The Diamond Princess was placed in quarantine for two weeks upon arriving in Yokohama, south of Tokyo, on Feb. 3, after a man who disembarked in Hong Kong was diagnosed with the virus.

The epidemic originated in mainland China, where more than 1,100 people have now died of the virus.

About 3,700 people are on board the ship, which usually has a crew of 1,100 and a passenger capacity of 2,670.

Japan's health ministry said tests were being conducted for others deemed to need them and it would announce the results later.

The British-flagged Diamond Princess is managed by Princess Cruise Lines, one of the world's largest cruise lines and a unit of Carnival Corp.

Kyodo news agency, citing the health ministry, said that of the 39 cases, 10 were crew and 29 were passengers.

Ten were Japanese nationals and the others were from 11 countries, including the United States and China. Four were in serious condition, Health Minister Katsunobu Kato said.

People who test positive for the virus are taken off the ship to a hospital.

The quarantine officer who was infected had been handing out questionnaires checking the health of passengers and crew since Feb. 3, and had been following rules that require the wearing of a mask and gloves but not a full protective suit, according to the Nikkei business daily, quoting the health ministry.

High Risk

A health ministry official had no immediate comment, but Nikkei said the ministry was checking the officer's contacts with colleagues and family members.

Mark Kortepeter, a professor of epidemiology at the University of Nebraska Medical Center, said that although it was hard to reach conclusions based on limited information, the ship infections pointed to an "agent that is highly transmissible," at least in enclosed environments.

"The infected quarantine officer probably indicates the high risk, even for individuals who are trying to protect themselves, because the virus is unforgiving and there is no room for error in use of personal protective equipment and hand hygiene," he said. "A small number of virus particles is likely needed to infect, making it an efficient spreader."

From carmakers to airlines and hotels, the impact of the disease is punishing firms globally, including in Japan.

S&P Global Ratings said the outbreak would likely cause "damage" to the operating performances of Japanese companies in the first half, especially automobile manufacturers that are likely to face a prolonged halt in plant operations in China.

"The impact might be harsh on Nissan Motor and Honda Motor," the rating agency said in a note.

The government was considering allowing the elderly and those with chronic illnesses to disembark from the Diamond Princess before the Feb. 19 target date for the end of quarantine, some media reported.

About 80% of the passengers were aged 60 or over, with 215 in their 80s and 11 in the 90s, the English-language Japan Times newspaper reported.

Japan has sent four chartered flights to China's Hubei province, the epicenter of the outbreak, for its citizens there to return, and plans a fifth. The people who returned on the first flight will be released on Wednesday if they test negative for the virus, government officials said on Wednesday.

REUTERS