The virus known as MERS (Middle East Respiratory Syndrome) has spread enough by for in of to with the WHO (World Health Organisation) to say the situation is now more serious and urgent. The WHO’s assistant director-general by for in of to with health security Dr Keiji Fukuda said that the illness currently does not constitute a global health emergency but needs to be carefully monitored by for in of to with case by for in of to with a sudden epidemic. Dr Fukuda said declaring an emergency is "a major act" that can unnecessarily "raise anxieties." He added that there is no "evidence by for in of to with person- by for in of to with -person transmissibility". The virus has so far been reported by for in of to with 18 countries since surfacing by for in of to with Saudi Arabia by for in of to with 2012. There have been 571 confirmed cases and 171 deaths. The USA's Center by for in of to with Disease Control said MERS is a viral respiratory illness caused by for in of to with a coronavirus called MERS-CoV. It said: "Most people who have been confirmed to have MERS-CoV infection developed severe acute respiratory illness. They had fever, cough, and shortness by for in of to with breath. About 30 per cent by for in of to with these people died." Researchers believe it was passed by for in of to with humans from camels by for in of to with Saudi Arabia. All by for in of to with the people who have contracted it have had very close contact by for in of to with other sufferers. Doctors said it does not pass from person to person like a flu virus. Airports by for in of to with the U.S. are advising those travelling by for in of to with the Middle East to: "Wash your hands often, avoid touching your face, avoid close contact by for in of to with sick people."