Dödligt virus från Kina orsakar panik (SARS-CoV-2, COVID-19)

Increased or prolonged exposure to the virus may lead to more severe disease. That could be why doctors and health care professionals may be at a higher risk than the rest of us.
Late last month, when the virus had infected 80,000 worldwide, the Los Angles Times reported that 3,387 health workers in China had contracted COVID-19. Among the first health care professionals to die were two doctors, just 29 and 34 years old.

As a whole, doctors and nurses are more exposed to the coronavirus just by nature of working with the ill. But research also suggests that how much virus they’re exposed to matters, too. As Anna Yeung-Cheung, a virologist at Manhattanville College, told Slate‘s Shannon Palus in February, the reason a young doctor died of COVID-19 is, in part, because he was a doctor. “It’s a dosage thing,” she said.

While this hasn’t been tested in human trials for obvious ethical reasons, we do have some information about how other coronaviruses affect animals: Researchers have found the more of a virus the animal is exposed to, the worse disease it develops. “When we infect animals with related coronaviruses with a lower dose of viral particles, they don’t become as ill as if we infect them with a higher dose of viral particles,” Graham says. “So there is a dose-dependent response to illness.” The animal models are “a pretty good indicator,” she says, of why health professionals who work directly with infected people are experiencing more severe illness.

that you could catch coronavirus twice in one season, at present it appears unlikely.

https://www.aljazeera.com/indepth/features/doctor-note-herd-immunity-solve-coronavirus-200324152419919.html