Li Wenliang, the doctor in China who raised early awareness of the new coronavirus, died of the virus in February at 34. His death was shocking not only because of his role in publicizing the developing epidemic but also — given that young people do not have a high risk of dying from Covid-19 — because of his age.

Is it possible that Dr. Li died because as a doctor who spent a lot of time around severely ill Covid-19 patients, he was infected with such a high dose? After all, though he was one of the first young health care workers to die after being exposed up close and frequently to the virus, he was unfortunately not the last.

The importance of viral dose is being overlooked in discussions of the coronavirus. As with any other poison, viruses are usually more dangerous in larger amounts. Small initial exposures tend to lead to mild or asymptomatic infections, while larger doses can be lethal.