The first human-to-human transmission of the Wuhan coronavirus in Europe has been reported in Germany, where a man was infected by a colleague who had been in China, fuelling anxieties about the potential ease of international spread.

Experts said it was of particular concern that the Chinese woman who originally had the virus apparently had no symptoms when she transmitted it to her colleague. There have been warnings from inside China that people may be infectious before they start to feel ill.

So far there has been very limited spread from China. A handful of countries have reported cases including France, which has three, and the United States, which has five. This is the first reported European case of transmission from one person to another but it has also occurred in Japan, Vietnam and Taiwan.

The World Health Organization said on Tuesday that China had agreed the WHO could send international experts “as soon as possible” after talks in Beijing. It said a better understanding of the virus’s ability to spread from person to person was urgently needed to advise other countries and guide the global response to the outbreak.

Xi Jinping, the Chinese president, said the country was battling a “demon” virus during talks earlier on Tuesday with the UN agency’s head, Tedros Adhanom Ghebreyesus. His comments came after anger simmered on Chinese social media over the handling of the health emergency by local officials.

The vast majority of more than 4,000 cases, however, and all 106 deaths, have been in China and principally in Wuhan, the city where the coronavirus emerged and caused a mass outbreak of viral pneumonia.

Many governments have brought in screening or other controls at airports for arrivals from China. Countries that have said they will repatriate their citizens in Wuhan – including France, Japan and the United States – are making arrangements to isolate them once back on home soil.

On Tuesday evening the UK Foreign Office updated its advice to warn against all but essential travel to mainland China following the coronavirus outbreak.

The travel advice for China on the gov.uk website was updated to say: “The Foreign and Commonwealth Office advise against all travel to Hubei province due to the ongoing novel coronavirus outbreak. If you’re in this area and able to leave, you should do so.

“The Chinese government continue to impose further restrictions on movement within China in response to the coronavirus outbreak. It may become harder over the coming weeks for those who wish to leave China to do so. If you feel that you may want to leave China soon, you should consider making plans to do so before any further restrictions may be imposed.”

Hong Kong has announced major cuts to its transport links with mainland China.

The 33 year-old man who has been infected had not visited China, but a Chinese colleague who visited Germany last week had “started to feel sick on the flight home on January 23”, said Andreas Zapf, head of the Bavarian State Office for Health and Food Safety.

The Chinese colleague, a woman, gave a training session on 21 January at the office of the car parts supplier Webasto in Stockdorf in Bavaria. The man who had attended the session tested positive for the virus on Monday evening. He remains in hospital in an isolation ward, but Zapf said he “was doing well”.

The Chinese woman sought medical attention when she returned from China and was found to have the virus. She is said to have recently visited her parents in Wuhan.

In a statement, the Webasto company said it had halted all business travel to and from China “for at least the next two weeks”.

Health officials are checking 40 people who had been in contact with the two infected workers, recently, including colleagues and family members.

The European Centre for Disease Control said in a statement that the Bavarian case had not changed its assessment of the risk but it expected more similar cases. “At this stage of the ongoing outbreak in the Hubei province in China, it is likely that there will be more imported cases in Europe. As a consequence, it could be expected to see limited local transmission in Europe.

“A single detected case in Europe does not change the overall picture for Europe, nor does it change the assessment that there is currently a moderate likelihood of importation of cases.”

Experts said human-to-human transmission outside China was unsurprising but the German case is concerning largely because the virus appears to have been transmitted by somebody without symptoms, said Paul Hunter, Professor in Medicine at the University of East Anglia.

“The Vietnamese case was reported by WHO and he was in contact with his sick father who had returned from China. The Japanese cases was a tour bus driver who had driven around two groups of Chinese tourists and the German cases had attended a work-based training event also attended by a woman who only became ill two days later during her return to China two days later. The German case is most worrying because if the Chinese woman was indeed asymptomatic at the time of the training session it would confirm reports of spread before symptoms develop making standard control strategies less effective,” he said.

The novel coronavirus is believed to have emerged from wild animals sold for food in the Wuhan seafood market, which has now been closed. It has a fatality rate of about 2%, usually in people who are in poor health with weak immune systems that are unable to fight it off. But experts at Imperial College London who do infectious disease modelling for the World Health Organization believe there are thousands of mild cases that are not being recorded, and that the total may be 100,000 cases already. That would put the death rate far lower.

Symptoms include a sore throat, fever and breathing difficulties. People are warned to protect themselves by hand-washing, because it can be transmitted in skin-to-skin contact, and to cover their nose and mouth if coughing or sneezing. In the UK, the advice is for anyone who thinks they may have been in contact with somebody carrying the virus to stay at home by themselves and call 111 for advice.