Seasonality will ‘eventually’ play a role in COVID-19 transmission
A study examining the epidemiology of seasonal coronaviruses and other respiratory viruses showed that SARS-CoV-2 will likely form seasonal winter patterns of infection eventually but not immediately.
“The virus that causes COVID-19, SARS-CoV-2, is currently invading a new niche, the human respiratory tract, which is already occupied by many respiratory pathogens, including several coronaviruses,” Sema Nickbakhsh, PhD, research associate at the MRC University of Glasgow Centre for Virus Research at the Institute of Infection, Immunity and Inflammation, told Healio. “These common coronaviruses typically cause cold symptoms but can also lead to more severe illness requiring hospitalization.”
Nickbahksh and colleagues examined routine diagnostic data on more than 70,000 episodes of respiratory illness that were tested molecularly for multiple respiratory viruses between 2005 and 2017. The aim of their study was to understand the spread of common coronaviruses and determine which people are at risk for illness in order to better understand the ways that SARS-CoV-2 may establish itself in humans.
There were 84,957 episodes of respiratory illness during the study period. The prevalence of seasonal coronavirus (sCoV) overall was 4% among tested patients (2,958 of 74,519), contributing to 10.7% of all respiratory virus detected. The most common viruses detected during influenza seasons among virus-positive patients included human rhinoviruses (15.3% to 46.2%), influenza viruses (13.4% to 34%, excluding pandemic influenza waves in the 2009-2010 and 2010-2011 seasons) and respiratory syncytial virus (10.1% to 21.9%), followed by sCoVs (7.7% to 17.4%).
The number of sCoVs detected increased before pandemic influenza (March 2011 to September 2017) and the overall number of sCoV detections went from 545 before to 2,072 after the pandemic influenza period, although a drop in prevalence among the patients tested was observed, with varying patterns at the individual sCoV level.
According to Nickbahksh, the study showed that there are differences in regard to the timing of spread and the age groups affected when comparing coronavirus species. In addition, coronavirus species that are more genetically related show differences in terms of the timing and magnitude of their spread and the age groups they affect.
“It is likely that SARS-CoV-2 will form seasonal winter patterns of infection in temperate regions in the long term. It is possible that, during these seasons, it will be in competition with two particular species of common coronaviruses that it is more closely related to,” she added. “Seasonality will likely play a role in the transmission of COVID-19 eventually — but not immediately.”
Nickbakhsh also noted that tracking SARS-CoV-2 infections in the health care setting is going to be important in the long term to determine whether the virus establishes in the human population, and if it does, what it means for the overall and comparative burdens of viral respiratory infections in different health care settings.
“For example, SARS-CoV-2 may cause a shift in age groups admitted to the hospital and those needing intensive care if it displaces other coronaviruses or acts cooperatively with others,” she said. “A greater understanding of the role of coinfections with other respiratory viruses in relation to the susceptibility to, and severity of, SARS-CoV-2 infection is needed.” – by Caitlyn Stulpin
Disclosure: The authors report no relevant financial disclosures.