Genetic analysis of samples of the deadly Mers virus that has killed 58 people in the Middle East and Europe shows the disease has jumped from animals to humans several times, scientists said yesterday.
At least 132 people have been infected with the Middle East respiratory syndrome (Mers) coronavirus since it emerged about a year ago, and it has killed 58 of them, according to the World Health Organisation.
While cases have been reported in people across the Middle East and in France, Germany, Italy, Tunisia and Britain, the vast majority of infections and deaths are in Saudi Arabia.
After conducting genome sequencing studies of the virus - from the same coronavirus family as the one that caused severe acute respiratory syndrome (Sars) a decade ago - British and Saudi researchers found several infection transmission chains and said they painted a picture of what they called lively "pathogenic chatter" between species.
"Our findings suggest that different lineages of the virus have originated from the virus jumping across to humans from an animal source a number of times," said Paul Kellam, a professor of viral pathogenesis at Britain's Sanger Institute and University College London who led the research.
His team sequenced and analysed the genomes of Mers samples taken from 21 patients from across Saudi Arabia. They then combined the geographic locations of the patients with the time they were infected and the amount of genetic differences seen between the virus genomes.
This led them to what they called a "higher resolution picture of how the virus has spread and how its genome has changed over time".
While the findings, published in the Lancet medical journal, cannot help scientists predict how likely Mers is to become more easily transmissible in people - and how likely to cause a human pandemic - they should help health experts develop more effective infection control measures to limit its spread.
The virus, a cousin of the coronavirus that caused a deadly outbreak of Sars in 2002 and 2003, can cause coughing, fever and pneumonia.
As yet no firm evidence has been found on the so-called "animal reservoir" of Mers, although several recent studies have linked it to bats and camels indigenous to western Asia and North Africa.
Various groups of scientists are conducting studies of other potential reservoir species, including goats, sheep, dogs, cats, rodents and others.
An "intermediary" source may also be possible, as most of the known cases have had no known direct contact with animals, he said. Asked what this source could be, he said this was unclear. Theoretical avenues to explore would include food.
Ziad Memish, Saudi Arabia's deputy minister of health and one of the researchers on this latest study, said pinning down the animal source or sources would be critical in allowing health authorities to get on top of the outbreak.
Researchers and health officials say they take some solace from evidence showing that while the virus can spread from person to person, it does not do so easily and doesn't appear to be gaining a firm foothold as a human disease.
"Two mass gathering events attracting over eight million pilgrims have occurred in Mecca, Saudi Arabia since the discovery of Mers 12 months ago - the annual haj in October 2012 and the July 2013 Ramadan Umrah season - and yet no Mers cases have been reported from these events to date," said Ali Zumla, a professor of infectious diseases at University College London, who also worked on the study.
He added, however, that "despite the current minimal risk of global spread" and in the light of these latest genetic findings, "watchful surveillance and vigilance is required".
Additional reporting by Agence France-Presse