Share prices were on track for the worst week since the global financial crisis in 2008 as virus-related disruptions to international travel and supply chains fuelled fears of recession in the United States and the Euro zone.

Asian stocks tracked a plunge on Wall Street, where the benchmark S&P 500 index fell more than four per cent on Thursday.

Mainland China - where the virus originated late last year - reported 327 new cases, the lowest since January 23, taking its tally to more than 78,800 cases with almost 2800 deaths.

Four more countries reported first cases taking the number of countries and territories outside China with infections to 55, with about 3700 cases killing about 70 people.

Countries other than China are accounting for about three-quarters of new infections.

An Italian man who arrived in Nigeria this week was confirmed as the first coronavirus case in Africa's most populous country. And a person who returned on a flight from Iran became the first in New Zealand.

While in eastern Europe, Belarus and Lithuania both reported their first cases.

Mongolia, which has yet to confirm a case, placed its president, Battulga Khaltmaa, in quarantine after he returned from a trip to China as a precaution.

Scientists warn that much remains unknown about the virus, which can lead to pneumonia, and say a vaccine could take up to 18 months to develop.

A Chinese health official said some recovered patients had been found to be infectious, raising fears the epidemic may be even harder to eradicate.

In addition to stockpiling medical supplies, governments ordered schools shut and cancelled big gatherings to try to halt the flu-like disease known as COVID-19.

US President Donald Trump's administration was considering invoking special powers to expand production of protective gear, two officials told Reuters.

In Europe, France's number of reported cases doubled, Germany warned of an impending epidemic and Greece, a gateway for refugees from the Middle East, announced tighter border controls.

The death toll in Italy, Europe's worst-hit country, rose to 17 and the number of people who tested positive for the illness increased by more than 200 to 655.

Germany has about 45 cases, France about 38 and Spain 23, according to a Reuters count.

Tedros told reporters in Geneva that Iran, Italy and South Korea were at a "decisive point" in their efforts to prevent a wider outbreak.

South Korea has the most cases outside China, and reported 256 new infections on Friday, bringing the total to 2022.

Japan is scheduled to host the 2020 Olympics in July but discussions were being held with organisers about whether to go ahead.

As of Friday, confirmed cases in Japan topped 200, with four deaths, excluding more than 700 cases and four more deaths from a quarantined cruise liner, Diamond Princess.

Japan has told schools to close and said big gatherings should be scrapped or curtailed, while pledging the Games would go ahead.

Australian Associated Press