I am operating when it arrives. Between patients I read the email hastily. It concerns an article from surgeons at Stanford University. Along with colleagues in the United States, Italy, China, and Iran, they are reporting an increased risk of death from COVID-19 among otolaryngologists, neurosurgeons – and ophthalmologists, like me. Surgery around the nasal passages or other mucous membranes of the face seems to release a potentially lethal aerosolised load of the SARS-CoV-2 virus. Among the casualties are surgeons in their 30s.

Even as the number of new coronavirus cases falls and the country tentatively starts lifting restrictions it's easy to think that the danger is passing. But for frontline medics the danger of contracting the disease is ever present; one in 10 COVID cases has no known contact history and many people have few or no symptoms.