Seasonality of absolute humidity explains seasonality of influenza-like illness in Vietnam

Thai, Pham Quang; Choisy, Marc; Dương, Trần Như; Thiem, Vu Dinh; Yen, Nguyen Thu; Hiển, Nguyễn Trần; Weiss, Daniel J.; Boni, Maciej F.; Horby, Peter

doi:10.1016/j.epidem.2015.06.002

Cited by 74 publications

(84 citation statements)

References 36 publications

(12 reference statements)

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“…In the Philippines, there was a positive relationship between both influenza types and SH, which is consistent with data reported for tropical Vietnam [33] and South America [34]. This could be explained by the viability of influenza virus in airborne respiratory droplets [21, 30].…”

Section: Discussionsupporting

confidence: 87%

Seasonality of Influenza and Respiratory Syncytial Viruses and the Effect of Climate Factors in Subtropical–Tropical Asia Using Influenza-Like Illness Surveillance Data, 2010 –2012

et al. 2016

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IntroductionThe seasonality of influenza and respiratory syncytial virus (RSV) is well known, and many analyses have been conducted in temperate countries; however, this is still not well understood in tropical countries. Previous studies suggest that climate factors are involved in the seasonality of these viruses. However, the extent of the effect of each climate variable is yet to be defined.Materials and MethodsWe investigated the pattern of seasonality and the effect of climate variables on influenza and RSV at three sites of different latitudes: the Eastern Visayas region and Baguio City in the Philippines, and Okinawa Prefecture in Japan. Wavelet analysis and the dynamic linear regression model were applied. Climate variables used in the analysis included mean temperature, relative and specific humidity, precipitation, and number of rainy days. The Akaike Information Criterion estimated in each model was used to test the improvement of fit in comparison with the baseline model.ResultsAt all three study sites, annual seasonal peaks were observed in influenza A and RSV; peaks were unclear for influenza B. Ranges of climate variables at the two Philippine sites were narrower and mean variables were significantly different among the three sites. Whereas all climate variables except the number of rainy days improved model fit to the local trend model, their contributions were modest. Mean temperature and specific humidity were positively associated with influenza and RSV at the Philippine sites and negatively associated with influenza A in Okinawa. Precipitation also improved model fit for influenza and RSV at both Philippine sites, except for the influenza A model in the Eastern Visayas.ConclusionsAnnual seasonal peaks were observed for influenza A and RSV but were less clear for influenza B at all three study sites. Including additional data from subsequent more years would help to ascertain these findings. Annual amplitude and variation in climate variables are more important than their absolute values for determining their effect on the seasonality of influenza and RSV.

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Section: Discussionsupporting

confidence: 87%

Seasonality of Influenza and Respiratory Syncytial Viruses and the Effect of Climate Factors in Subtropical–Tropical Asia Using Influenza-Like Illness Surveillance Data, 2010 –2012

et al. 2016

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“…The lack of correlation between influenza trends and ILI trends suggests that the transmission dynamics of respiratory disease differ between tropical and temperate zones, consistent with the past decade's literature on this topic 10,11,13,17,43,46 . Given the observed pattern of multiple ILI peaks in our data, some of which are influenza epidemics and some of which are not, the natural hypothesis explaining this pattern is that multiple respiratory pathogens co-circulate and cause asynchronous epidemics.…”

Section: Discussionsupporting

confidence: 60%

“…This contrasts with the climate mechanisms proposed in temperate zones where it is postulated that the onset of abnormally low absolute humidity is closely associated with the onset of the influenza season 41 . The larger question on climate effects and influenza -why AH, RH, and temperature appear to have different transmission effects in temperate and tropical regions 11,43,59 -remains to be answered. Much work remains to be done before respiratory disease outbreaks in the tropics can be forecast accurately; our hope is that the non-annual signal identified in this study will help in this endeavor.…”

Section: Cc-by-nc-mentioning

confidence: 99%

“…In the tropics, it is not known whether influenza dynamics obey classic SIR models, whether they are characterized by low-level persistence, or a combination of the two. It is also not known which climate-influenza associations are expected to be present in tropical countries despite some recent advances on this topic 11,43 . If the intrinsic epidemiological dynamics and the presence/absence of climate associations can be understood, forecasting of influenza epidemics in the tropics may be possible.…”

Section: Introductionmentioning

confidence: 99%

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Non-annual seasonality of influenza-like illness in a tropical urban setting

Lam

Wesolowski

Hung

et al. 2017

Preprint

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In temperate countries, influenza and other viral respiratory diseases often have distinct seasonal peaks occurring during colder, wintertime months. However, little is known about the dynamics of influenza and viral respiratory disease dynamics in the tropics, despite high morbidity and a clear epidemiological link between tropical and temperate countries. In temperate countries, the dynamics of influenza and other respiratory diseases are often analyzed using syndromic surveillance data describing influenza-like illness (ILI) as ILI is highly correlated with virological surveillance for influenza. To obtain a detailed picture of respiratory disease incidence patterns in a large tropical city, we established an mHealth study in community outpatient clinics in Ho Chi Minh City, Vietnam (11N latitude). From August 2009 through December 2015, clinics reported daily case numbers of ILI using standard mobile-phone SMS messaging. A subset of these clinics performed molecular diagnostics for influenza A and B viruses. Unlike the annual patterns seen in temperate countries, ILI activity in Ho Chi Minh City exhibited strong non-annual periodicity and was not correlated with PCR-confirmed influenza. The dominant periodicity in the data was approximately 200 days. This was confirmed by a time series decomposition, a step-wise regression analysis on annual and non-annual covariates, and a forecasting exercise showing that forecasting was 30% to 40% more accurate when a 200-day non-annual cycle was included in the forecast. This suggests, for the first-time, that a non-annual cycle may be an essential driver of ILI dynamics in the tropics. This raises new questions about the seasonality and drivers of respiratory disease transmission in tropical countries.

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“…In most studies conducted on the epidemiology of human influenza viruses, climatic factors have been mentioned as major drivers of changes in disease incidence over time 2–4 . The temporal dynamics of zoonotic influenza viruses, which are transmitted from domestic animals to humans, have been comparatively less studied than those between humans, partly because their emergence as a public health concern is relatively recent.…”

Section: Introductionmentioning

confidence: 99%

Economic factors influencing zoonotic disease dynamics: demand for poultry meat and seasonal transmission of avian influenza in Vietnam

Delabouglise

Choisy

Phan

et al. 2017

Sci Rep

Self Cite

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While climate is often presented as a key factor influencing the seasonality of diseases, the importance of anthropogenic factors is less commonly evaluated. Using a combination of methods – wavelet analysis, economic analysis, statistical and disease transmission modelling – we aimed to explore the influence of climatic and economic factors on the seasonality of H5N1 Highly Pathogenic Avian Influenza in the domestic poultry population of Vietnam. We found that while climatic variables are associated with seasonal variation in the incidence of avian influenza outbreaks in the North of the country, this is not the case in the Centre and the South. In contrast, temporal patterns of H5N1 incidence are similar across these 3 regions: periods of high H5N1 incidence coincide with Lunar New Year festival, occurring in January-February, in the 3 climatic regions for 5 out of the 8 study years. Yet, daily poultry meat consumption drastically increases during Lunar New Year festival throughout the country. To meet this rise in demand, poultry production and trade are expected to peak around the festival period, promoting viral spread, which we demonstrated using a stochastic disease transmission model. This study illustrates the way in which economic factors may influence the dynamics of livestock pathogens.

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Seasonality of absolute humidity explains seasonality of influenza-like illness in Vietnam

Cited by 74 publications

References 36 publications

Seasonality of Influenza and Respiratory Syncytial Viruses and the Effect of Climate Factors in Subtropical–Tropical Asia Using Influenza-Like Illness Surveillance Data, 2010 –2012

Seasonality of Influenza and Respiratory Syncytial Viruses and the Effect of Climate Factors in Subtropical–Tropical Asia Using Influenza-Like Illness Surveillance Data, 2010 –2012

Non-annual seasonality of influenza-like illness in a tropical urban setting

Economic factors influencing zoonotic disease dynamics: demand for poultry meat and seasonal transmission of avian influenza in Vietnam

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