A woman working as a tour-bus guide in Japan has tested positive for the Covid-19 coronavirus for a second time, raising fears of a "bi-phasic" infection pattern similar to anthrax.

Photo: AFP / FILE

The woman, a resident of Osaka, in western Japan, tested positive on Wednesday after developing a sore throat and chest pains, the prefectural government said in a statement, describing her as being in her forties.

She first tested positive in late January and was discharged from hospital after recovering on 1 February, according to the statement.

Japan's Health Minister Katsunobu Kato said in parliament the central government would need to review patient lists and keep tabs on the condition of those previously discharged, as health experts analysed the implications of testing positive for the virus after an initial recovery.

NYU School of Medicine professor of microbiology and pathology Philip Tierno Jr said much remained unknown about the virus, and it was possible the disease was bi-phasic, meaning symptoms could go away before returning again later on.

"Once you have the infection, it could remain dormant and with minimal symptoms, and then you can get an exacerbation if it finds its way into the lungs," Prof Tierno said.

"I'm not certain that this is not bi-phasic, like anthrax."

The second positive test came as the number of confirmed cases in Japan rose to 186 by Thursday, from about 170 the day before.

Tokyo has urged big gatherings and sports events be scrapped or curtailed for two weeks to contain the virus while pledging the 2020 Olympic Games will still go ahead in the city.

NZ reviews Japan travel advice

Meanwhile, New Zealand's Ministry of Foreign Affairs and Trade announced today it had reviewed its travel advice for Japan because of the virus.

"We now advise that New Zealanders exercise increased caution elsewhere in Japan due to the outbreak of Covid-19 (coronavirus) and associated health risks," a statement said.

The ministry maintained its other advice against travel near the Fukushima Dai-ichi nuclear power plant.

Read more about the Covid-19 coronavirus:

Global Covid-19 coronavirus situation

The number of new Covid-19 coronavirus infections inside China - the source of the outbreak - has for the first time been overtaken by fresh cases elsewhere.

Italy has reported more than 400 cases, centered on the industrial heartlands of Lombardy and Veneto.

While Iran has reported only 139 cases, epidemiologists said the death rate of around 2 percent seen elsewhere and reported deaths of 19 suggested the true number of cases must be many times higher.

China's outbreak appeared to be declining, with officials saying the number of new deaths stood at 29 on Thursday, the lowest daily rate since 28 January.

The virus has now killed a total of 2744 people in the country, mostly in the central province of Hubei.

The US Centers for Disease Control and Prevention on Wednesday warned of the possibility of a community spread of the coronavirus in the country after a person in California who reportedly did not have relevant travel history or exposure to another known patient was infected.

Dozens of people were being checked for the virus in the New York City area on Wednesday, officials said, but Governor Andrew Cuomo said the state has had no confirmed cases so far.

US health authorities have already said a global pandemic is likely. US President Donald Trump today announced Vice President Mike Pence would be in charge of managing the country's response to the virus.

Austria has quarantined 12 people who were in close contact with a couple who were the country's first coronavirus cases.

A second person suffering from the coronavirus died in France after he was admitted to hospital in Paris late on Tuesday.

Italians or people who recently visited Italy have tested positive in Algeria, Croatia, Spain and Switzerland.

Brazil confirmed Latin America's first infection and the new disease was also detected for the first time in Pakistan, Sweden, Norway, Greece, Romania and Algeria.

South Korea reported 334 additional cases of the new coronavirus on Thursday, the largest daily increase yet, as the US issued a new travel warning for South Korea and a joint military drill was postponed.

Two Germans tested positive for coronavirus, taking the total to 18.

Kuwait's coronavirus cases rose to 25 after 13 more were confirmed and Bahrain's number of infections rose to 26 on Wednesday. The United Arab Emirates has 13 reported cases.

Thailand reported three new cases on Wednesday, taking its total tally to 40.

China has quarantined 257 passengers from two flights from South Korea, Chinese state media reported on Wednesday.

Oil and Asian share markets extended losses on Thursday investors were on edge and sought safety in gold and bonds.

Global stocks have further to run this year, but the likelihood of a correction of 10 percent or more is high, according to Reuters polls of market strategists, with the severity of the economic hit from coronavirus being the biggest risk.

- Reuters