Despite its high current death rate, the Middle East Respiratory Syndrome (MERS) that emerged in Saudi Arabia last year is unlikely to cause a SARS-like epidemic because it is not spreading as easily, scientists said today.
In the fullest clinical analysis yet of the new virus, British and Saudi researchers said that while there are many similarities between MERS and severe acute respiratory syndrome (SARS), which emerged in China in 2002 and killed around 800 people worldwide, there are also important differences.
The new respiratory virus appears to make people sicker faster than SARS, but doesn't seem to spread as easily, according to the latest detailed look at about four dozen cases in Saudi Arabia.
Since last September, the World Health Organization has confirmed 90 cases of MERS, the Middle East respiratory syndrome, including 45 deaths. Most cases have been in Saudi Arabia, but the mysterious virus has also been identified in countries including Jordan, Qatar, Britain, France, Germany, Italy and Tunisia. MERS is related to SARS and the two diseases have similar symptoms including a fever, cough and muscle pain.
The WHO issued its travel guidance on Thursday for pilgrims going to the annual haj in Saudi Arabia and said the health risk posed by the MERS virus was "very low".
Ali Zumla, a professor of infectious diseases and international health at University College London, said the evidence from his study suggested a large MERS epidemic with many hundreds of deaths was unlikely.
He noted that MERS was first identified 15 months ago and there have been 90 cases reported so far. SARS, spread far more rapidly, infecting more than 8,000 people between November 2002 and July 2003.
An earlier study of how the MERS virus infects people found that the receptors it binds to are common in the lungs and lower respiratory tract and but not in the nose, throat and upper respiratory tract. Some experts think this is why MERS is not currently spreading easily from one person to another.
The study found that MERS killed around 60 per cent of the patients it infected who also had other underlying illness such as diabetes or heart disease. But Ziad Memish, Saudi Arabia's deputy public health minister, who led the research, said this high death rate "is probably spurious due to the fact that we are only picking up severe cases and missing a significant number of milder or asymptomatic cases".
"So far there is little to indicate that MERS will follow a similar path to SARS," he said. The vast majority of MERS cases have been in Saudi Arabia or linked to people who contracted the virus there.
As with SARS, MERS patients had a wide spectrum of symptoms. Most of those admitted to hospital had fever, chills, cough, shortness of breath and muscle pain. A quarter also had gastrointestinal symptoms, including diarrhoea and vomiting.
But unlike with SARS, most MERS cases were in people with underlying chronic medical conditions including diabetes, high blood pressure, heart disease and chronic renal disease. A study by French researchers last month said MERS had not reached pandemic potential and may just die out.