Dr. W. Ian Lipkin, an epidemiologist at Columbia University who advised the Chinese government and the World Health Organization during the SARS outbreak, said that infected people outside Wuhan would continue to spread the disease.

“The horse is already out of the barn,” he said.

An examination of the information provided by the government about the initial deaths show a disease that has thus far largely killed older men, many of who had underlying health problems.

Most had gone to the hospital with a fever and a cough, though at least three did not have fevers when they were admitted, according to the health commission’s statement.

Among the first 17 victims were 13 men and four women. All were identified only by their last names. The youngest was a 48-year-old woman, Yin, who died on Monday, more than a month after her symptoms were first recorded. The oldest cases were two 89-year-old men who died on Saturday and Sunday. The median age was 75.

Many had underlying conditions like cirrhosis of the liver, hypertension, diabetes and Parkinson’s disease. Most spent more than a week in hospitals, with some undergoing treatment for a month or longer. But two died just four days after they were admitted.

While much about the virus remains unknown, medical experts found some positive signs in the fact that the disease did not appear to be killing young and otherwise healthy people.

It was a somewhat reassuring sign, Dr. Lipkin wrote, that “the majority of fatal cases are elderly and/or have a chronic disease that would increase their susceptibility to infectious diseases.”