TY - JOUR
T1 - Nonannual seasonality of influenza-like illness in a tropical urban setting
AU - Lam, Ha Minh
AU - Wesolowski, Amy
AU - Hung, Nguyen Thanh
AU - Nguyen, Tran Dang
AU - Nhat, Nguyen Thi Duy
AU - Todd, Stacy
AU - Vinh, Dao Nguyen
AU - Vy, Nguyen Ha Thao
AU - Thao, Tran Thi Nhu
AU - Thanh, Nguyen Thi Le
AU - Tin, Phan Tri
AU - Minh, Ngo Ngoc Quang
AU - Bryant, Juliet E.
AU - Buckee, Caroline O.
AU - Ngoc, Tran Van
AU - Chau, Nguyen Van Vinh
AU - Thwaites, Guy E.
AU - Farrar, Jeremy
AU - Tam, Dong Thi Hoai
AU - Vinh, Ha
AU - Boni, Maciej F.
N1 - Publisher Copyright:
© 2018 The Authors. Influenza and Other Respiratory Viruses Published by John Wiley & Sons Ltd.
PY - 2018/11
Y1 - 2018/11
N2 - Background: In temperate and subtropical climates, respiratory diseases exhibit seasonal peaks in winter. In the tropics, with no winter, peak timings are irregular. Methods: To obtain a detailed picture of influenza-like illness (ILI) patterns in the tropics, we established an mHealth study in community clinics in Ho Chi Minh City (HCMC). During 2009-2015, clinics reported daily case numbers via SMS, with a subset performing molecular diagnostics for influenza virus. This real-time epidemiology network absorbs 6000 ILI reports annually, one or two orders of magnitude more than typical surveillance systems. A real-time online ILI indicator was developed to inform clinicians of the daily ILI activity in HCMC. Results: From August 2009 to December 2015, 63 clinics were enrolled and 36 920 SMS reports were received, covering approximately 1.7M outpatient visits. Approximately 10.6% of outpatients met the ILI case definition. ILI activity in HCMC exhibited strong nonannual dynamics with a dominant periodicity of 206 days. This was confirmed by time series decomposition, stepwise regression, and a forecasting exercise showing that median forecasting errors are 30%-40% lower when using a 206-day cycle. In ILI patients from whom nasopharyngeal swabs were taken, 31.2% were positive for influenza. There was no correlation between the ILI time series and the time series of influenza, influenza A, or influenza B (all P > 0.15). Conclusion: This suggests, for the first time, that a nonannual cycle may be an essential driver of respiratory disease dynamics in the tropics. An immunological interference hypothesis is discussed as a potential underlying mechanism.
AB - Background: In temperate and subtropical climates, respiratory diseases exhibit seasonal peaks in winter. In the tropics, with no winter, peak timings are irregular. Methods: To obtain a detailed picture of influenza-like illness (ILI) patterns in the tropics, we established an mHealth study in community clinics in Ho Chi Minh City (HCMC). During 2009-2015, clinics reported daily case numbers via SMS, with a subset performing molecular diagnostics for influenza virus. This real-time epidemiology network absorbs 6000 ILI reports annually, one or two orders of magnitude more than typical surveillance systems. A real-time online ILI indicator was developed to inform clinicians of the daily ILI activity in HCMC. Results: From August 2009 to December 2015, 63 clinics were enrolled and 36 920 SMS reports were received, covering approximately 1.7M outpatient visits. Approximately 10.6% of outpatients met the ILI case definition. ILI activity in HCMC exhibited strong nonannual dynamics with a dominant periodicity of 206 days. This was confirmed by time series decomposition, stepwise regression, and a forecasting exercise showing that median forecasting errors are 30%-40% lower when using a 206-day cycle. In ILI patients from whom nasopharyngeal swabs were taken, 31.2% were positive for influenza. There was no correlation between the ILI time series and the time series of influenza, influenza A, or influenza B (all P > 0.15). Conclusion: This suggests, for the first time, that a nonannual cycle may be an essential driver of respiratory disease dynamics in the tropics. An immunological interference hypothesis is discussed as a potential underlying mechanism.
UR - http://www.scopus.com/inward/record.url?scp=85052486358&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85052486358&partnerID=8YFLogxK
U2 - 10.1111/irv.12595
DO - 10.1111/irv.12595
M3 - Article
C2 - 30044029
AN - SCOPUS:85052486358
SN - 1750-2640
VL - 12
SP - 742
EP - 754
JO - Influenza and other Respiratory Viruses
JF - Influenza and other Respiratory Viruses
IS - 6
ER -