Another 99 people have tested positive for coronavirus onboard the stricken Princess Diamond cruise ship docked in Japan, bringing the total number of confirmed infections to 454.

Meanwhile concern is growing over possible infections among passengers from another cruise liner that docked in Cambodia last week. On Sunday a traveller from the MS Westerdam was confirmed to have the virus in Malaysia, days after disembarking along with hundreds of other passengers.

It is not clear how many travellers remain in Cambodia and how many have already travelled on to further destinations. The Cambodian health ministry did not respond to requests for comment.

The cruise operator, Holland America Line, told Reuters that guests who had left Cambodia would be “contacted by their local health department and be provided further information”. It is not clear if passengers will be asked to self-isolate once they return home.

Hundreds of American passengers from the Diamond Princess, where travellers have been mostly confined to their cabins since 3 February, have been flown back to the US. Fourteen passengers tested positive during the evacuation, the US state department said.

Australia said it would follow suit on Wednesday. Both countries have said citizens will face a further two weeks of quarantine after arriving home. Forty American passengers who were diagnosed with the virus have already been transferred to hospitals in Japan.

Some Diamond Princess passengers still on the ship face another two weeks in isolation if they have shared a cabin with someone who tests positive.

The total number of people infected around the world climbed to more than 71,000 on Monday, including a further 2,048 confirmed cases in China, where the total number of deaths stands at 1,770. Five people have died outside China. Of the 105 deaths reported in China on Monday, 100 were in Hubei province, the centre of the outbreak.

Cities in Hubei have stepped up measures to stop the virus’s spread. The city of Xiaogan – which has a population of nearly 5 million people and the second highest number of confirmed cases in China – ordered residents to stay in their homes or face detention of up to 10 days. China also said it may postpone its annual congress in March – its biggest political meeting of the year – because of the outbreak.

Facebook Twitter Pinterest Image from a video taken on 17 February shows American passengers who were evacuated from the Diamond Princess cruise ship on a plane bound for the US. Photograph: AP

Japanese public health experts advising the government defended the decision to isolate passengers and crew on the Diamond Princess.

“Many people are testing positive on the ship, but that is because we are testing everyone onboard, regardless of their medical condition,” said Shigeru Omi, the chief director of the Japan Community Health Care Organisation. “And 70% of those testing positive are not showing any symptoms at all.”

With fresh cases emerging daily, the Japanese government has advised citizens to avoid mass gatherings. On Monday it cancelled celebrations for the emperor’s birthday, while organisers of the Tokyo marathon cancelled next month’s mass participation race, in which 38,000 people were due to take part.

Omi said any disruption to this summer’s Tokyo Olympics – including possible cancellation of the Games – would depend on how and if the virus mutates in the coming months, as well as the effectiveness of the international community’s attempts to contain the outbreak.

“Whether the virus is under control by the time of the Olympics is anyone’s guess,” he said at a media briefing in Tokyo.

Omi conceded that tracing the chain of domestic transmissions not related to the Diamond Princes was proving difficult, but denied that Japan, which has confirmed 65 cases on land, was becoming a second major infection cluster.

“Our focus now is on community-based preventive action to lower the speed of the transmission of the virus,” he said. “It is true that there have been silent transmissions, but Japan is certainly not in a state of pandemic.”

Q&A How can I protect myself and others from the coronavirus outbreak? Show Hide The World Health Organization is recommending that people take simple precautions to reduce exposure to and transmission of the coronavirus, for which there is no specific cure or vaccine. The UN agency advises people to: Frequently wash their hands with an alcohol-based hand rub or warm water and soap

Cover their mouth and nose with a flexed elbow or tissue when sneezing or coughing

Avoid close contact with anyone who has a fever or cough

Seek early medical help if they have a fever, cough and difficulty breathing, and share their travel history with healthcare providers

Advice about face masks varies. Wearing them while out and about may offer some protection against both spreading and catching the virus via coughs and sneezes, but it is not a cast-iron guarantee of protection Many countries are now enforcing or recommending curfews or lockdowns. Check with your local authorities for up-to-date information about the situation in your area. In the UK, NHS advice is that anyone with symptoms should stay at home for at least 7 days. If you live with other people, they should stay at home for at least 14 days, to avoid spreading the infection outside the home.

A hospital near Tokyo said it was no longer accepting new patients because one of its nurses had tested positive for the virus after treating an infected patient who later died.

A member of the diagnosis team from Japan’s health ministry also tested positive for the disease, the ministry said. The virus’s spread in Japan has prompted calls for the government to speed up testing and offer clearer advice on when to seek medical help.

Analysts warned of potentially “huge” damage to Japan’s economy, saying the widening fallout from the virus was damaging output and tourism, undermining growth and risking pushing the country into recession.

Facebook Twitter Pinterest Medical team members from Chongqing prepare to travel to Xiaogan in Hubei, the latest city to order residents to stay in their homes or face detention of up to 10 days. Photograph: Chine Nouvelle/SIPA/REX/Shutterstock

There is concern, too, over the growing number of reported cases in Japan involving people who have not visited China recently or knowingly had direct contact with people arriving from the country.

“We agreed that the present situation represents the early stage of a domestic outbreak. This could progress further,” said Takaji Wakita, the chief of the National Institute of Infectious Diseases, after the first meeting of a taskforce at the prime minister’s office.

Pressure on Japan’s health services increased again on Monday with the arrival in Tokyo of a government-chartered flight carrying 65 Japanese nationals from Wuhan, bringing the total number repatriated from the Chinese city to 763.

Japan’s health minister, Katsunobu Kato, urged the public to avoid crowds and “non-essential gatherings”, including notoriously packed commuter trains, and said the country was “entering a new phase” in the outbreak of the virus.

Koji Wada, a professor of public health at the International University of Health and Welfare, told the Asahi Shimbun: “There is the possibility that the infection may have spread to people well beyond the groups of patients who have been identified.”

The government has made extra funds available for emergency countermeasures it says will be in place by the end of March.

Employers in Japan are also starting to feel the effects of the outbreak. On Monday, Nippon Telegraph and Telephone, one of the country’s biggest firms, said it was urging its 200,000 group employees to work from home or stagger their commutes.

Agencies contributed to this report