Seasonality of Common Human Coronaviruses in the United States, 2014-2021

The four common human coronaviruses (HCoVs), including two alpha (HCoV-NL63 and HCoV-229E) and two beta (HCoV-HKU1 and HCoV-OC43) types, generally cause mild, upper respiratory illness. HCoVs are known to have seasonal patterns and variation in predominant types each year, but defined measures of seasonality are needed. We defined seasonality of HCoVs during July 2014 to November 2021 in the United States using a retrospective method applied to National Respiratory and Enteric Virus Surveillance System (NREVSS) data. In the six HCoV seasons prior to 2020-2021, onsets ranged from October to November, peaks from January to February, and offsets from April to June; most (>93%) HCoV detections occurred within the defined seasonal onsets and offsets. The 2020-2021 HCoV season onset was delayed by 11 weeks compared to prior seasons, likely due to COVID-19 mitigation efforts. Better defining HCoV seasonality can inform clinical preparedness and the expected patterns of emerging HCoVs.Article Summary LineThe typical common HCoV season in the United States starts between October and November, peaks towards the end of January, and ends between April and June, but the 2020-2021 season was markedly delayed compared to prior seasons.