Genetics play role in effects of COVID-19
It is among the lingering mysteries of COVID-19: Why do some people catch it while others – sometimes even sleeping in the same bed – escape without symptoms?
Some factors have long been clear: Older adults are more likely to fall seriously ill, particularly if they smoke, are obese or have diabetes. People never exposed to the coronavirus won’t get sick, and exposure to a high concentration poses a higher risk for infection. The virus itself matters, too. The delta variant seems to be more contagious than earlier ones.
Even two people who look the same on paper can have a different reaction to COVID-19. Young, previously healthy people have died or been seriously disabled; 90-year-olds in cancer treatment have survived infection. The explanation, a study published Thursday suggests, may lie in their genetics.
“The human genome, and not only the viral genome, matters,” Andrea Ganna, one of the lead authors of the study, said Wednesday at a news conference.
In younger people, less likely to have health problems that put them at higher risk, genetics may play an even bigger role, said Ganna, a group leader at the Finnish Institute for Molecular Medicine and an instructor at Harvard Medical School and Massachusetts General Hospital.
The study, led by the COVID-19 Host Genomics Initiative, confirms or newly identifies 13 genes that appear to play a role in susceptibility to infection or that affect the severity of illness. One gene is involved in the response to respiratory infections. Others have no obvious explanation. Blood type affects 9% to 12% of disease susceptibility, but researchers said they could not explain why. Of two people with the same exposure to the virus, the one with Type O blood will have slightly lower risk of getting infected. Yet blood type appeared to have no effect on severity of disease.
To be teased out is the cause and effect, said Dr. Michael Murray, a professor of genetics and director for Clinical Operations in the Center for Genomic Health at the Yale School of Medicine, who was not involved in the study. High body mass index might be a risk factor for COVID-19 because being severely overweight may make it harder to clear a virus, or the genetics contributing to weight gain may be the same genes contributing to more significant illness, he said.
These genetic effects have about as much influence on susceptibility and seriousness of infection as the effect of obesity or diabetes, said Benjamin Neale, a statistical geneticist at the Broad Institute of Harvard and MIT.
“DNA isn’t destiny but it can load the dice,” his colleague Hamdi Mbarek, director of the Qatar Genome Program, which participated in the research, said via email. “This study is a big step towards understanding how many people may be playing with loaded dice when it comes to getting severely ill – or even having ‘long COVID’ – from the Delta variant, and future variants of the virus.”
The study involved 50,000 patients across 25 countries. “It’s really very important to conduct these studies on a worldwide level, because that increases our chance of making the broadest and most general discoveries,” said Mark Daly, another lead author, who directs the Finnish Institute for Molecular Medicine at the University of Helsinki and is a professor of genetics at Harvard Medical School.
The data set has been expanded to include 125,000 people who had confirmed cases. The more information researchers have, the more precisely they can identify which genes are involved in making people more susceptible to COVID-19 and more likely to end up hospitalized. Diversity is crucial, the researchers said.
“COVID-19 isn’t going away,” Mbarek said. “This is the biggest single genetic study in history of how people with slightly different DNA respond very differently to a virus. And because for the first time a study like this has involved genetic data from all parts of the world, that data will be more powerful in spotting the right genes to help develop treatments for severe COVID or long COVID.” Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The foundation does not provide editorial input.