A mysterious SARS-like virus has spread around China with more than 200 diagnosed cases in the cities of Wuhan, Beijing and Shenzhen, plus two people infected in Thailand and another case confirmed in Japan. Here are a few key points about coronavirus.
What is coronavirus?
The UN's health agency says that the outbreak of the disease in Wuhan is a never-before-seen strain. It belongs to a broad family of viruses that range from the common cold to more serious illnesses such as SARS.
According to Arnaud Fontanet, head of the department of epidemiology at the Institut Pasteur in Paris, the new strain is the seventh known type of coronavirus that humans can contract.
"We think that the source may have been animals sold at market and from there it passed to the human population," he told AFP.
The World Health Organization (WHO) says an "animal source seems the most likely primary source... with some limited human-to-human transmission occurring between close contacts".
The outbreak has caused alarm because of the link with SARS (Severe Acute Respiratory Syndrome), which killed 349 people in mainland China and another 299 in Hong Kong between 2002 and 2003.
Fontanet said the current virus strain was 80 percent genetically identical to SARS, which also causes severe breathing problems.
A total of 201 people have now been diagnosed with the virus in China, and the outbreak has already claimed three lives.
Time to panic?
Fontanet said that the coronavirus appeared to be "weaker" than SARS in its current form, but cautioned that it could mutate into a more virulent strain.
"We don't have evidence that says this virus is going to mutate, but that's what happened with SARS," he said.
"The virus has only been circulating a short time, so it's too early to say."
There already appear to have been some cases of person-to-person contact however -- a key feature of past pandemics.
The authorities in Wuhan said over the weekend that some of the new cases had no history of contact with the seafood market believed to be the centre of the outbreak.
Jeremy Farrar, head of the health charity Wellcome, said "it's clear that there is some level of person-to-person transmission" of the coronavirus.
Given the levels of air travel in Asia, there was a risk of widespread contamination, said his colleague Mike Turner.
"We are all more concerned than we were three days ago," he added.
"One of the consequences of a more connected world is that outbreaks have the potential to spread internationally much more rapidly than was the case 50 years ago."
Scientists with the MRC Centre for Global Infectious Disease Analysis at Imperial College, London, warned in a paper last week that the number of cases in Wuhan was likely to be close to 1,700 -- much higher than the number officially identified.
They also said that human-to-human transmission could not be ruled out and recommended extended surveillance inside China.
The WHO has advised that individuals should protect themselves against the virus by thoroughly washing their hands, covering their noses when they sneeze, thoroughly cooking meat and eggs, and avoiding close contact with wild or farm animals.
On Friday the US Centers for Disease Control and Prevention said they would be conducting greater screening of passengers arriving on direct or connecting flights from Wuhan.
Lessons learned?
Fontanet said health workers in China had responded admirably by rapidly carrying out testing among patients and tracing the cases to the market in question.
"We've learned some lessons from SARS. We're better armed and more reactive," he said.
Adam Kamradt-Scott, an expert in the spread and control of infectious diseases at the University of Sydney, said China had "has been quick to share the genome sequencing of this novel coronavirus.
"This has enabled the identification of this new case in Japan," he said.
Such transparency was in contrast to the start of the SARS epidemic, said Fontanet, when China "hid the story for two or three months" at the start of the outbreak.
