The new strain of coronavirus, in the same family as the deadly severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), originated in Wuhan, the largest city in central China, and has spread to Thailand via a Chinese tourist.
However, he said mainland doctors believed the three men were most likely to have been exposed to the same virus in the market.
Recently, officials reported the first "exported" case of the virus in Thailand.
The World Health Organization (WHO) is warning hospitals around the world of a new virus identified in China.
Sars is a type of coronavirus that first struck southern China in late 2002. Preliminary investigations indicate that most patients who've contracted the virus had contact with the market, though a woman may have contracted the virus from her husband, who worked at the market, the Wuhan Municipal Health Commission said in a public notice. Hong Kong health official Chuang Shuk-kwan said that it's also possible that the man brought food home from the market that infected his wife.
Wuhan's health commission said on Wednesday that most of the patients diagnosed with the virus were male, and many were middle-aged or elderly.
Wuhan health authorities said on Wednesday that the patients also include a husband and his wife.
Thai health officials are stepping up monitoring and inspection at its airports for the new mystery virus from China ahead of Lunar New Year, when Chinese visitors flock to the Southeast Asian country, a health official said on Wednesday.
A vendor gives out copies of newspaper with a headlines of "Wuhan break out a new type of coronavirus, Hong Kong prevent SARS repeat" at a street in Hong Kong, Saturday, Jan. 11, 2020.
In Hong Kong, hospitals have raised their alert level to "serious" and stepped up detection measures including temperature checkpoints for inbound travellers. It said the woman had been isolated and was in a stable condition, while those who had close contact with her were under medical observation.
She said the organisation was preparing for the possibility of a wider outbreak.
On Monday, a 61-year-old Wuhan woman was quarantined after landing in Bangkok as she was diagnosed with a pneumonia-like virus.
"From the information that we have it is possible that there is limited human-to-human transmission", Maria Van Kerkhove, acting head of WHO's emerging diseases unit, told reporters in Geneva.