Associations between meteorological parameters and influenza activity in a Sub-tropical country: Case of five sentinel sites in Yaoundé-Cameroon

CaHReF 20116, Yaoundé Conges hall, 23 – 26 August 2016 , PL057

Influenza is associated with highly contagious respiratory infections. In countries with temperate climates, a clear seasonal peak in influenza activity occurs during the winter months, whereas in countries with tropical or subtropical climates, influenza seasonality is more variable. Meteorological factors may therefore influence how easily infection may take place.

This study aimed to determine the relationship between incidence of influenza and three meteorological parameters.

This was a retrospective and descriptive study performed in Yaoundé from January 2009 to November 2015. Weekly numbers of confirmed influenza cases from five sentinel sites in Yaoundé were considered as dependent variables, whereas, weekly values of mean temperature, average relative humidity, and accumulated rainfall were considered as independent variables. A time-series method was applied to investigate associations between influenza and weather variability. The data was divided into 2 parts; the first 71 months was used to calibrate the model, and the last 12 months to test for prediction.

Overall, there were 1173 confirmed infections with influenza virus. Univariate analysis showed that influenza transmission was favoured by cold, rainfall and high relative humidity although the relationships were weak (0.8 < IRR > 1.1). Mean temperature was the best predictor of an increase in the number of influenza cases; every 1°C drop in temperature is accompanied by a 12.8% rise in the number of influenza cases. Three prediction models were obtained for the different viral types. All models fitted well during the estimation period; however, they did not succeed to make good forecasts for predictions.

There is heterogeneity of patterns in the circulation of influenza in Cameroon. The meteorological variables considered in this study certainly acted as proxies to other factors not considered. Future studies taking into consideration other environmental factors, host-specific factors as well as socio-economic elements are warranted.

Influenza, Meteorological variables, Tropics, Cameroon