Excretion dynamics of Henipa-related viruses in the Egyptian Rousette bat and triggers for potential spillover

(Uploaded by Plazi for the Bat Literature Project) Purpose: Influenza affects about 10% of the population every year. In the temperate zone, influenza has a unique seasonal pattern with some variations, however, the factors affecting its seasonality and variations are still unclear. This study aimed to explore the effects of El Nino and La Nina events on the timing of influenza peak activity in both western and eastern side of the Pacific Ocean; Korea and the USA. Methods & Materials: The weekly influenza surveillance data of Korea and the USA from September 2005 to July 2018 were taken from WHO FluNET site. The El Nino southern oscillation (ENSO) were retrieved from Korean Meteorological Administration. We used the definition of El Nino as the positive sea surface temperature anomalies (≥0.5 ◦C), while La Nina events are negative anomalies (≤-0.5 ◦C) of 3 months moving average. The weeks with the highest activities of influenza A and B in each season were identified and compared according to the presence of the anomalies. The pandemic season of 2009/2010 was excluded from the analysis. We used the mid-p exact test for statistical significance. Results: From 2005 to July 2018, there were 3 El Nino events and 5 La Nina events by the ENSO. The influenza A peak activity in study periods showed at 4.6(±4.2) and 3.6(±4.6) epidemic week in Korea and USA, respectively. However, in the season of La Nina, the peak activities of influenza A observed at 0.8(±1.4) and 5.6(±3.9) epidemic week in Korea and USA, respectively. The La Nina was associated with the early annual peak in Korea (p = 0.045, mid-p exact test) and the El Nino was associated delayed the annual peak in USA (p = 0.09, mid-p exact test). The peak activity of influenza B showed no statistical association with ENSO in both countries. Conclusion: Both El Nino and La Nina affect the timing of influenza A peak activity, but the direction may be the opposite across the Pacific Ocean: ENSO associated the early emergency of