The International Olympic Committee (IOC) insists Tokyo 2020 will go ahead despite the Wuhan coronavirus epidemic which is ravaging neighbouring China.
Many national and international sports tournaments in China have been cancelled or postponed as the death toll from the outbreak has risen above 1,000.
The Chinese Formula 1 Grand Prix in Shanghai in April is also under threat.
The Director General of the World Health Organization Tedros Adhanom Ghebreyesus said coronavirus posed a "very grave threat for the rest of the world” as he appealed on Tuesday, February 11, for more research into a possible vaccine.
"With 99 percent of cases in China, this remains very much an emergency for that country, but one that holds a very grave threat for the rest of the world," said Mr Ghebreyesus.
An IOC spokesman said: “Countermeasures against infectious diseases constitute an important part of Tokyo 2020’s plans to host a safe and secure Games.”
He said the organisers of Tokyo 2020 would continue to work with the WHO and the Japanese and Chinese governments and would review any countermeasures that might be necessary.
"We have full confidence that the relevant authorities, in particular in Japan, China and the WHO, will take all the necessary measures to address the situation," added the IOC spokesman.
The opening ceremony of the Tokyo Games is on 24 July and if it does go ahead it is possible Chinese athletes will be forbidden from taking part.
The Japanese government would have to grant them visas to enter the country and that is unlikely if coronavirus is still spreading and no vaccine has been created.
China was third on the medals table at the 2016 Olympics in Rio de Janeiro, with 70 medals, including 26 golds.
— #TokyoOlympics (@NBCOlympics) February 9, 2020
Among those hoping to retain their Olympic gold medal in Tokyo are the Chinese women’s volleyball team, the men’s and women’s table tennis squad and swimmer Sun Yang, who won the men’s 400m freestyle in Rio.
China is also dominant in weightlifting and diving and its gymnasts are always challenging for medals.
— GB Basketball (@gbbasketball) January 27, 2020
The Olympics has never faced a threat like this before.
Previously it has only been hit by political boycotts - in 1980 the US team stayed away from the Moscow Games after the Soviet Union invaded Afghanistan and four years later Soviet and Warsaw Pact athletes boycotted the Los Angeles Games.
— Joe Calleri (@JDC9876) February 8, 2020
The coronavirus is thought to have been transmitted to humans from animals, possibly bats, and the virus is passed on by inhaling microbes due to coughing or sneezing.
The WHO has declared an international emergency and so far it has spread to more than 20 other countries, including Japan, Russia, Britain, the US, France, Spain, Singapore and India.
A cruiseliner, the Diamond Princess, has been quarantined in the Japanese port of Yokohama after stopping in Hong Kong - 135 passengers and crew on board have tested positive for the virus.
There are around 3,700 people on board the ship.
