There are some clues already. Researchers have identified an association between type O and rhesus negative blood groups, and a lower risk of severe disease. But while scientists have hypothesised that people with certain blood types may naturally have antibodies capable of recognising some aspect of the virus, the precise nature of the link remains unclear.

But Bobe is far from the only scientist attempting to tease apart what makes Covid-19 outliers unique. Mayana Zatz, director of the Human Genome Research Centre at the University of São Paulo has identified 100 couples, where one person got Covid-19 but their partner was not infected. Her team is now studying them in the hope of identifying genetic markers of resilience. “The idea is to try and find why some people who are heavily exposed to the virus do not develop Covid-19 and remain serum negative with no antibodies,” she says. “We found out that this is apparently relatively common. We received about 1,000 emails of people saying that they were in this situation.”

Zatz is also analysing the genomes of 12 centenarians who have only been mildly affected by the coronavirus, including one 114-year-old woman in Recife who she believes to be the oldest person in the world to have recovered from Covid-19. While Covid-19 has been particularly deadly to the older generations, elderly people who are remarkably resistant could offer clues for new ways to help the vulnerable survive future pandemics.