Demographic science aids in understanding the spread and fatality rates of COVID-19

Jennifer Beam Dowd; Valentina Rotondi; Liliana Adriano; David M Brazel; Per Block; Xuejie Ding; Yan Liu; Melinda C Mills

Age structure, along with early detection and treatment, also likely explains the low numbers of fatalities in South Korea and Singapore compared to Italy. The Korean outbreak, while large, was concentrated amongst the young recruits of the Shincheonji religious group (6) , with only 3.3% of cases falling into the very vulnerable >80 group.(7) Singapore is notable with zero deaths thus far, but have had only one confirmed case over 80 and only 10/200 cases above age 70. (8) COVID-19 transmission chains that begin in younger populations may have a low number of severe cases and thus go longer undetected, (9, 10) with countries thereby slow to raise the alarm. The low case fatality rate in England thus far may reflect the relatively young age structure of populations impacted to date, including Greater London, which has a small fraction of residents over age 65 compared to more rural areas (11). COVID-19 was only detected in King County, Washington once it reached the Life Care Centre in Kirkland, where 19 out of 22 deaths occurred, despite estimates based on virus genetic sequences suggesting it circulated for several weeks prior (12). Once community transmission is established, countries that have a high level of intergenerational contacts and co-residence may see faster transmission to high-fatality age groups as seen in Italy.