Saudi Arabia’s health minister today warned Saudis on national television to avoid close contact with camels, and not to consume raw camel meat or camel milk, after a report that dromedaries are the “plausible” source of the Middle East respiratory syndrome (MERS) virus. The warning came as a team from the World Health Organization (WHO) arrived in the kingdom to investigate an accelerating outbreak.

Saudi authorities announced 32 new cases of the virus between 26 and 28 April. That makes a total of 345 cases in the country, more than double the 163 reported there between when the virus emerged in Saudi in 2012 and 1 April this year. So far 105 people have died.

Almost all of the worldwide cases have been in the Arabian peninsula, or in people who had just returned from visiting it. Three cases were detected in Malaysia, Philippines and Greece last week, and now Egypt has announced its first two suspected cases, both in people recently back from visiting Saudi.

Where’s the host?

Scattered cases that could not be traced to infection by other people have suggested that the virus is jumping sporadically from an animal host. Some infected people had had contact with camels before falling ill, but virologists had been unable to isolate a whole MERS virus from the few camel samples analysed until now.

Ian Lipkin at Columbia University in New York, Saudi scientists and wildlife disease experts at the EcoHealth Alliance also in New York, have now reported MERS viruses in nasal swabs from Saudi camels, whose complete genetic sequence they describe as identical to viruses from human cases.

“Together with data indicating widespread dromedary infection in the Kingdom of Saudi Arabia, these findings support the plausibility of a role for dromedaries in human infection,” they conclude. As well as solving a puzzle, the work suggests a way to stop MERS in its tracks: a good MERS vaccine for the many domesticated camels in the region.

The team found several varieties of the virus in camels, and only one in humans. This may be good news. If only one of the camel viruses can jump into humans, the team says, it may not have the genetic diversity it needs to evolve into a more threatening human epidemic.

Human to human

As with many viruses that jump to people from animals, MERS seems to spread from human to human with difficulty. The real fear is that it will evolve that ability.

According to the WHO, 75 per cent of recent cases have been caught from another human, many in healthcare facilities. Some 29 per cent of all cases have been in healthcare workers.

The upsurge does not seem to be due to mutations that have made MERS more transmissible, however. Christian Drosten of the University of Bonn, Germany, reported this week that the full sequences of MERS viruses from early April in Jeddah – the epicentre of the upsurge – had no obvious differences from other MERS samples. The sequences do not suggest that “viruses from Jeddah have acquired changes increasing their pandemic potential”, he concludes.

The real reason for the upsurge may be poor infection control in hospitals. In an outburst rare among Saudi commentators, Khaled Almaeena of the Saudi Gazette, a leading English-language daily, wrote on Sunday that “the outbreak of this virus, the rising number of infected people, the increasing death toll and above all the mishandling in communicating what has been happening have caused a panic”. He blames poor conditions in hospitals, especially in Jeddah, for the ongoing epidemic.