Coronavirus can be caught from the eyes and tears of some infected patients, a team of doctors in China reported Tuesday in JAMA Ophthamology, a monthly medical journal.

The purpose of the research was to investigate whether coronavirus manifested in the eyes in people who developed COVID-19. For this purpose, Dr. Ping Wu of the Yichang Central People’s Hospital and colleagues report in JAMA how they checked for ocular manifestations and symptoms in the conjunctiva (the inner tissue of the eyelids and the tissue covering the white of the eyes) in COVID-19 patients treated between February 9 to 15 at a hospital center in Hubei province, where the virus first arose.

It is true that their study was a very small one, involving just 38 patients, but the results were striking. Only two yielded positive findings for the virus causing the disease, SARS-CoV-2, in their conjunctiva – but a third of the group, 12 patients, had developed conjunctivitis eye infection.

Open gallery view Medical workers who volunteered in Wuhan to help combat the COVID-19 outbreak before they board a bus to return home, in Wuhan, China, on March 31, 2020. Credit: NOEL CELIS / AFP

Among these 12 patients, four were in moderate condition, two were in severe condition and six were judged to be critical. The more severe their condition, the more likely they were to develop the associated eye infection, the doctors report. Commensurately, the research found discovered that the COVID-19 patients with conjunctivitis had higher white blood cells counts than patients without ocular manifestations.

In one case, the patient experienced watery eyes and conjunctivitis as the first symptom of infection with coronavirus. None experienced blurred vision, the doctors add.

The previous attack of a novel coronavirus, due the quickly contained SARS epidemic (caused by SARS-CoV-1), did not produce evidence that SARS-CoV-1 replication results in conjunctivitis or other eye disease. But then and now, the conventional wisdom in medical circles had been that the eye was a potential site for virus transmission, and now it seems to have been proven.

The doctors conclude that COVID-19 patients who develop severe pulmonary conditions will commonly also have ocular symptoms.

Although COVID-19 first broke out in November or December last year, much remains unknown about the disease, including its mortality rate. The virus in question was a new one to humans, and is believed to have begun in a so-called “wet market” in Hubei where wild animals were sold for human consumption. Speculation about the source of the virus and any intermediate host between that source and people has focused on bats, snakes and pangolins, aka scaly anteaters, both of which are considered to be delicacies in the East. But the true source remains unknown.

The course of the new disease and its mortality rates also remain unclear. Dr. Alfred Sommer of the John Hopkins Bloomberg School of Public Health points out in JAMA on Tuesday that the influenza that caused the 1918 pandemic, which killed somewhere from 20 to 50 million people worldwide, primarily afflicted the young and robust. This one seems to affect primarily the weaker population, from the elderly to the immune-impaired to smokers. Estimates of the mortality rate of COVID-19 range enormously, from about 1 per cent to 5 per cent, but we won’t actually know until the dust settles.

But meanwhile a vast body of work being done around the world on the strange new virus is growing, and now we know that SARS-Cov-2 can invade the conjunctiva, that the virus can be found in patients’ tears; and that the eyes can serve as a source of its spread. This is crucial information for medical teams, the people helping and transporting people suspected to have caught COVID-19, and families alike.

It bears adding one thing. Dr. Sommer points out that the earliest cries of alarm about COVID-19 were made by Dr LiWenliang of Wuhan, who died of the disease at age 34. He was an ophthalmologist. Now we know he might have caught coronavirus from a patient’s eyes.