The ultimate COVID-19 mystery: Why does it spare some and kill others?

LMT Online:

The novel coronavirus can be a killer – or no big deal. It can put a person in the intensive care unit on a ventilator, isolated from family, facing a lonely death – or it can come and go without leaving a mark, a ghost pathogen, more rumor than reality.

Six months into a pandemic that has killed more than 400,000 people globally, scientists are still trying to understand the wildly variable nature of covid-19, the disease caused by the virus.

Among their lines of inquiry: Are distinct strains of the coronavirus more dangerous? Does a patient’s blood type affect the severity of the illness? Do other genetic factors play a role? Are some people partially protected from covid-19 because they’ve had recent exposure to other coronaviruses?


Jean-Laurent Casanova, head of the St. Giles Laboratory of Human Genetics of Infectious Diseases at Rockefeller University, is co-leading an international team searching the genomes of “outliers” – patients younger than 50 who had no known preexisting conditions, but were hospitalized with life-threatening cases of covid-19. They’re looking for unusual gene variants that these patients have in common.


One potential breakthrough was highlighted recently: Scientists developed an artificial intelligence tool that sorted the blood of covid-19 patients and found 22 proteins that consistently appear among the patients who are severely ill.

At this point, such a blood marker only tells doctors what they can already see with their own eyes – a very sick patient. But if such a blood test and analysis could be rolled out early in the course of the disease, it could help doctors decide which patients are most vulnerable.

Blood-type research is also intriguing. This month, European scientists posted online a study – not yet peer-reviewed – that found strong links between variations on two places in the genome and respiratory failure in covid-19 patients in Italy and Spain.

One, the ABO gene, determines blood type. The researchers found that patients who had Type A blood had a 50% higher risk of needing oxygen or a ventilator. Type O blood seemed to have a partial protective effect.

The consumer genetics giants and 23andMe are getting involved. 23andMe recently released preliminary findings showing that people with Type O blood are 9 to 18% less likely to test positive for covid-19 than people with other blood types. The company is still exploring links between blood type and disease severity.


More than 750,000 of the company’s customers have completed a web-based survey about their experiences with covid-19, and 2,000 of them said they’d been hospitalized from the disease. The company is now recruiting 10,000 non-customers who have been hospitalized with covid-19.

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