STAT reports:

Her husband collapsed just before reaching the top of the stairs in their small one-bedroom house in São Paulo, Brazil. Frantic, Thais Andrade grabbed the portable pulse oximeter she had purchased after hearing that a low oxygen reading could be the first sign of the novel coronavirus. Erik’s reading was hovering eight points lower than it had that morning. He also looked feverish.

“When he hit 90% [on the oximeter], I said we can’t wait anymore,” Andrade recalled. “I called an ambulance.”

At the hospital that day in June 2020, a CT scan showed multiple lesions in her husband’s lungs — an indication of severe Covid-19 infection – which was later confirmed via a blood test. Erik, 44, had likely contracted the virus up to a week earlier, from a friend who had visited their home.

He spent the next several weeks on oxygen in the ICU, a stay that was complicated by blood clots before he was discharged. But it wasn’t his sudden decline and subsequent recovery that is notable: It’s that Andrade had been sharing the same close quarters with her husband while he was infected and able to transmit the virus. She never wore a mask in the home with him. They shared the same bed. They were physically intimate. Yet when tested for an active or past infection — twice — her bloodwork came up negative.

And that wasn’t the only time she was potentially exposed. As part of her research work as a veterinary neurologist, she went to a meeting at the University of São Paulo where an infected attendee set off a chain reaction of positivity – but Andrade dodged it. Her tests were again negative.

Both experiences suggest that Andrade may have won a sort of biological lottery — that she’s one of a lucky few “resistant” to the virus that has killed more than 4 million people. But how? That’s the mystery researchers around the world have set out to unravel. [Continue reading…]