As new cases of the novel coronavirus in China are reported and the death toll mounts, health authorities have warned anyone travelling in the affected area to be extra careful.
So far, there have been more than 100 deaths and thousands of confirmed infections from the coronavirus, which emerged in the city of Wuhan in early December, plus many more suspected infections.
With the virus being easily transmitted from person to person, experts said that China may struggle to contain the outbreak.
It can take up to two weeks for the emergence of symptoms, such as fever, shortness of breath or a cough, and even during this “incubation period” people can be infectious. Each person with the virus is thought to be infecting about two others on average.
Air travel is speeding the virus's spread, with cases confirmed in at least nine countries other than China, among them Australia, Japan, Singapore and the United States.
The key advice from health authorities and governments, including those in the United States and the United Kingdom, is simply not to visit China's Hubei province, of which Wuhan is the capital.
Is it ok to travel to China outside of the infected areas?
Professor John Oxford, emeritus professor of virology at the University of London and co-author of the textbook Human Virology, said that it was "perfectly OK" to go to China outside of the infected areas. However, he said all travellers to the country should exercise caution to ensure that they remain safe.
“Don't go into live animal markets anywhere, keep away from accident and emergency departments and keep your hygiene levels up by sensible precautions,” he said.
Outside the affected area the risk to travellers is not thought to be significant.
Anyone who does visit Hubei province should, according to the US Centre for Disease Control and Prevention, be extra careful.
Key measures include good hand hygiene. The CDC suggests that people wash their hands for at least 20 seconds with soap and water or, if these are unavailable, with an alcohol-based steriliser.
Do face masks help to prevent infection?
Experts say that face masks offer limited protection and that it is generally impractical for people to wear the kind of larger respirator masks that could offer genuine benefits.
Other precautions recommended by the CDC include avoiding contact with sick people and with live or dead animals, animal markets and uncooked meat and other animal products. This is because the new virus is thought to have originated in animals.
“Preliminary information suggests that older adults and people with underlying health conditions may be at increased risk of severe disease from this virus,” the CDC said in a briefing document.
Those already in Hubei province are advised to leave, but Wuhan's international airport is closed, bus and train links are suspended and officials are refusing to allow most people to leave the affected area.
What is a coronavirus?
Coronaviruses derive their name from their appearance under the microscope: they are enveloped by a protein structure said to resemble a crown.
Four coronaviruses commonly infect people and these usually lead to mild respiratory infections, such as the common cold.
Aside from the four common forms, which have technical names, another type was responsible for the Severe Acute Respiratory Syndrome (Sars) outbreak in 2002 and 2003. There were more than 8,000 cases of Sars, which also originated in China, but none for more than 15 years.
Sars was much more virulent than the new coronavirus appears to be, since it killed 774 people or almost 10 per cent of those infected.
Prof Oxford said he thought it was unlikely that the new coronavirus would turn out to be a bigger problem than Sars.
“I think it could reach that [level], but not more,” he said. “With all this attention and quarantine, and we have the experience of Sars so we know the public health measures – quarantine, social distance, handwashing – that should knock it on the head.”
Another coronavirus is responsible for Middle East Respiratory Syndrome (Mers), which emerged in Saudi Arabia eight years ago and has killed about 35 per cent of the nearly 2,500 patients known to have been infected, with the UAE among the affected countries.
Most Mers infections are due to person-to-person spread, especially in hospitals, although camels are thought to harbour the virus.
Despite concern over the new coronavirus, officials have said that the risks should be kept in perspective compared to those from other diseases, particularly influenza.
While the number of deaths that influenza causes can change significantly from year to year, in the winter two years ago a particularly severe outbreak killed an estimated 80,000 people in the United States alone, according to the CDC.
As with the new coronavirus, particular groups are more vulnerable, including the elderly and others with a weakened immune system.