Two health workers in Saudi Arabia have become infected with a potentially fatal new SARS-like virus after catching it from patients in their care - the first evidence of such transmission within a hospital, the World Health Organization said.
The new virus, known as novel coronavirus, or nCoV, is from the same family of viruses as those that cause common colds and the one that caused the deadly outbreak of Severe Acute Respiratory Syndrome (SARS) that emerged in Asia in 2003.
"This is the first time health care workers have been diagnosed with (novel coronavirus) infection after exposure to patients," the Geneva-based U.N. health agency said in a disease outbreak update late on Wednesday.
The health workers are a 45-year-old man, who became ill on May 2 and is currently in a critical condition, and a 43-year-old woman with a coexisting health condition, who fell ill on May 8 and is in a stable condition, the WHO said.
France has also reported a likely case of transmission within a hospital, but this was from one patient to another patient who shared the same room for two days.
NCoV, like SARS and other similar viruses, can cause coughing, fever and pneumonia.
Scientists are on the alert for any sign that nCoV is mutating to become easily transmissible to multiple recipients, like SARS - a scenario that could trigger a pandemic.
WHO experts visiting Saudi Arabia to consult with the authorities on the outbreak said on Sunday it seemed likely the new virus could be passed between humans, but only after prolonged, close contact.
Initial analysis by scientists at Britain's Health Protection Agency last year found that nCoV's closest relatives were most probably bat viruses. Yet further work by a research team in Germany suggests nCoV may have come through an intermediary - possibly goats.
The WHO's Wednesday update said that, while some health care workers in Jordan had previously contracted nCoV, these Saudi cases were the first clear evidence of the virus passing from infected patients.
"Health care facilities that provide care for patients with suspected nCoV infection should take appropriate measures to decrease the risk of transmission of the virus to other patients and health care workers," it said.
It also advised health care providers to be "vigilant among recent travelers returning from areas affected by the virus" who develop severe acute respiratory infections.
Since nCoV first emerged and was identified in September 2012, the WHO says it has been informed of a total of 40 laboratory-confirmed cases worldwide, including 20 deaths.
Saudi Arabia has had most of the cases - with 30 patients infected, 15 of them fatally - but nCoV cases have also been reported in Jordan, Qatar, Britain, Germany and France.