Finding the onset of COVID-19 - a correlation analysis with influenza epidemic around the world

Abstract

Background. COVID-19 showed similar and overlapping symptoms compared with seasonal influenza. It is difficult to distinguish them, especially in the early stage of the outbreak. The confluence of the two diseases might result in considerable morbidity, it is doubtful that whether COVID-19 had already affected the morbidity of influenza earlier than the first report.Methods. We conducted Kolmogorov-Smirnov Test and Kruskal Wallis Test to discover seasonal and regional distributions of influenza and COVID-19. Cluster analysis was utilized to explore possible influence factors. Spearman Test was carried out for analyzing correlations between the two diseases. We employed Arima Model to predict time series of WMI. We proved differences between the forecasted and the original time series of influenza from 2019 to 2021 by Mann-Whitney U Test. Then we observed first abnormal peaks on the time series, tracing back to the onset of COVID-19 affecting influenza compared with the first-report time.Results. WMI and WMC varied significantly in four seasons, five continents and the ten selected countries. Cluster analysis divided the data into two groups according to country, continent, population and morbidity. WMI of China, Israel, Honduras, Morocco and Nigeria were correlated with WMC. The forecasted and the original time series of influenza from 2019 to 2021 were significantly different. Compared with the forecasted one, some abnormal peaks firstly appeared on the original time series of influenza around Dec.31st, 2018 on Austria, Norway, Morocco and Nigeria, Jan.28th, 2019 on South Africa, Apr.8th, 2019 on Marshall Islands, Jul.7th, 2019 on America, Sep.30th, 2019 on China and Israel, Mar.11th, 2020 on Honduras.Conclusions. Winter and autumn were the high incidence season for influenza and COVID-19, respectively. Oceania and Americas owned the highest incidence rate for these two diseases. Human immunity, continents, countries’ policies and population were possible influence factors. Only in Honduras, the first reported COVID-19 case happened concurrently with the abnormal value of the ILI. And in the rest of the included countries, COVID-19 might happen earlier than its first reports. Among these regions, COVID-19 might firstly affect Africa in the first week of 2019.