Identical twins who both came down with COVID-19 are giving researchers some insight into how genetics might influence the severity of disease, the New York Times reports.
It adds that twins like Kimberly and Kelly Standard had differing disease courses, with Kimberly spending a month in the hospital in critical condition, while Kelly spent less than a week there. But twins Krista Burkett and Kasey Miller had the same symptoms, just a week apart, the Times adds.
It notes that researchers in the US, Australia, and Europe have been using twin registries to confirm that genetics can affect COVID-19 symptoms. One study has suggested that genetic factors might account for about half the differences in symptoms, it says.
But, the Times adds that these analyses have found that the environment and chance also play a role. While identical twins have similar genomes, differences do arise and twins' immune systems, which are shaped by their environmental exposures, can differ, the Times notes.
"It would be wrong to think we can answer this if we just crack the genes," Tim Spector, the director of the TwinsUK registry, tells the Times.