Four types of human coronaviruses (OC43, 229E, HKU1 and NL63) are highly seasonal and appear to transmit similarly to influenza A (H3N2) in the same population, according to a study from the University of Michigan School of Public Health. The study authors say it’s not possible to tell whether SARS-CoV-2, a novel coronavirus which causes the COVID-19 disease, will behave likewise, but hope their findings will help scientists better prepare for what’s to come during the COVID-19 pandemic. The study was published in Journal of Infectious Diseases.
The structure of a coronavirus. Image credit: Scientificanimations.com / CC BY-SA 4.0.
“Even though the seasonal coronaviruses found in Michigan are related to the SARS-CoV-2 virus, we do not know whether that virus will behave in the future the way these seasonal viruses behave,” said Professor Arnold Monto, lead author of the study.
“Only time will tell if SARS-CoV-2 will become a continuing presence in the respiratory infection landscape, continue with limited circulation as with MERS, or like SARS, disappear from humans altogether.”
Professor Monto and his colleagues used data from the Household Influenza Vaccine Evaluation (HIVE) study, an ongoing longitudinal investigation of respiratory illnesses in households with children in the Ann Arbor area, Michigan.
For the last 10 years, between 890 to 1,441 individuals from hundreds of households participated in the study.
The study is now tracking the occurrence of SARS-CoV-2 and its potential involvement in Michigan households.
In 2010, it began tracking the occurrence of four types of human coronaviruses.
Professor Monto and co-authors looked at frequency, seasonality and household transmission characteristics of the 993 infections caused by these coronaviruses and found:
(i) when year-round surveillance was in place, most coronaviruses cases were detected between December and April/May, and peaked in January/February; only 2.5% of the cases occurred between June and September;
(ii) highest infection frequency was in children under 5 years of age;
(iii) of the 993 infections, 260 were acquired from an infected household contact;
(iv) serial intervals between index and household-acquired cases ranged from 3.2 to 3.6 days; secondary infection risk ranged from 7.2% to 12.6% by type;
(v) overall, 9% of adult cases and 20% of cases in children were associated with doctor visits; on average, 30% of influenza cases required a doctor visit;
(vi) illnesses in children less than 5 years old and those over 50 years of age were more likely to be classified as severe.
The common coronavirus strains studied are sharply seasonal in Michigan and appear, based on serial interval and secondary infection risk, to have similar transmission potential to H3N2 in the same population.
“The results are not necessarily indicative of how the novel SARS-CoV-2 coronavirus will behave,” the researchers said.
In a separate ongoing study, they are using the samples collected before the SARS-CoV-2 pandemic emerged to look at community introduction of that virus.
Preliminary results show no evidence that the novel coronavirus was present in the community before March.
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Arnold S. Monto et al. Coronavirus occurrence and transmission over 8 years in the HIVE cohort of households in Michigan. Journal of Infectious Diseases, published online April 4, 2020; doi: 10.1093/infdis/jiaa161
