Seasonality of Common Human Coronaviruses, United States, 2014-20211

Abstract

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 annual 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 COVID-19 mitigation efforts. Better definitions of HCoV seasonality can be used for clinical preparedness and for determining expected patterns of emerging coronaviruses.

Keywords: 2019 novel coronavirus disease; COVID-19; SARS-CoV-2; United States; alphacoronavirus; betacoronavirus; coronavirus; coronavirus disease; respiratory infections; seasonality; seasons; severe acute respiratory syndrome coronavirus 2; viruses; zoonoses.

Figure 1

Total tests and percentage positivity of 4 common HCoVs from weekly aggregated data submitted to the National Respiratory and Enteric Virus Surveillance System, United States, July 2014–November 2021. A) Total specimens tested for all 4 HCoV types. B) Percentage positivity of the 4 HCoV types by week. C) Percentage positivity of the common alphacoronaviruses. D) Percentage positivity of the common betacoronaviruses. HCoVs, human coronaviruses.

Figure 2

Total number of detections of the 4 common HCoVs, by week and season, from weekly aggregated data submitted to the National Respiratory and Enteric Virus Surveillance System, United States, July 2014–July 2020. The 3 vertical dotted lines, left to right, indicate the week of season onset, peak, and offset for all types combined (black line). These seasonal inflections were defined by using the retrospective slope 10 method, which uses a centered 5-week moving average of weekly detections with normalization to peak. The type-specific curves depict the actual number of detections; the black curve depicts specimens with any HCoV detections normalized to a peak of 1,000. HCoVs, human coronaviruses.

Figure 3

Percentage positivity and seasonal characteristics of common HCoVs, by season, from weekly aggregated data submitted to the National Respiratory and Enteric Virus Surveillance System, United States, October 2014–September 2021. Gray vertical lines indicate the mean starting week dates for season onset, peak, and offset for all seasons except 2020–21, based on the retrospective slope 10 method, which uses a centered 5-week moving average of weekly detections with normalization to peak to define seasonal inflections. The average onset week for the 6 seasons spanning 2014–2020 is MMWR week 44, average peak week is MMWR week 4, and the average offset week is MMWR week 19. For the 2020–21 season, the onset week is January 23 (MMWR week 3) and the peak week is May 22 (MMWR week 20) (not shown). HCoVs, human coronaviruses.