Global Seasonality of Human Seasonal Coronaviruses: A Clue for Postpandemic Circulating Season of Severe Acute Respiratory Syndrome Coronavirus 2?

BACKGROUND: The ongoing pandemic of coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) could recur as seasonal outbreaks, a circulating pattern observed among other preexisting human seasonal coronaviruses (sCoVs). However, little is known about seasonality of sCoVs on a global scale. METHODS: We conducted a systematic review of data on seasonality of sCoVs. We compared seasonality of sCoVs with influenza virus and respiratory syncytial virus. We modeled monthly activity of sCoVs using site-specific weather data. RESULTS: We included sCoV seasonality data in 40 sites from 21 countries. sCoVs were prevalent in winter months in most temperate sites except for China, whereas sCoVs tended to be less seasonal in China and in tropical sites. In temperate sites excluding China, 53.1% of annual sCoV cases (interquartile range [IQR], 34.6%-61.9%) occurred during influenza season and 49.6% (IQR, 30.2%-60.2%) of sCoV cases occurred during respiratory syncytial virus season. Low temperature combined with high relative humidity was associated with higher sCoV activity. CONCLUSIONS: This is the first study that provides an overview of the global seasonality of sCoVs. Our findings offer clues to the possible postpandemic circulating season of SARS-CoV-2 and add to the knowledge pool necessary for postpandemic preparedness for SARS-CoV-2.