The secret to why some people get so sick from covid could lie in their genes

Some people die from covid-19, and others who are infected don't even show symptoms. But scientists still don't know why.

Now consumer genomics company 23andMe is going to offer free genetic tests to 10,000 people who've been hospitalized with the disease, hoping to turn up genetic factors that could point to an answer.

While it's known that older people and those with health conditions such as diabetes are most at risk, there could be hidden genetic reasons why some young, previously healthy people are also dying.

23andMe operates a large gene database with more than 8 million customers, many of whom have agreed to let their data be used for research. The company has previously used consumer data to power searches for the genetic roots of insomnia, homosexuality, and other traits.

In April the company, based in Sunnyvale, California, sent covid-19 questionnaires out to a swath of its members. So far, says a company spokesman, about 400,000 have enrolled, including 6,000 who say they have confirmed cases of the pandemic disease.

The 23andMe gene hunt will complement efforts from university researchers to obtain genetic profiles of covid-19 cases and pair them with detailed medical records, says Andrea Ganna, who coordinates the Covid-19 Host Genetic Initiative. The international consortium is sharing genetic data on covid-19 cases from Italy, the UK, and the US and regularly making results public.

Scientists hope to find a gene that strongly influences, or even determines, how badly people are affected by the coronavirus. There are well-known examples of such genetic effects on other diseases: for example, sickle-cell genes confer resistance to malaria, and variants of other genes are known to protect people from HIV or to norovirus, an intestinal germ.

According to Ganna, however, an initial peek at the genes of 900 covid-19 cases turned up no significant genetic hits. His consortium is now preparing an analysis of twice as many cases, which could improve their chance of spotting an association.

If we don't find a really big signal in the next month or so, then I think genetics is not going to be of huge value in the management of the disease, like determining who you treat," he says. What is still very, very important is the biology, and understanding the biology through the genetics, and then with vaccination."

In its first survey, 23andMe asked customers if they'd been diagnosed with covid-19 or not. However, the company is now trying to locate patients who were hospitalized and recovered, because their genes are more likely to hold important information.

Researchers have already speculated that blood type could influence a person's version of ACE-2, the protein the coronavirus uses to fuse with human cells and gain access to them. But preliminary findings have not yet been borne out by the larger gene hunts.

The gene search is part of the scientific effort to move to more targeted ways of managing the pandemic, which some are calling precision epidemiology." In addition to 23ndMe, the DNA testing company Ancestry said it had received 250,000 responses in its own covid-19 project.