Of the patients who have died in mainland China, more than 80 percent were older than 60, and more than 75 percent had an underlying health condition that put them at greater risk, Jiao Yahui, an official with China’s health commission, said on Tuesday. Two-thirds of the fatalities were men, she added.

The death in Hong Kong came as the city entered the second day of a strike by hospital workers demanding that the government close the border with mainland China. Many countries have shut off or sharply curtailed traffic to and from China to prevent the virus from spreading.

The patient had traveled to Wuhan by train on Jan. 21, and had returned to Hong Kong two days later, the Hong Kong government said in a statement. Health officials said he also had diabetes, which can impair the immune system.

His death raised further concerns in the city because of the possibility that the disease was transmitted within the man’s household. His mother, who did not travel to Wuhan, later contracted the virus. The man’s wife and two children and a domestic helper who worked for him are being quarantined.

Hong Kong has 17 confirmed cases of the new strain of coronavirus, including four that are highly likely to have been transmitted locally, said Chuang Shuk-kwan, a health department official.

Dr. Chuang said there was a “significant risk of community transmission in Hong Kong” and a large-scale local outbreak could not be ruled out.