A nurse from Washington's Life Care Center in Kirkland noticed something unusual among the elderly COVID-19 patients: they all had red eyes.
Doctors in China have reported similar instances, consistent with the nurse's account. Soon, health experts connected the dots, suggesting that the new coronavirus may cause a highly contagious eye infection called pink eye, also known as conjunctivitis.
"From what we understand from a few case reports, conjunctivitis may be a presenting sign of COVID-19 infection," Drs Gerami Seitzman and Thuy Doan from the University of California, San Francisco, told MEA WorldWide (MEAWW).
This raises a question of whether the new coronavirus spreads through secretions -- such as tears -- from an infected eye.
What is a pink eye?
Pink eye is an infection or swelling of a part of the eye called the conjunctiva, a thin transparent layer of tissue that covers the white part of the eye and the inside of the eyelid. People with the condition tend to experience excessive tearing, itching or burning, blurred vision and the appearance of red or "pink" in the whites of the eye. It is not uncommon to find pus, mucus and a yellow discharge leaking out of the eye.
"It's moist and nice and hospitable for viruses there are lots of organisms that can stick very readily to your conjunctiva, or for that matter, stick on a contact lens that is also resting on your conjunctiva," Dr Thomas Steinemann, a clinical spokesperson for the American Academy of Ophthalmology, told CNN.
What does the evidence say?
Researchers are trying to figure out whether the virus can spread through contact with tears of an infected person. "The data we currently have now is limited. Information is changing very quickly as new data are published," explain Seitzman and Doan. Based on the available data, the risk of infection from someone without the pink eye is low, they add.
A Chinese study found traces of the virus in the tears of an infected patient having the pink eye. Of the 30 patients, only one patient developed the condition. They did not find traces of the virus in patients who did not develop the pink eye.
The earlier study was too small to conclude. Another study conducted by the American Academy of Ophthalmology did not find traces of the virus in the tears of infected patients. But there is a catch: none of these patients had the pink eye.
These experts believe that the pink eye among infected patients occurs in just 1% to 3% of patients, suggesting the risk of the virus spreading through tears is low.
A more recent study that investigated the link between the new coronavirus and the pink eye paints a clearer picture. Among the 38 positive Chinese patients evaluated in China, 12 experienced eye abnormalities similar to the pink eye. They saw these abnormalities in patients diagnosed with a severe form of COVID-19, consistent with the Kirkland nurse's observation.
The study also found minute traces of the virus in the tears of infected patients. Despite that, they think, the virus can spread via the eyes.
"We do not have enough data to comment on the risk of infection from an inflamed eye, though limited case reports indicate there may be an active virus," explain Drs Gerami Seitzman and Thuy Doan.
While the evidence is still scant, Dr Alfred Sommer, from Johns Hopkins Bloomberg School of Public Health, wrote a commentary wondering if China's revered hero, Dr Li Wenliang, an ophthalmologist caring for patients in Wuhan, died after coming into contact with an infected eye.
Because affected patients frequently visit eye clinics or emergency departments, ophthalmologists like Dr Li are more likely to contract the infection. "The greatest risk of transmission to ophthalmologists remains via aerosol transmission and close-contact physical examinations should proceed with caution," says Seitzman and Doan.
Dr Sommer wrote: "He earned the ire of the Chinese government for alerting the public and calling for action. He died at age 34 years from the disease. We do not know whether he became infected from contact with patients’ eyes."