Commuters wear face masks as they travel on a MTR train in Hong Kong on Feb 4, 2020. (ANTHONY WALLACE / AFP)

HONG KONG - Hong Kong's medical authorities reported one more case of infection from a novel coronavirus involving a 25-year-old man - the city's youngest patient so far. This takes to 18 the number of confirmed cases so far in Hong Kong up to 8 pm on Tuesday, the day the city reported its first fatality from the virus.

The Centre for Health Protection (CHP) of the Department of Health (DH) said early Wednesday that it was investigating the three latest cases of novel coronavirus infection, including that of the young man, as local infection cases.

Also on Wednesday, an 80-year-old passenger from Hong Kong was found to be infected with the pneumonia-causing virus on a cruise ship, the Diamond Princess, which has been kept in quarantine off the port of Yokohama, a city south of Tokyo. The infected passenger from Hong Kong flew to Tokyo in mid-January and boarded the cruise ship in Yokohama on Jan 20, Xinhua reports from Tokyo.

In Hong Kong, all three patients confirmed as infected had no history of travel during the incubation period. "According to our preliminary epidemiological investigations, the three additional confirmed cases will be classified as local infection cases," a spokesman for the CHP said.

The 25-year-old patient, a resident of Ma Tau Wai Road, To Kwa Wan, was reportedly healthy before getting infected. He developed fever on Jan 28 and sought medical help for cough, runny nose and diarrhoea on Jan 29 and attended Hong Kong Baptist Hospital on the same day. 

According to information shared by the patient, he didn't travel during the incubation period

He sought treatment at Hong Kong Baptist Hospital on Feb 3 and was referred to the Prince of Wales Hospital where he was admitted and subsequently tested positive for novel coronavirus. He is now in a stable condition.

According to information shared by the patient, he didn't travel during the incubation period. His wife is asymptomatic and will be sent to a quarantine centre.

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The taxi driver who ferried the patient from Hong Kong Baptist Hospital to Prince of Wales Hospital around 2 pm on Feb 3 has been urged to call a hotline at 2125 1122 set up by the CHP.

The CHP will report the cases to the World Health Organization, National Health Commission, Health Commission of Guangdong Province and Health Bureau of Macao.

On Tuesday, Chuang Shuk-kwan, head of the Communicable Disease Branch of the Centre for Health Protection of the Department of Health, said the recent cases - wherein patients have no recent travel history - pointed at possible community transmission and did not rule out the possibility of mass infection in Hong Kong.

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Beginning Wednesday, the DH will implement further port health measures, according to a press release issued by the government early Wednesday. Travellers departing from Kai Tak Cruise Terminal and Ocean Terminal will be required to undergo temperature checks. The health declaration arrangements for inbound travellers will also be expanded to the above two terminals, the Hong Kong Port of the Hong Kong-Zhuhai-Macao Bridge as well as drivers of cross-boundary goods vehicles of Lok Ma Chau, Man Kam To and Sha Tau Kok Control Points.