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Empirical estimation of the incubation period for hand-foot-and-mouth disease from school outbreaks
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Abstracts / International Journal of Infectious Diseases 53S (2016) 4–163
Results: A high correlation between the curves obtained by Google trend and epidemic curves Ministry of Health (febrile cases) was observed 0.89 (0.05) Pearson correlation coefficient. Starting time, duration and decline of epidemic curve are well correlated. Magnitude in terms of number of cases needs to be fitted to strong data (as confirmed cases, no available data so far). National events as Holidays (Christmas) or Political events (elections) could affect the curves related to behavioral changes search patterns, also Internet penetration in rural areas. Conclusion: The Google trend tool can be useful where epidemiological information is not available on a regular basis, has a high ability to forecast the timing of the epidemic, the relative magnitude and duration of the outbreaks, it’s free and available to all who can use the information, also can predict the shape of the outbreak in “real time” fashion which its almost impossible for regular epidemiological data that takes week/months to be available. http://dx.doi.org/10.1016/j.ijid.2016.11.329 20.107 Empirical estimation of the incubation period for hand-foot-and-mouth disease from school outbreaks Z. Yang ∗ , Q. Zhang, W. Chiu, B.J. Cowling, E.H. Lau The University of Hong Kong, School of Public Health, Hong Kong/CN Purpose: Outbreaks of hand-foot-and-mouth disease (HFMD) occurred frequently in Asia and occasionally in Europe and the US. The incubation period, defined as the time elapsed from infection to symptom onset, is important to guide disease control and prevention. The incubation period of HFMD is commonly described as 3–7 days but was supported by limited quantitative evidence. In this study we estimated the incubation period of HFMD from school outbreaks in Hong Kong. Methods & Materials: In 2015-2016, we recruited 24 kindergartens, 3 primary and 8 secondary schools which reported to have HFMD cases. We collected information on the dates of symptom onset and absence for the diagnosed HFMD cases, and potential epidemiological link to other HFMD cases in household. We extracted classes with ≥2 HFMD cases for the analysis. The distribution of incubation period was estimated allowing for interval censoring. We assumed the HFMD cases were infectious after symptom onset. For each HFMD case, the possible exposure period for other students in the same class was defined from the day of symptom onset to the school day before taking sick leave. The time differences between the exposure period to all potential infectors and the symptom onset day of the subsequent HFMD cases were used to estimate the incubation period. We fitted lognormal, gamma and Weibull distributions by maximum likelihood method and selected the best-fitted distribution by Akaike information criterion. We estimated the median, 5% and 95% percentiles and computed the relevant 95% confidence interval by bootstrap method. Results: Among the 35 schools, 105 cases from 29 classes in 19 schools were included for analysis. Weibull distribution was the best-fitted model with an estimated median incubation period of 4.5 (95% CI: 4.1-5.1) days. The estimated 5% and 95% percentiles were 0.6 and 14.3 days respectively. Conclusion: The median incubation period of HFMD is consistent to the range of 3–7 days commonly cited by different health agencies. However, the incubation period can be more variable and not uncommon to be longer than a week. The finding may have
implications on the recommendation of disease control in a school setting. http://dx.doi.org/10.1016/j.ijid.2016.11.330 20.109 Evaluation of the performance of randomly amplified polymorphic DNA (RAPD) method for microbiological typing in an invasive Serratia marcescens NICU outbreak R.M. Alyazidi a,∗ , R. Hickman b , L.M. Li c , J. Osowicki d , D. Goldfarb e , P. Tilley f , D.P. Speert g , J.E.A. Zlosnik h a
University of British Columbia and King AbdulAziz University, Division of Infectious Diseases, Department of Pediatrics, Faculty of Medicine, Vancouver/ Jeddah- Saudi Arabia/CA b Centre for Understanding and Preventing Infection in Children and the Canadian Burkholderia cepacia research and referral repository, Division of Infectious Diseases, Department of Paediatrics, Vancouver/CA c University of British Columbia, Department of Microbiology and Immunology Division of Medical Microbiology, Provincial Health Services Authority, Vancouver/CA d University of British Columbia, Division of Infectious Diseases, Department of Paediatrics, Vancouver/CA e Provincial Health Services Authority and University of British Columbia, Department of Microbiology and Immunology Division of Medical Microbiology, Vancouver/CA f Provincial Health Services Authority and University of British Columbia, Department of Microbiology and Immunology Division of Medical Microbiology, Vancouver/CA g Centre for Understanding and Preventing Infection in Children and the Canadian Burkholderia cepacia research and referral repository and University of British Columbia, Division of Infectious Diseases, Department of Paediatrics, Vancouver/CA h Univerity of British Columbia and Centre for Understanding and Preventing Infection in Children and the Canadian Burkholderia cepacia research and referral repository, Division of Infectious Diseases, Department of Paediatrics, Vancouver/CA Purpose: Serratia marcescens is a common pathogen in the hospital environment and colonizes patients. It is a serious cause of nosocomial outbreaks of invasive infections. There is limited experience using polymerase chain reaction (PCR)-based randomly amplified polymorphic DNA (RAPD) method for typing of S. marcescens isolates for timely investigation of an outbreak. We sought to evaluate the performance of PCR-RAPD method using different primer sets compared to a reference method in the context of a neonatal intensive care unit (NICU) outbreak of invasive S. marcescens. Methods & Materials: Stored isolates of S. marcescens and cluster-related patient isolates over 2 months, were sub-cultured and genomic DNA was extracted. Blinded PCR amplification of each isolate DNA was performed using 4 primer sets, 2 of which were previously published primers for fingerprinting S. marcescens and 2 RAPD primers which were tested for the first time (272 P. aeruginosa
Abstracts / International Journal of Infectious Diseases 53S (2016) 4–163
Results: A high correlation between the curves obtained by Google trend and epidemic curves Ministry of Health (febrile cases) was observed 0.89 (0.05) Pearson correlation coefficient. Starting time, duration and decline of epidemic curve are well correlated. Magnitude in terms of number of cases needs to be fitted to strong data (as confirmed cases, no available data so far). National events as Holidays (Christmas) or Political events (elections) could affect the curves related to behavioral changes search patterns, also Internet penetration in rural areas. Conclusion: The Google trend tool can be useful where epidemiological information is not available on a regular basis, has a high ability to forecast the timing of the epidemic, the relative magnitude and duration of the outbreaks, it’s free and available to all who can use the information, also can predict the shape of the outbreak in “real time” fashion which its almost impossible for regular epidemiological data that takes week/months to be available. http://dx.doi.org/10.1016/j.ijid.2016.11.329 20.107 Empirical estimation of the incubation period for hand-foot-and-mouth disease from school outbreaks Z. Yang ∗ , Q. Zhang, W. Chiu, B.J. Cowling, E.H. Lau The University of Hong Kong, School of Public Health, Hong Kong/CN Purpose: Outbreaks of hand-foot-and-mouth disease (HFMD) occurred frequently in Asia and occasionally in Europe and the US. The incubation period, defined as the time elapsed from infection to symptom onset, is important to guide disease control and prevention. The incubation period of HFMD is commonly described as 3–7 days but was supported by limited quantitative evidence. In this study we estimated the incubation period of HFMD from school outbreaks in Hong Kong. Methods & Materials: In 2015-2016, we recruited 24 kindergartens, 3 primary and 8 secondary schools which reported to have HFMD cases. We collected information on the dates of symptom onset and absence for the diagnosed HFMD cases, and potential epidemiological link to other HFMD cases in household. We extracted classes with ≥2 HFMD cases for the analysis. The distribution of incubation period was estimated allowing for interval censoring. We assumed the HFMD cases were infectious after symptom onset. For each HFMD case, the possible exposure period for other students in the same class was defined from the day of symptom onset to the school day before taking sick leave. The time differences between the exposure period to all potential infectors and the symptom onset day of the subsequent HFMD cases were used to estimate the incubation period. We fitted lognormal, gamma and Weibull distributions by maximum likelihood method and selected the best-fitted distribution by Akaike information criterion. We estimated the median, 5% and 95% percentiles and computed the relevant 95% confidence interval by bootstrap method. Results: Among the 35 schools, 105 cases from 29 classes in 19 schools were included for analysis. Weibull distribution was the best-fitted model with an estimated median incubation period of 4.5 (95% CI: 4.1-5.1) days. The estimated 5% and 95% percentiles were 0.6 and 14.3 days respectively. Conclusion: The median incubation period of HFMD is consistent to the range of 3–7 days commonly cited by different health agencies. However, the incubation period can be more variable and not uncommon to be longer than a week. The finding may have
implications on the recommendation of disease control in a school setting. http://dx.doi.org/10.1016/j.ijid.2016.11.330 20.109 Evaluation of the performance of randomly amplified polymorphic DNA (RAPD) method for microbiological typing in an invasive Serratia marcescens NICU outbreak R.M. Alyazidi a,∗ , R. Hickman b , L.M. Li c , J. Osowicki d , D. Goldfarb e , P. Tilley f , D.P. Speert g , J.E.A. Zlosnik h a
University of British Columbia and King AbdulAziz University, Division of Infectious Diseases, Department of Pediatrics, Faculty of Medicine, Vancouver/ Jeddah- Saudi Arabia/CA b Centre for Understanding and Preventing Infection in Children and the Canadian Burkholderia cepacia research and referral repository, Division of Infectious Diseases, Department of Paediatrics, Vancouver/CA c University of British Columbia, Department of Microbiology and Immunology Division of Medical Microbiology, Provincial Health Services Authority, Vancouver/CA d University of British Columbia, Division of Infectious Diseases, Department of Paediatrics, Vancouver/CA e Provincial Health Services Authority and University of British Columbia, Department of Microbiology and Immunology Division of Medical Microbiology, Vancouver/CA f Provincial Health Services Authority and University of British Columbia, Department of Microbiology and Immunology Division of Medical Microbiology, Vancouver/CA g Centre for Understanding and Preventing Infection in Children and the Canadian Burkholderia cepacia research and referral repository and University of British Columbia, Division of Infectious Diseases, Department of Paediatrics, Vancouver/CA h Univerity of British Columbia and Centre for Understanding and Preventing Infection in Children and the Canadian Burkholderia cepacia research and referral repository, Division of Infectious Diseases, Department of Paediatrics, Vancouver/CA Purpose: Serratia marcescens is a common pathogen in the hospital environment and colonizes patients. It is a serious cause of nosocomial outbreaks of invasive infections. There is limited experience using polymerase chain reaction (PCR)-based randomly amplified polymorphic DNA (RAPD) method for typing of S. marcescens isolates for timely investigation of an outbreak. We sought to evaluate the performance of PCR-RAPD method using different primer sets compared to a reference method in the context of a neonatal intensive care unit (NICU) outbreak of invasive S. marcescens. Methods & Materials: Stored isolates of S. marcescens and cluster-related patient isolates over 2 months, were sub-cultured and genomic DNA was extracted. Blinded PCR amplification of each isolate DNA was performed using 4 primer sets, 2 of which were previously published primers for fingerprinting S. marcescens and 2 RAPD primers which were tested for the first time (272 P. aeruginosa