosed as having typhoid fever. The most common clinical diagnosis was fever of unknown origin (19%). The majority of brucellosis patients (83%) were managed in the outpatient setting; only 6% were detected at the infectious disease hospital. The use of antibiotics to treat brucellosis patients increased from 79 (58%) in 2002 to 133 (71%) in 2003. Among 271 patients with an initial diagnosis of brucellosis, the most commonly prescribed antibiotics were trimethoprim—sulfamethoxazole (22%) followed by chloramphenicol (19%), ciprofloxacin (15%), aminoglycosides (9%) and ampicillin (8%). In 2003, doxycycline, rifampicin and streptomycin were added to the list of antibiotics prescribed on the surveillance form. Physicians did not report prescribing any of these drugs in 2003. Only 24% of brucellosis patients received more than one antibiotic for initial treatment of their infection. We observed no significant differences in antibiotic treatment among patients who received inpatient care as opposed to patients who were diagnosed in an outpatient setting (i.e. primary care physicians, rural health units or fever specialists).
4. Discussion This population-based surveillance study provides estimates on the incidence of brucellosis in a well defined population in Fayoum Governorate, thus highlighting the public health importance of this disease in Egypt. These data also revealed that brucellosis is not well recognized as a common cause of AFI, which has important implications for clinical management and public health control measures. The present study was designed to define the disease burden associated with brucellosis in a rural Egyptian governorate. Only 5.7% of brucellosis patients were identified by hospital-based surveillance. If these hospitalized patients were used to calculate disease incidence, the rate would be 3.8/100 000 using a case definition based on laboratory confirmation or 6.0/100 000 if the case definition
were based upon clinical presentation alone. In this study, the laboratory criteria used for the serologic diagnosis of brucellosis (tube agglutination titers ≥1:320) are more stringent than those recommended by WHO (titers >1:160, WHO/CDS/CSR/ISR/99.2), thus the incidence may actually under-represent overall burden of disease. Although this study focused on Fayoum Governorate, studies of AFI patients have found that brucellosis is a common cause of disease in all parts of Egypt. In a study of hospitalized patients with AFI in diverse regions of the country, 12 to 40% had laboratory-confirmed brucellosis (Afifi et al., 2005). These data also suggest that disease is prevalent in both urban and rural settings in all parts of the country. As brucellosis is usually transmitted through exposure to infected animals or consumption of contaminated products, these studies imply that Brucella infection in domestic animals is widespread in Egypt (Refai, 2002). The incidence rates observed in Fayoum Governorate are consistent with those reported throughout the Middle East, which range from 8/100 000 in the Gaza Strip (Awad, 1998; Memish, 2001) to 40/100 000 in Saudi Arabia (Memish, 2001), 46/100 000 in Jordan (Dajani et al., 1989) and 85/100 000 in Kuwait (Mousa et al., 1987). A recent population-based serosurvey in southern Saudi Arabia demonstrated serological evidence of past exposure to Brucella among 20% of the population, with more than 2% having evidence of active disease (Alballa, 1995). Although brucellosis is recognized as a common cause of AFI in various parts of Egypt, this study revealed that it is often misdiagnosed and mistreated. More than half of all brucellosis cases were misdiagnosed as typhoid, and only a quarter of them received treatment with more than one antibiotic. We could not assess duration of therapy in this study. However, well-established clinical guidelines for management of brucellosis require treatment with two antibiotics for a minimum of 6 weeks in order to minimize the risk of relapse (Hall, 1990; Solera et al., 1997). It is therefore important to educate physicians in Egypt about proper treatment of brucellosis, and to develop national treatment guidelines. Furthermore, it is important to improve laboratory capacities available to physicians in Egypt in order to better diagnose brucellosis, especially as
712 the clinical presentation of this disease is relatively nonspecific. In the current study, we found that the majority of brucellosis patients were adult males, with approximately one-third citing their principle occupation as farmer. Exposures associated with infection included close contact with sheep, cattle or buffalo, exposure to an animal abortus (aborted fetus) and consumption of dairy products such as soft cheeses and yogurt. As these dairy products are often unpasteurized and produced locally, they represent a plausible source of infection. Consumption of raw milk was not identified as a risk factor for disease. However, this exposure was quite common among other AFI patients as well, indicating that a much larger sample would be needed to demonstrate a significant association. The current study was not designed to evaluate the proportion of brucellosis attributable to food versus animal exposures, and it is difficult to evaluate the potential impact of different prevention strategies. Better risk factor studies are needed to assess attributable risk due to these different exposures. Despite this limitation, the high frequency of exposures associated with well-defined risk factors highlights the need for extensive efforts to educate the population regarding potential food- and animal husbandry-related exposures. In addition to the hazard it represents to human health, Brucella infection has a considerable economic impact on animal husbandry, including significant loss in agricultural productivity due to abortions, sterility, decreased milk production and costs associated with veterinary care (Roth et al., 2003). In addition, the disease can be an impediment to animal movement and exportation. To better define the economic impact of disease, quality data are needed on the prevalence of disease in livestock populations, and estimates of control costs to both producers and consumers. However, surveillance and control of brucellosis in Egypt and other countries in the Eastern Mediterranean Region are complex, due to the diversity of domestic animal species that are infected, different modes of transmission from animals to humans, and the challenges of disease control. Animal husbandry is the primary occupation for a large sector of the rural population in Egypt, where the livestock population includes 2.8 million cattle, 3.2 million buffalo, 3.7 million sheep, 2.9 million goats and 220 000 camels (Refai, 2002). Seroprevalence studies of domestic animals indicate that Brucella infection rates vary widely among different species and in different parts of the country (A. El-Taweel, unpublished data; A.M. Montasser, unpublished data) (Refai, 2002). Vaccination of livestock populations is a well-recognized and agreed-upon strategy for control of brucellosis. However, delivery strategies are challenging, particularly in the Middle East, with diversity of species distributed over wide geographic regions. In Egypt, animal husbandry practices include close contact among different species; thus control programs targeting one species are likely to have a limited impact. In this project, B. melitensis was, with a single exception, the only species isolated. Brucella melitensis is typically associated with sheep and goats; however, the species is being increasingly recognized as a source of infection for both cattle and buffalo (Corbel, 1997; Hamdy and Amin, 2002; Stevens et al., 1994). The predominance of B. meliten-
G.J. Jennings et al. sis as a cause of disease in humans suggests that it has adapted to cattle and buffalo in Egypt, as exposure to these animals and their dairy products has been recognized as a source of infection. This cross-species adaptation creates a challenge to vaccination strategies, because vaccines such as Rev1 were developed to combat B. melitensis infection in sheep and goats (Zygmunt et al., 1994), while RB51 and Strain 19 were developed to reduce infection by B. abortus in cattle (Stevens et al., 1995). The use and efficacy of these vaccines in alternate hosts requires additional investigation (Denes, 1997). Coupled with the uncertainty regarding vaccine effectiveness is the uncertainty of program effectiveness. Considerable resources and program experience are necessary to implement and sustain animal vaccination programs with substantial investment from both the public and private sector. Experience in many countries suggests that it can take decades to eradicate brucellosis with a combined strategy of vaccination followed by test and slaughter activities. To establish an economic framework for such an investment, it is recommended that veterinary and national health authorities work together to evaluate available data on disease burden and cost-effectiveness of control strategies. Given the challenges of implementing control programs in animals, it is recommended that national health authorities and veterinary services work together to ensure pasteurization of commercial dairy products, increase public awareness of brucellosis and minimize high-risk occupational and domestic exposures such as handling an abortus. In addition, efforts are needed to educate clinicians on recognition of disease, to establish laboratory capacity to confirm the diagnosis and to ensure availability of appropriate antibiotics for treatment. Disclaimer: The opinions and assertions contained herein are the private ones of the authors and are not to be construed as official or reflecting the views of the Navy Department, Department of Defense, the U.S. Government, or the Egyptian Ministry of Health and Population. Authors’ contributions: GJJ, RAH, KE and FJM conceptualized and designed the study; FYG, PS, NES and SPL carried out the clinical assessments; MAF, MAM and MOW carried out the immunoassays and microbiological examination; GJJ, RAH, KE, MOW and FJM drafted the manuscript. All authors read and approved the final manuscript. FJM is guarantor of the paper. Acknowledgements: We would like to acknowledge the Fayoum Governorate Health Directorate and the physicians and laboratory personnel at hospitals and clinics in Fayoum Governorate for their valuable contributions to this surveillance study. We would also like to recognize Mr Muhammad El Mofty and Mohammed Adel for their valuable assistance in managing the Fayoum data and Dr Guillermo Pimentel for assistance during manuscript preparation. Funding: Global Emerging Infections Surveillance System, United States Department of Defense, and the US Agency for International Development, work unit #847705.82000.25GB.E0018.
Brucellosis as a cause of acute febrile illness in Egypt Conflict of interest: None declared. Ethical approval: Institutional review boards of NAMRU-3 and the US Centers for Disease Control and Prevention.
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