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

The 4 common types of human coronaviruses (HCoVs)-2 alpha (HCoV-NL63 and HCoV-229E) and 2 beta (HCoV-HKU1 and HCoV-OC43)-generally cause mild upper respiratory illness. Seasonal patterns and an-nual variation in predominant types of HCoVs are known, but parameters of expected seasonality have not been defined. We defined seasonality of HCoVs during July 2014-November 2021 in the United States by using a retrospective method applied to National Respiratory and Enteric Virus Surveillance System data. In the 6 HCoV seasons before 2020-21, season onsets occurred October 21-November 12, peaks January 6-February 13, and offsets April 18-June 27; most (>93%) HCoV detection was within the defined seasonal onsets and offsets. The 2020-21 HCoV season onset was 11 weeks later than in prior seasons, probably associated with CO-VID-19 mitigation efforts. Better definitions of HCoV sea-sonality can be used for clinical preparedness and for de-termining expected patterns of emerging coronaviruses.

Automated summary

This study defined the seasonality of human coronaviruses in the United States by analyzing the data from the National Respiratory and Enteric Virus Surveillance System. The findings showed a regular pattern of season onset, peak, and offset for human coronaviruses in the previous seasons. However, the onset of the 2020-21 season was delayed by 11 weeks, possibly due to the mitigation efforts for COVID-19.