Epidemiologists investigating a new respiratory virus that has killed 38, say it spreads easily between people and is more deadly than SARS.
More than 60 cases of Middle East Respiratory Syndrome have been reported so far, mostly in Saudi Arabia.
The new coronavirus is related to SARS, which claimed 800 lives following the 2003 pandemic .
Researchers probing MERS say it can spread quickly, particularly in hospitals and one sufferer can infect many.
The fatality rate of the MERS in Saudi Arabia stands at 68 percent, 60 percent higher than SARS.
Symptoms usually involve an initial fever and cough before pneumonia develops.
The origin of the virus is unknown, but it is thought that animals are involved, either bats, camels or goats.
One hypothesis is that infected bats may be contaminating foods like dates.
Medics admit a reliable method of treatment is yet to be found.
What is the new virus?
The Novel Coronavirus (NCoV) that has been identified by the World Health Organisation (WHO) is a strain of coronavirus that has so far infected 34 people, 18 of whom have died since September 2012. Symptoms include fever, coughing, breathing difficulties, pneumonia and, in severe cases, kidney failure. NCoV has been detected in Saudi Arabia, Jordan, Germany, the United Kingdom and France.
What is a coronavirus?
Coronaviruses are a family of viruses that cause respiratory infections in humans and animals. They range from the common cold to SARS (Severe Acute Respiratory Syndrome). The new virus, NCoV, is not SARS.
What is SARS?
An outbreak of Severe Acute Respiratory Syndrome (SARS) was detected in 2003, having begun in China and other parts of south-east Asia before spreading to Europe and the Americas. Of around 8,000 known infections, 774 people died worldwide according to the WHO. There have been no known cases since 2004.
What are the risks of NCoV?
Much remains to be learnt about NCoV, including how it spreads and how to treat it. It is not thought to be very contagious but the WHO believes it may be passed from human to human via droplets in the air when an infected person coughs or sneezes. Although the virus, at this stage, seems unlikely to become a pandemic, health officials are concerned about its potential to evolve and spread. There is no known vaccine; people are advised to avoid close contact with others who show signs of common cold symptoms such as coughing and sneezing, and to maintain good hand hygiene with regular hand-washing.