THREAD: I finally found the study I had read a while back and wished I had saved. This study was over an 8 yr period in MI. It followed several families and 4 HCoVs during that time. Children weren’t always the index cases. 1/
academic.oup.com/jid/article/22…
academic.oup.com/jid/article/22…
Let’s look at the study and some of the conclusions. “993 HCoV infections were identified during the 8 years, with OC43 most commonly seen and 229E the least.” 2/
“From 2010–11 through 2015–16, eligible households were those with 4 or more members at least 2 of whom were younger than 18 yrs. In subsequent yes, eligible households contained 3 or more members including at least 1 child younger than 5 yrs (2015-16) or <10 yrs (2017–18).” 3/
They, “defined household index cases as the first person in a household to develop ARI with HCoV detection. Secondary cases were defined as those who developed ARI with HCoV detection within 14 days following illness in a household contact with the same type.” 4/
HCoV 229E, HKU1, NL63, and OC43 were all identified using PCR testing. 5/
“Incidence per 100 person-years of human coronavirus (HCoV) infections by type over 8 study years: Household Influenza Vaccine Evaluation Study 2010–2018. Error bars represent 95% confidence intervals.” 6/ 
“Infection rates for common respiratory pathogens are highest in young children and usually fall off with increasing age. With the exception of 229E” (more on that later) 7/
“229E was associated with significantly higher odds of severe illness (versus mild) compared to the 3 other HCoV types” 8/
“Consistent with overall patterns of incidence by age, index cases were most frequently children, with the exception of 229E where adults aged 18 to 49 years were responsible for nearly half of the household introductions.” 9/
So we know that 229E was the most likely to cause severe illness and was also more likely to be spread by adults as the index cases than children, it may be possible that as different CoVs have more severity in symptoms that children become less likely the index cases. 10/end
@threadreaderapp unroll please
