The association between multiple meteorological factors and seasonal influenza A and B virus transmission in Macau

Abstract Background and objectives: Few studies evaluated the influence of meteorological factors on different influenza types activity in subtropical regions. The study aimed to explore the association between meteorological factors and the onset of influenza A (Flu-A) and B (Flu-B) in Macau.Methods: Daily influenza cases data were collected from Kiang Wu Hospital from January 1st, 2014 to December 31st, 2018 in Macau. Daily meteorological data were obtained from Macau Meteorological Service. The distributed lag non-linear model (DLNM) was used to estimate the effects of meteorological factors on the seasonal influenza outbreak.Results：Mean temperature had the peaking risks of both types at 4.0°C and 28.0°C. For the diurnal temperature range (DTR), the peaks of the cumulative relative risk (RR) of Flu-A were at 1.0°C and 5.0°C, while the cumulative RR of Flu-B increased as the DTR decreased. The association between influenza and relative humidity were showed a U-shape curve. The risk of influenza increased when the relative humidity was below 50% or above 90%. Both types increased significantly when the sunshine duration was below about 3.5 hours. Taking the median value as the reference, a significant cold effect was observed along 16-24 lag days in Flu-A. The lag effects were found in low-DTR, humid and short sunshine conditions in both types.Conclusions：This study revealed the complex non-linear association between meteorological factors and the different influenza types activity in Macau. The finding helped to develop an early warning system to improve the response capacity to influenza epidemics.