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Persistence of West Nile Virus (WNV) IgM antibodies in cerebrospinal fluid from patients with CNS disease
Journal of Clinical Virology 31 (2004) 289–291
Persistence of West Nile Virus (WNV) IgM antibodies in cerebrospinal fluid from patients with CNS disease Hema Kapoora∗ , Kimberly Signsb , Patricia Somsela , Frances P. Downesa , Patricia A. Clarka , Jeffrey P. Masseya a
Bureau of Laboratory, Michigan Department of Community Health (MDCH), 3350 N MLK Blvd, Lansing, MI 48909, USA b Bureau of Epidemiology, Michigan Department of Community Health (MDCH), Lansing, MI 48909, USA Received in revised form 24 May 2004; accepted 28 May 2004
Abstract The Michigan Department of Community Health (MDCH) reported 644 laboratory positive human cases of West Nile Virus (WNV) in the 2002 outbreak in the US, of which 559 cases presented with either meningitis or encephalitis. The first line test utilized for diagnosis of WNV infection was the immunoglobulin M (IgM)-capture enzyme-linked immunosorbent assay (MAC-ELISA). We continued testing for WNV even during winter months of the year 2002–2003 due to the awareness of other modes of WNV transmission (blood transfusion, organ transplantation, transplacental, breast milk, and occupational) as well as concern for people traveling to endemic areas. As a result of year-round testing for WNV infections during 2002–2003, we detected WNV IgM-specific antibodies in cerebrospinal fluid (CSF) specimens from three patients persisting for 110, 141, and 199 days post acute phase infection in patients with central nervous system (CNS) disease. This is a new observation and there is no published data on the persistence of WNV IgM antibodies in CSF specimens beyond 47 days. Thus, it is important to note that the presence of WNV IgM class antibodies may not always reflect acute phase infection with this virus. © 2004 Elsevier B.V. All rights reserved. Keywords: West Nile Virus; Persistence; Cerebrospinal fluid
1. Introduction The first outbreak of West Nile Virus (WNV) in the United States was seen in the New York City area in 1999 (Anderson et al., 1999; Asnis et al., 2000; Briese et al., 1999; Jia et al., 1999; Lanciotti et al., 1999; Nash et al., 2001). In 2002, increasing WNV activity was reported widely throughout the United States (CDC, 2002a). Diagnosis of WNV encephalitis is primarily established if WNV-specific immunoglobulin M (IgM) antibodies are found in cerebrospinal fluid (CSF) using IgM-capture
Abbreviations: WNV, West Nile Virus; CNS, Central nervous system; MAC-ELISA, IgM-capture enzyme-linked immunosorbent assay; EEE, Eastern Equine encephalitis; CGV, California group (LaCrosse) encephalitis; SLE, St. Louis encephalitis ∗ Corresponding author. Tel.: +1 517 335 8099; fax: +1 517 335 9631. E-mail address: [email protected] (H. Kapoora ). 1386-6532/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jcv.2004.05.017
enzyme-linked immunosorbent assay (MAC-ELISA) tests (Martin et al., 2000). Virus also might be isolated (rarely) or detected by RT-PCR (in up to 60% of cases) in acute-phase CSF samples. Longitudinal studies of WNV meningitis and encephalitis cases have demonstrated that WNV-specific IgM antibody can persist in serum for 12 months or longer (John et al., 2003). This group did not follow longitudinally the WNVreactive IgM activity in CSF and the latest WNV-positive CSF specimen ever submitted to the Center for Disease Control and Prevention for diagnostic testing from a laboratoryconfirmed WNV human infection was obtained at 47 days after onset (data not shown). More than 2900 specimens were tested at Michigan Department of Community Health (MDCH) for WNV, Eastern Equine encephalitis (EEE), California group (LaCrosse) encephalitis (CGV) and St. Louis encephalitis (SLE) by
290
H. Kapoor et al. / Journal of Clinical Virology 31 (2004) 289–291
serology in 2002, and 644 laboratory-positive cases of WNV were detected, of which 559 were either meningitis or encephalitis. We performed PCR for WNV only in cases of special interest like transfusion associated, breast milk transmission, postmortem tissues or in a research setting. Following the nation-wide outbreak of WNV in 2002 and due to awareness of other modes of WNV transmission (CDC, 2002b, 2002c, 2002d, 2002e, 2002f; Pealer et al., 2003), we instituted year-round testing for WNV. During the post seasonal period from November 1, 2002 to April 30, 2003, 147 CSF specimens were tested for WNV IgM. Only three CSF samples out of these 147 were found positive for WNV IgM antibodies. It was observed that these were the second CSF specimens from cases previously confirmed by our laboratory during the outbreak. We investigated these cases for the persistence of IgM antibodies and virus as well as level of neutralizing antibodies.
2. Methods Cerebrospinal fluids submitted for arbovirus panel testing were analyzed for the presence of IgM antibodies for WNV, EEE, SLE, and CGV using antibody capture ELISA also known as MAC-ELISA (Martin et al., 2000). This test was performed in singlet and the positive tests were repeated in duplicate. Results were expressed as a P/N value, which was calculated by dividing the optical density (OD) of the patient’s CSF antigen well (P) by the average OD of the normal human antigen wells (N). A P/N of ≤2.0 was considered negative. The specimens with repeat P/N values from 2 to 10 were considered equivocal and ≥10 are considered positive (Kapoor et al., 2003). In all three cases discussed, the P/N ratio for WNV was at least three times the P/N ratio for SLE virus, indicating a WNV infection (Martin et al., 2002). Plaque reduction neutralization test (PRNT) was performed as per a CDC recommended procedure to confirm the presence of neutralizing antibodies. For detection of persistence of virus in these specimens, fluorogenic 5 nuclease RT-PCR was performed using the ABI PRISM 7000 (Applied Biosystems, Foster City, CA) as previously described (Lanciotti, 2000). Rapid-cycle real-time
RT-PCR was performed using the primer set 10668/10770c and probe10692-FAM/TAMRA in the primary screen for viral RNA. For confirmatory purposes, positive samples were tested by a secondary assay using the 1160/1229c primer set and probe 1186-FAM/TAMRA. Samples that tested positive for both assays were considered confirmed positives.
3. Results All three cases of CNS disease were hospitalized with a history of fever >38.5 ◦ C, weakness of extremities, altered mental status, pleocytosis and had a prolonged and incomplete recovery from the illness. One out of the three cases had associated cortical blindness. There was no history of travel or vaccination for Yellow Fever or Japanese encephalitis. All cases were diagnosed for West Nile virus infection while in the acute stage of the illness by demonstration of WNVspecific IgM antibodies in clear non-bloody CSF specimens. No cross-reactions with SLE IgM antibodies were observed and IgM antibodies for EEE and CGV were negative in all of the three cases. Results of persistence of these IgM antibodies for WNV, confirmation of these findings by PRNT and absence of virus are depicted in Table 1.
4. Discussion The laboratory criteria for defining a case of WNV encephalitis or meningitis by CDC (2003) specify, presence of a compatible clinical syndrome and demonstration of virusspecific IgM antibodies in CSF by antibody-capture enzyme immunoassay (EIA). Only in cases where CSF specimen is not available or cases which present like WNV fever, a fourfold or greater change in virus-specific serum antibody titer is done. Since we observed the presence of WNV-specific IgM antibodies in high titers in non-traumatic CSF specimens as early as 2 days after the onset of the disease, serum antibodies were not looked for. Tardei et al. (2000) reported that WNV IgM in CSF appears before it does in serum, indicating that the antibody production begins locally in the CNS and
Table 1 Serological and nucleic acid amplification results for West Nile virus on cerebrospinal fluids by days after onseta Case number
Days after onset
1
6 110 2 141 2 199
2 3
IgM-capture ELISA
Plaque reduction neutralization test
WNV (P/N)
SLE
WNV
SLE
90.0 72.5 42.5 95.9 153 159
7.0 3.2 7.1 8.06 17.1 Not tested
1:2 1:32 NA 1:4 NA 1:4
Neg Neg NA Neg NA Neg
PCR
Neg Neg NA Neg NA Neg
A P/N of ≤2.0 was considered negative. The specimens with repeat P/N values from 2 to 10 were considered equivocal and ≥10 are considered positive. a IgM, immunoglobulin M; ELISA-enzyme linked immunoassay; WNV, West Nile virus; SLE, St. Louis encephalitis; PCR, polymerase chain; NA, not available.
H. Kapoor et al. / Journal of Clinical Virology 31 (2004) 289–291
that its presence did not merely reflect transudation from the systemic circulation. We investigated for the persistence of neutralizing antibodies and, in one of the cases, there was a four-fold increase in the titer. Poland et al. (1981) demonstrated persistence of neutralizing antibodies for 30–35 years after Yellow Fever vaccine. Persistence of IgM antibodies in serum samples has been documented from the outbreak in New York City, lasting as long as 525 days (17.5 months) after onset (John et al., 2003), and makes testing of single serum samples in endemic areas problematic. It is challenging to conduct studies for persistence of immunoglobulins in CSF because of the difficulty of obtaining sequential CSF specimens. The longest reported persistent WNV positive CSF specimen submitted to CDC for diagnostic testing from a laboratory was reported on a specimen collected 47 days after onset (John et al., 2003). The longest persistence of WNV IgM we observed was 199 days post onset of symptoms, a length of persistence that has not been previously documented. This suggests the possibility that WNV IgM antibodies in a CSF specimen seen during a non-transmission season (CDC, 2002a; John et al., 2003; Petersen and Roehrig, 2001) may be the persisting WNV IgM antibodies from CNS infection, which occurred in the previous transmission season, especially in patients who have had persistent symptoms. While IgM antibodies usually indicate a recent infection, WNV IgM antibodies in CSF during the non-transmission season may be persisting from an infection acquired in the past season. Therefore, a judicious interpretation of positive WNV IgM antibody results in a CSF sample is required if testing is performed during non-transmission season from early November to end of April. We conclude that IgM antibodies for WNV may persist in CSF as long as 199 days post onset of illness. However, the reason for this persistence of IgM antibodies in CSF and rising titer of neutralizing antibodies with no evidence of virus needs more investigation in a research setting.
Acknowledgements This work was in part supported by Center for Disease Control for WNV Surveillance Laboratory EPI grant (#U50/CCU514403-05-2) awarded to State of Michigan. The authors thank our laboratory staff, epidemiology colleagues and Dr. Duane Newton PhD, University of Michigan, Ann Arbor, MI for providing information on the case #1 and 3.
References Anderson JF, Andreadis TG, Vossbrinck CR, et al. Isolation of West Nile virus from mosquitoes, crows, and a Cooper’s hawk in Connecticut. Science 1999;286:2331–3.
291
Asnis DS, Conetta R, Teixeira AA, Waldman G, Sampson BA. The West Nile virus outbreak of 1999 in New York: the Flushing Hospital experience. Clin Infect Dis 2000;30:413–8. Briese T, Jia XY, Huang C, Grady LJ, Lipkin WI. Identification of a Kunjin/West Nile-like flavivirus in brains of patients with New York encephalitis. Lancet 1999;354:1261–2. Centers for Disease Control and Prevention (CDC). West Nile virus activity—United States, July 31–August 7, 2002 and Louisiana, January 1–August 7, 2002. Morb Mortal Wkly Rep 2002a;51(31):681–3. Centers for Disease Control and Prevention (CDC). Acute flaccid paralysis syndrome associated with West Nile virus infection—Mississippi and Louisiana, July–August 2002. Morb Mortal Wkly Rep 2002b;51(37):825–8. Centers for Disease Control and Prevention (CDC). Possible West Nile virus transmission to an infant through breast feeding—Michigan, 2002. Morb Mortal Wkly Rep 2002c;51(39):877–8. Centers for Disease Control and Prevention (CDC). Update: investigations of West Nile virus infections in recipients of organ transplantation and blood transfusion—Michigan, 2002. Morb Mortal Wkly Rep 2002d;51(39):879. Centers for Disease Control and Prevention (CDC). Provisional Surveillance Summary of the West Nile Virus Epidemic—United States, January–November 2002. Morb Mortal Wkly Rep 2002e;51:1129–32. Centers for Disease Control and Prevention (CDC). Intrauterine West Nile virus infection—New York, 2002. Morb Mortal Wkly Rep 2002f;51(50):1135–6. Centers for Disease Control and Prevention (CDC). Epidemic/Epizootic West Nile Virus in the United States: Guidelines for Surveillance, Prevention, and Control. Fort Collins, Colorado: Division of VectorBorne Infectious Diseases; 2003 [3rd revision]. Jia XY, Briese T, Jordan I, et al. Genetic analysis of West Nile New York 1999 encephalitis virus. Lancet 1999;354:1971–2. John TR, Nash D, Maldin B, et al. Persistence of virus-reactive serum immunoglobulin m antibody in confirmed West Nile virus Encephalitis cases. EID 2003;9(3):376–9. Kapoor, H., Manning, S.D., Clark, P., et al., 2003. Laboratory evaluation of a West Nile virus (WNV) outbreak in Michigan. Abstracted in 19th Annual Clinical Virology Symposium and Annual Meeting Pan American Society for Clinical Virology, T 51. Lanciotti RS, Roehrig JT, Deubel V, et al. Origin of the West Nile virus responsible for an outbreak of encephalitis in the northeastern United States. Science 1999;286:2333. Lanciotti RS. Rapid detection of West Nile Virus from human clinical specimens, field-collected mosquitos, and avian samples by a TaqMan reverse transcriptase-PCR assay. J Clin Microbiol 2000;38:4066–71. Martin DA, Muth DA, Brown T, et al. Standardization of immunoglobulin M capture enzyme-linked immunosorbent assays for routine diagnosis of arboviral infections. J Clin Microbiol 2000;38:1823–6. Martin DA, Biggerstaff BJ, Allen B, et al. Use of immunoglobulin M cross-reactions in differential diagnosis of human flaviviral encephalitis infections in the United States. Clin Diagn Lab Immunol 2002;9:544–9. Nash D, Mostashari F, Fine A, et al. The outbreak of West Nile Virus infection in the New York City area in 1999 2001;344:1807–14. Pealer LN, Martin AA, Petersen LR, et al. Transmission of West Nile Virus through blood transfusuion in the United States in 2002 2003;349:1236–45. Petersen LR, Roehrig JT. West Nile virus: a reemerging global pathogen. EID 2001;7:611–4. Poland JD, Calisher CH, Monath WG, et al. Persistence of neutralizing antibody 30–35 years after immunization with 17D yellow fever vaccine. Bull WHO 1981;59:895–900. Tardei G, Ruta S, Chitu V, et al. Evaluation of immunoglobulin M (IgM) and IgG enzyme immunoassays in serologic diagnosis of West Nile virus infection. J Clin Microbiol 2000;38:2232–9.
Persistence of West Nile Virus (WNV) IgM antibodies in cerebrospinal fluid from patients with CNS disease Hema Kapoora∗ , Kimberly Signsb , Patricia Somsela , Frances P. Downesa , Patricia A. Clarka , Jeffrey P. Masseya a
Bureau of Laboratory, Michigan Department of Community Health (MDCH), 3350 N MLK Blvd, Lansing, MI 48909, USA b Bureau of Epidemiology, Michigan Department of Community Health (MDCH), Lansing, MI 48909, USA Received in revised form 24 May 2004; accepted 28 May 2004
Abstract The Michigan Department of Community Health (MDCH) reported 644 laboratory positive human cases of West Nile Virus (WNV) in the 2002 outbreak in the US, of which 559 cases presented with either meningitis or encephalitis. The first line test utilized for diagnosis of WNV infection was the immunoglobulin M (IgM)-capture enzyme-linked immunosorbent assay (MAC-ELISA). We continued testing for WNV even during winter months of the year 2002–2003 due to the awareness of other modes of WNV transmission (blood transfusion, organ transplantation, transplacental, breast milk, and occupational) as well as concern for people traveling to endemic areas. As a result of year-round testing for WNV infections during 2002–2003, we detected WNV IgM-specific antibodies in cerebrospinal fluid (CSF) specimens from three patients persisting for 110, 141, and 199 days post acute phase infection in patients with central nervous system (CNS) disease. This is a new observation and there is no published data on the persistence of WNV IgM antibodies in CSF specimens beyond 47 days. Thus, it is important to note that the presence of WNV IgM class antibodies may not always reflect acute phase infection with this virus. © 2004 Elsevier B.V. All rights reserved. Keywords: West Nile Virus; Persistence; Cerebrospinal fluid
1. Introduction The first outbreak of West Nile Virus (WNV) in the United States was seen in the New York City area in 1999 (Anderson et al., 1999; Asnis et al., 2000; Briese et al., 1999; Jia et al., 1999; Lanciotti et al., 1999; Nash et al., 2001). In 2002, increasing WNV activity was reported widely throughout the United States (CDC, 2002a). Diagnosis of WNV encephalitis is primarily established if WNV-specific immunoglobulin M (IgM) antibodies are found in cerebrospinal fluid (CSF) using IgM-capture
Abbreviations: WNV, West Nile Virus; CNS, Central nervous system; MAC-ELISA, IgM-capture enzyme-linked immunosorbent assay; EEE, Eastern Equine encephalitis; CGV, California group (LaCrosse) encephalitis; SLE, St. Louis encephalitis ∗ Corresponding author. Tel.: +1 517 335 8099; fax: +1 517 335 9631. E-mail address: [email protected] (H. Kapoora ). 1386-6532/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jcv.2004.05.017
enzyme-linked immunosorbent assay (MAC-ELISA) tests (Martin et al., 2000). Virus also might be isolated (rarely) or detected by RT-PCR (in up to 60% of cases) in acute-phase CSF samples. Longitudinal studies of WNV meningitis and encephalitis cases have demonstrated that WNV-specific IgM antibody can persist in serum for 12 months or longer (John et al., 2003). This group did not follow longitudinally the WNVreactive IgM activity in CSF and the latest WNV-positive CSF specimen ever submitted to the Center for Disease Control and Prevention for diagnostic testing from a laboratoryconfirmed WNV human infection was obtained at 47 days after onset (data not shown). More than 2900 specimens were tested at Michigan Department of Community Health (MDCH) for WNV, Eastern Equine encephalitis (EEE), California group (LaCrosse) encephalitis (CGV) and St. Louis encephalitis (SLE) by
290
H. Kapoor et al. / Journal of Clinical Virology 31 (2004) 289–291
serology in 2002, and 644 laboratory-positive cases of WNV were detected, of which 559 were either meningitis or encephalitis. We performed PCR for WNV only in cases of special interest like transfusion associated, breast milk transmission, postmortem tissues or in a research setting. Following the nation-wide outbreak of WNV in 2002 and due to awareness of other modes of WNV transmission (CDC, 2002b, 2002c, 2002d, 2002e, 2002f; Pealer et al., 2003), we instituted year-round testing for WNV. During the post seasonal period from November 1, 2002 to April 30, 2003, 147 CSF specimens were tested for WNV IgM. Only three CSF samples out of these 147 were found positive for WNV IgM antibodies. It was observed that these were the second CSF specimens from cases previously confirmed by our laboratory during the outbreak. We investigated these cases for the persistence of IgM antibodies and virus as well as level of neutralizing antibodies.
2. Methods Cerebrospinal fluids submitted for arbovirus panel testing were analyzed for the presence of IgM antibodies for WNV, EEE, SLE, and CGV using antibody capture ELISA also known as MAC-ELISA (Martin et al., 2000). This test was performed in singlet and the positive tests were repeated in duplicate. Results were expressed as a P/N value, which was calculated by dividing the optical density (OD) of the patient’s CSF antigen well (P) by the average OD of the normal human antigen wells (N). A P/N of ≤2.0 was considered negative. The specimens with repeat P/N values from 2 to 10 were considered equivocal and ≥10 are considered positive (Kapoor et al., 2003). In all three cases discussed, the P/N ratio for WNV was at least three times the P/N ratio for SLE virus, indicating a WNV infection (Martin et al., 2002). Plaque reduction neutralization test (PRNT) was performed as per a CDC recommended procedure to confirm the presence of neutralizing antibodies. For detection of persistence of virus in these specimens, fluorogenic 5 nuclease RT-PCR was performed using the ABI PRISM 7000 (Applied Biosystems, Foster City, CA) as previously described (Lanciotti, 2000). Rapid-cycle real-time
RT-PCR was performed using the primer set 10668/10770c and probe10692-FAM/TAMRA in the primary screen for viral RNA. For confirmatory purposes, positive samples were tested by a secondary assay using the 1160/1229c primer set and probe 1186-FAM/TAMRA. Samples that tested positive for both assays were considered confirmed positives.
3. Results All three cases of CNS disease were hospitalized with a history of fever >38.5 ◦ C, weakness of extremities, altered mental status, pleocytosis and had a prolonged and incomplete recovery from the illness. One out of the three cases had associated cortical blindness. There was no history of travel or vaccination for Yellow Fever or Japanese encephalitis. All cases were diagnosed for West Nile virus infection while in the acute stage of the illness by demonstration of WNVspecific IgM antibodies in clear non-bloody CSF specimens. No cross-reactions with SLE IgM antibodies were observed and IgM antibodies for EEE and CGV were negative in all of the three cases. Results of persistence of these IgM antibodies for WNV, confirmation of these findings by PRNT and absence of virus are depicted in Table 1.
4. Discussion The laboratory criteria for defining a case of WNV encephalitis or meningitis by CDC (2003) specify, presence of a compatible clinical syndrome and demonstration of virusspecific IgM antibodies in CSF by antibody-capture enzyme immunoassay (EIA). Only in cases where CSF specimen is not available or cases which present like WNV fever, a fourfold or greater change in virus-specific serum antibody titer is done. Since we observed the presence of WNV-specific IgM antibodies in high titers in non-traumatic CSF specimens as early as 2 days after the onset of the disease, serum antibodies were not looked for. Tardei et al. (2000) reported that WNV IgM in CSF appears before it does in serum, indicating that the antibody production begins locally in the CNS and
Table 1 Serological and nucleic acid amplification results for West Nile virus on cerebrospinal fluids by days after onseta Case number
Days after onset
1
6 110 2 141 2 199
2 3
IgM-capture ELISA
Plaque reduction neutralization test
WNV (P/N)
SLE
WNV
SLE
90.0 72.5 42.5 95.9 153 159
7.0 3.2 7.1 8.06 17.1 Not tested
1:2 1:32 NA 1:4 NA 1:4
Neg Neg NA Neg NA Neg
PCR
Neg Neg NA Neg NA Neg
A P/N of ≤2.0 was considered negative. The specimens with repeat P/N values from 2 to 10 were considered equivocal and ≥10 are considered positive. a IgM, immunoglobulin M; ELISA-enzyme linked immunoassay; WNV, West Nile virus; SLE, St. Louis encephalitis; PCR, polymerase chain; NA, not available.
H. Kapoor et al. / Journal of Clinical Virology 31 (2004) 289–291
that its presence did not merely reflect transudation from the systemic circulation. We investigated for the persistence of neutralizing antibodies and, in one of the cases, there was a four-fold increase in the titer. Poland et al. (1981) demonstrated persistence of neutralizing antibodies for 30–35 years after Yellow Fever vaccine. Persistence of IgM antibodies in serum samples has been documented from the outbreak in New York City, lasting as long as 525 days (17.5 months) after onset (John et al., 2003), and makes testing of single serum samples in endemic areas problematic. It is challenging to conduct studies for persistence of immunoglobulins in CSF because of the difficulty of obtaining sequential CSF specimens. The longest reported persistent WNV positive CSF specimen submitted to CDC for diagnostic testing from a laboratory was reported on a specimen collected 47 days after onset (John et al., 2003). The longest persistence of WNV IgM we observed was 199 days post onset of symptoms, a length of persistence that has not been previously documented. This suggests the possibility that WNV IgM antibodies in a CSF specimen seen during a non-transmission season (CDC, 2002a; John et al., 2003; Petersen and Roehrig, 2001) may be the persisting WNV IgM antibodies from CNS infection, which occurred in the previous transmission season, especially in patients who have had persistent symptoms. While IgM antibodies usually indicate a recent infection, WNV IgM antibodies in CSF during the non-transmission season may be persisting from an infection acquired in the past season. Therefore, a judicious interpretation of positive WNV IgM antibody results in a CSF sample is required if testing is performed during non-transmission season from early November to end of April. We conclude that IgM antibodies for WNV may persist in CSF as long as 199 days post onset of illness. However, the reason for this persistence of IgM antibodies in CSF and rising titer of neutralizing antibodies with no evidence of virus needs more investigation in a research setting.
Acknowledgements This work was in part supported by Center for Disease Control for WNV Surveillance Laboratory EPI grant (#U50/CCU514403-05-2) awarded to State of Michigan. The authors thank our laboratory staff, epidemiology colleagues and Dr. Duane Newton PhD, University of Michigan, Ann Arbor, MI for providing information on the case #1 and 3.
References Anderson JF, Andreadis TG, Vossbrinck CR, et al. Isolation of West Nile virus from mosquitoes, crows, and a Cooper’s hawk in Connecticut. Science 1999;286:2331–3.
291
Asnis DS, Conetta R, Teixeira AA, Waldman G, Sampson BA. The West Nile virus outbreak of 1999 in New York: the Flushing Hospital experience. Clin Infect Dis 2000;30:413–8. Briese T, Jia XY, Huang C, Grady LJ, Lipkin WI. Identification of a Kunjin/West Nile-like flavivirus in brains of patients with New York encephalitis. Lancet 1999;354:1261–2. Centers for Disease Control and Prevention (CDC). West Nile virus activity—United States, July 31–August 7, 2002 and Louisiana, January 1–August 7, 2002. Morb Mortal Wkly Rep 2002a;51(31):681–3. Centers for Disease Control and Prevention (CDC). Acute flaccid paralysis syndrome associated with West Nile virus infection—Mississippi and Louisiana, July–August 2002. Morb Mortal Wkly Rep 2002b;51(37):825–8. Centers for Disease Control and Prevention (CDC). Possible West Nile virus transmission to an infant through breast feeding—Michigan, 2002. Morb Mortal Wkly Rep 2002c;51(39):877–8. Centers for Disease Control and Prevention (CDC). Update: investigations of West Nile virus infections in recipients of organ transplantation and blood transfusion—Michigan, 2002. Morb Mortal Wkly Rep 2002d;51(39):879. Centers for Disease Control and Prevention (CDC). Provisional Surveillance Summary of the West Nile Virus Epidemic—United States, January–November 2002. Morb Mortal Wkly Rep 2002e;51:1129–32. Centers for Disease Control and Prevention (CDC). Intrauterine West Nile virus infection—New York, 2002. Morb Mortal Wkly Rep 2002f;51(50):1135–6. Centers for Disease Control and Prevention (CDC). Epidemic/Epizootic West Nile Virus in the United States: Guidelines for Surveillance, Prevention, and Control. Fort Collins, Colorado: Division of VectorBorne Infectious Diseases; 2003 [3rd revision]. Jia XY, Briese T, Jordan I, et al. Genetic analysis of West Nile New York 1999 encephalitis virus. Lancet 1999;354:1971–2. John TR, Nash D, Maldin B, et al. Persistence of virus-reactive serum immunoglobulin m antibody in confirmed West Nile virus Encephalitis cases. EID 2003;9(3):376–9. Kapoor, H., Manning, S.D., Clark, P., et al., 2003. Laboratory evaluation of a West Nile virus (WNV) outbreak in Michigan. Abstracted in 19th Annual Clinical Virology Symposium and Annual Meeting Pan American Society for Clinical Virology, T 51. Lanciotti RS, Roehrig JT, Deubel V, et al. Origin of the West Nile virus responsible for an outbreak of encephalitis in the northeastern United States. Science 1999;286:2333. Lanciotti RS. Rapid detection of West Nile Virus from human clinical specimens, field-collected mosquitos, and avian samples by a TaqMan reverse transcriptase-PCR assay. J Clin Microbiol 2000;38:4066–71. Martin DA, Muth DA, Brown T, et al. Standardization of immunoglobulin M capture enzyme-linked immunosorbent assays for routine diagnosis of arboviral infections. J Clin Microbiol 2000;38:1823–6. Martin DA, Biggerstaff BJ, Allen B, et al. Use of immunoglobulin M cross-reactions in differential diagnosis of human flaviviral encephalitis infections in the United States. Clin Diagn Lab Immunol 2002;9:544–9. Nash D, Mostashari F, Fine A, et al. The outbreak of West Nile Virus infection in the New York City area in 1999 2001;344:1807–14. Pealer LN, Martin AA, Petersen LR, et al. Transmission of West Nile Virus through blood transfusuion in the United States in 2002 2003;349:1236–45. Petersen LR, Roehrig JT. West Nile virus: a reemerging global pathogen. EID 2001;7:611–4. Poland JD, Calisher CH, Monath WG, et al. Persistence of neutralizing antibody 30–35 years after immunization with 17D yellow fever vaccine. Bull WHO 1981;59:895–900. Tardei G, Ruta S, Chitu V, et al. Evaluation of immunoglobulin M (IgM) and IgG enzyme immunoassays in serologic diagnosis of West Nile virus infection. J Clin Microbiol 2000;38:2232–9.