Doctors began seeing people with symptons including fever, cough and breathing difficulties, in people who worked at or visited the market late last month.
The new cases suggest that the illness, which has killed two people and sickened at least 62 in China, is continuing to spread. During Chunyun, the period around Chinese New Year, about three billion people move around the country to return home to relatives for the celebration. "Self-sustaining human-to-human transmission should not be ruled out", it says. Three overseas infections have been reported, two in Thailand and one in Japan.
The unknown virus however is from the same large family of coronaviruses that includes Severe Acute Respiratory Syndrome (SARS), which killed almost 800 people globally during a 2002-03 outbreak that also started in China.
The US and Japan are among countries that have started screening passengers from central China, but as the lunar new year travel rush approaches, Australia is yet to begin doing so.
Wuhan's health commission also noted several epidemiologic details, including that an analysis of data of earlier cases found that some had no history of contact with the seafood market at the center of the investigation, which also sold other animals such as poultry, bats, marmots, and wild game meat.
If the reported infections are confirmed, they would be the first cases of the disease in the mainland outside Wuhan.
Health officials in the inland city announced on Sunday that they had confirmed 17 new cases of the disease.
Thailand reports second case infected with novel coronavirus
The male patient surnamed Xiong, 69, died at 0:45am on January15, said the statement by Wuhan Municipal Health Commission. While the overall risk to people in the United States is low, "we know it's crucial to be proactive and prepared", Dr.
No human-to-human transmission has been confirmed so far, but the Wuhan Municipal Health Commission has said that the possibility "cannot be excluded". Due to China's efforts to implement broader screening, new cases may be identified in the coming days and weeks, it added.
"Much remains to be understood about the new coronavirus", it said.
The true scale of a viral pneumonia outbreak in China is likely far bigger than officially reported, scientists have said, as countries ramp up measures to prevent the disease from spreading.
Most cases have been linked to the Huanan Seafood Market (also known as Wuhan South China Seafood City and South China Seafood Wholesale Market), which was closed as of January 1 for cleaning and disinfection.
A State Department spokesman said the United States was closely monitoring the outbreak in China as well as actively working with governments across the region to combat spread of the virus.
News about the outbreak was trending on Weibo, a microblogging platform in China, on Sunday morning.