Dr. Sopon Iamsirithaworn, director of the communicable diseases division at Thailand’s Ministry of Public Health, said the woman had not visited the Wuhan seafood market, and had come down with a fever on Jan. 5. However, the doctor said, the woman had visited a different, smaller market in Wuhan, in which live and freshly slaughtered animals were also sold.

The woman is in good health now, according to Dr. Suthat Chottanapund, a senior official in the disease control department of Thailand’s Public Health Ministry. But, he said, the health authorities were waiting for laboratory results to confirm that the woman is free of the coronavirus before discharging her. She said that she wanted to do some sightseeing after she leaves the hospital, he said.

The revelation that neither the patient in Japan nor the first one found in Thailand had visited the Huanan Seafood Market, to which most of the cases have been linked, is a troubling sign that the outbreak could be spreading in Wuhan. The market was shut down and disinfected on Jan. 1, but new cases have appeared since, suggesting the virus has not been eradicated.

Concerns have grown across the region since the Chinese health authorities announced the discovery of the mysterious new virus, which has sickened dozens of people in Wuhan with pneumonialike symptoms. The city’s health commission said on Wednesday that the risk of human-to-human transmission is low but possible. Officials also said they detected the first cluster of the virus involving members of a single family.

The new virus has stirred memories in China of the 2003 outbreak of severe acute respiratory syndrome, or SARS. That virus, which is believed to have jumped to humans from animals at markets, originated in China and killed more than 800 people worldwide in 2002 and 2003. At the time, the Chinese government tried to cover up the problem, resulting in a backlash among its people. While flu experts have said the Chinese government is trying to be more transparent now, many in China are skeptical.

The local authorities in Wuhan and the W.H.O. have reiterated for weeks that no cases of human-to-human transmission have been confirmed.

Last week, researchers in China said they had “initially identified” a new coronavirus as the pathogen behind the mysterious respiratory illness. Of the 40 cases diagnosed in Wuhan, the majority of patients are middle-age and older men, the city’s health commission said on Wednesday. Five people are in critical condition, officials said.