Even Without Symptoms, Wuhan Coronavirus May Spread, Experts Fear

Before he became ill, he had met in Munich on Jan. 20 and Jan. 21 with a Chinese business partner. A resident of Shanghai, she had been in Germany from Jan. 19 to Jan. 22. The report said that she was healthy during her stay but got sick during her flight back to China. She tested positive for infection with the Wuhan coronavirus on Jan. 26.

Chinese authorities alerted German health officials, and the businessman was tested and found positive for the infection. On Jan. 28, three additional employees of the German company tested positive for the coronavirus. Two of them had not had any contact with the woman from Shanghai.

All of the infected were admitted to the hospital, where they were isolated and monitored. None developed severe disease.

The authors of the report, researchers in Munich and Berlin, said it was “notable that the infection appears to have been transmitted during the incubation period” of the virus. The woman suffered only a brief, mild illness and recovered.

Dr. Michael Hoelscher, one of the authors, told Science magazine that he and his colleagues had not interviewed the Chinese woman who had been ill, and relied on the accounts given by her German colleagues, who said she did not appear to have had any symptoms. Dr. Hoelscher could not be reached for comment.

Researchers from the Robert Koch Institute and the Health and Food Safety Authority of Bavaria did interview the woman on the phone, Ms. Degen said, which is how they learned that she might have had symptoms.

Julia Morin, a spokeswoman for the New England Journal of Medicine, said, “All we can say right now is that we are looking into the matter.”

Knvul Sheikh contributed reporting.