Researchers Establish Characteristics of 7 Common Coronaviruses

With the coronavirus disease 2019 (COVID-19) pandemic bringing new attention to the family of coronaviruses, researchers from the University of Michigan (UM) have defined the clinical characteristics of all 7 coronaviruses known to infect humans.¹

Of the 7 viruses, 4 cause common respiratory infections, according to the authors. Notably, all coronaviruses are very seasonal and appear to transmit similarly to influenza. While the authors of the study, published in the Journal of Infectious Diseases, said it is not yet clear whether COVID-19 will behave in the same ways, they hope their research could help public health officials prepare for the future of the pandemic.¹

The study began tracking the occurrence of 4 kinds of human coronaviruses (OC43, 229E, HKU1, and NL63) in 2010. They identified 993 infections caused by these coronaviruses, and analyzed the frequency, seasonality, and household transmission characteristics.¹

The authors analyzed data from the Household Influenza Vaccine Evaluation Study, an ongoing longitudinal study of respiratory illnesses in households with children in the Ann Arbor, Michigan, area. Between 890 and 1441 individuals have participated in the study, and it is now tracking the novel coronavirus and its potential effects in the area.¹

The results found that when year-round surveillance was in place, only 2.5% of the coronaviruses cases occurred between June and September, while the vast majority were detected between December and April/May. The viruses peaked in January and February.¹

The highest infection frequency was seen in children ages 5 years and younger, and 20% of pediatric cases were associated with physician visits. Just 9% of adult cases of coronavirus were associated with doctor visits, compared to an average of 30% of influenza cases. Illnesses in children younger than 5 years and in adults over age 50 years were more likely to be classified as severe. Notably, of the 993 infections, 260 were acquired from an infected household contact.¹

Although these findings suggest that most coronaviruses ebb as the weather gets warmer, experts have also noted that the COVID-19 pandemic is unlikely to slow as summer approaches. Even if warmer weather was damaging to the COVID-19 virus, the lack of host immunity would likely counteract those effects.²

“Given that countries currently in ‘summer’ climates, such as Australia and Iran, are experiencing rapid virus spread, a decrease in cases with increases in humidity and temperatures elsewhere should not be assumed,” a group of researchers said in a paper published by the National Academy of Sciences, Engineering, and Medicine.²

The investigators from the University of Michigan emphasized that COVID-19 may not necessarily behave like other coronaviruses and influenza outbreaks.¹

“Only time will tell if [severe acute respiratory syndrome-coronavirus-2] will become a continuing presence in the respiratory infection landscape, continue with limited circulation as with [Middle East respiratory syndrome], or like [severe acute respiratory syndrome], disappear from humans altogether,” said Arnold Monto, the Thomas Francis Collegiate Professor of Epidemiology at the UM School of Public Health, in a statement.¹

REFERENCES

• Common coronaviruses are highly seasonal, with most cases peaking in winter months [news release]. University of Michigan; April 6, 2020. https://news.umich.edu/common-coronaviruses-are-highly-seasonal-with-most-cases-peaking-in-winter-months/. Accessed April 9, 2020.
• Van Beusekom M. Experts: COVID-19 pandemic unlikely to ebb as weather warms. Center for Infectious Disease Research and Policy; April 8, 2020. https://www.cidrap.umn.edu/news-perspective/2020/04/experts-covid-19-pandemic-unlikely-ebb-weather-warms. Accessed April 9, 2020.