This is the season when the peak of COVID-19 cases occurs

Ahead of targeted vaccination trials, virologists are hopeful that SARS-Cov-2 will evidence a similar trajectory to previously studied coronaviruses.

That hope recently became a potential reality with a new study published in the Journal of Infectious Disease.  

An in-depth analysis conducted by researchers from the University of Michigan, of coronavirus transmissions from an eight-year-long Household Influenza Vaccine Evaluation Cohort Study, revealed that the most common coronavirus strains peak in the winter months. 

As of the time of this writing, more than 1,400 individuals from over a hundred Michigan households have participated in this exhaustive review. 

The lion’s share of coronavirus cases was recorded between December and May, peaking around January or February. A modest 2.5% of cases occurred between June and September. 

This data is consistent with preceding literature suggesting that SARS-Cov-2 experiences virus inactivation as quickly as five minutes when incubation temperatures rise to 70°C.

“In total, 993 HCoV infections were identified over 8 years, with OC43 most commonly seen and 229E the least. HCoVs were detected in a limited time period, between December and April/May, and peaked in January/February,” the authors wrote in the new paper. “Coronaviruses are sharply seasonal. They appear, based on serial interval and secondary infection risk, to have similar transmission potential to influenza A(H3N2) in the same population.”

The vast majority of coronaviruses have not made the leap from animals to humans. Four of the seven that have successfully crossed the divide have demonstrated pathologies that resemble the strain staffing our current pandemic. The deadly SARS epidemic of 2002 began with a zoonotic infection and the same is true of the MERS outbreak of 2012.

Both proved to be acutely seasonal, both aggressively attacked lung cells and both enjoyed the highest transmission rates in colder climates.

In fact, SARS-Cov-2 is the most stable at 4°C. At this temperature, its fomites are even detectable after two weeks. 

Still, no COVID-19 data set should be taken as gospel. The coronavirus at hand is a mutation. Virtually every similarity it shares with other zoonotic viruses is matched by a discerning distinction; varying case severities and an inconsistent incubation cycle being chief among them. The previously studied coronaviruses also infected a large portion of small children, which is not the case for SARS-Cov-2. 

Nine percent of adult cases and 20% of child cases from The HIve report required medical intervention of some kind. Of the 993 infections reviewed, 260 occurred between members within a household as opposed to a travel cluster. The serial interval between index and household-acquired cases ranged between 3.2 to 3.6 days and the secondary infection risk ranged from 7.2% to 12.6% depending on the type. As you can see, none of these findings align with what we know about COVID-19 cases. Recently Ladders compiled all of the data linking case severity and high transmission rates.

“Even though the seasonal coronaviruses found in Michigan are related to SARS-CoV-2, we do not know whether that virus will behave like the seasonal coronaviruses,” explained Arnold Monto, the Thomas Francis Collegiate Professor of Epidemiology at Michigan’s School of Public Health, in a media release. “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.”