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The virus that can lead to pneumonia is believed to have originated in a market selling wildlife in the central Chinese city of Wuhan late last year. It has infected about 80,000 people and killed more than 2700, the vast majority in China.
While radical quarantining measures have helped slow the rate of transmission in China, it is accelerating elsewhere.
Asia has reported hundreds of new cases. On Wednesaday, Brazil confirmed Latin America's first infection and the new disease - COVID-19 - was also detected for the first time in Pakistan, Sweden, Norway, Greece, Romania and Algeria.
Norway's Public Health Agency said one person had tested positive for coronavirus and was being kept isolated at home. The person had returned from China late last week, but did not appear ill and was unlikely to infect others, it said.
A Greek woman who recently returned home from northern Italy became Greece's first case and is being closely monitored, while authorities have ordered the closing of one school in Thessaloniki, the health ministry said.
Germany, which has about 20 cases, said it was already impossible to trace all chains of infection, and Health Minister Jens Spahn urged regional authorities, hospitals and employers to review their pandemic planning.
The World Health Organisation said China had reported 412 new cases on Tuesday, while there were 459 in 37 other countries.
However, WHO chief Tedros Adhanom Ghebreyesus advised diplomats in Geneva on Wednesday against speaking of a pandemic - which the WHO defines as the worldwide spread of a new disease.
"Using the word pandemic carelessly has no tangible benefit, but it does have significant risk in terms of amplifying unnecessary and unjustified fear and stigma, and paralysing systems. It may also signal that we can no longer contain the virus, which is not true."
The WHO says the outbreak peaked in China around February 2, after measures that included isolating its epicentre Hubei province. It said only 10 new cases were reported in China on Tuesday outside Hubei.
FIRST LATIN AMERICAN CASE
Latin America's first case was in a 61-year-old man in Sao Paulo, Brazil, who had recently visited Italy, a new front line in the global outbreak. The diagnosis coincided with the carnival holiday, a peak time for domestic travel.
In addition to Brazil, Italians or people who recently visited Italy have tested positive in Algeria, Austria, Croatia, Greece, Romania, Spain, Sweden and Switzerland. Italy itself has reported more than 400 cases, centred on the industrial heartlands of Lombardy and Veneto.
A hotel in Tenerife in Spain's Canary Islands was locked down over cases linked to Italy.
"It's very scary because everyone is out, in the pool, spreading the virus," said 45-year-old hotel guest Lara Pennington.
In France, a second person has died - a teacher who had not visited any country with a known outbreak.
In Japan, Prime Minister Shinzo Abe called for sports and cultural events to be scrapped or curtailed for two weeks to stem the virus as concern mounted for the 2020 Tokyo Olympics, scheduled to be held from July 24-August 9.
Japan has nearly 170 cases besides the 691 linked to the Diamond Princess cruise ship that was quarantined off its coast this month.
There have been nearly 50 deaths outside China, including 12 in Italy and 19 in Iran, according to a Reuters tally.
South Korea, which with 1261 cases has the most outside China, reported 284 new ones including a US soldier, as authorities prepared to test more than 200,000 members of a Christian church at the centre of the outbreak.
Iraq on Wednesday banned all public gatherings and barred entry by travellers from Kuwait and Bahrain, the health minister said, preventing travel to or from a total of nine countries as fears grew over the spread of the virus.
Iraqi citizens are now banned from travelling to China, Iran, Japan, South Korea, Thailand, Singapore, Italy, Bahrain, and Kuwait, Health Minister Jaafar Allawi said in a decree.
AMERICANS TOLD TO PREPARE
US health authorities, managing 59 cases so far, have said a global pandemic is likely, but President Donald Trump accused two cable TV channels that frequently criticise him of "doing everything possible to make (the coronavirus) look as bad as possible, including panicking markets".
Stock markets across the world lost $US3.3 trillion ($NZ5.2 trillion) of value in four days of trading, as measured by the MSCI all-country index.
Wall Street reversed earlier gains on Wednesday afternoon on fears that the virus would spread across the United States, and oil prices dropped to their lowest level in over a year.
Health officials said dozens of people who had been in China were being monitored in suburbs of populous New York city.
The US Centers for Disease Control and Prevention had also spoken on Tuesday of a nascent pandemic.
"It's not a question of 'if'. It's a question of 'when' and how many people will be infected," said its principal deputy director, Anne Schuchat.
Trump tweeted that he would attend a briefing on Wednesday. But the White House denied a report by the Politico outlet that it was considering appointing a "coronavirus czar".