A new European study published this week gives the first hint that camels could be a reservoir for the mysterious MERS virus.

Writing in Lancet Infectious Diseases, senior author Dr Marion Koopmans of the Dutch National Institute of Public Health and colleagues, describe finding evidence that the Middle East respiratory syndrome coronavirus (MERS- CoV), or a related virus, has infected camel populations.

They found traces of antibodies to the virus in blood taken from dromedary camels in the Middle East in Oman and on Spain's Canary Islands.

The discovery may help establish how the virus is passing to humans. According to the World Health Organization, since September 2012 the virus has infected at least 94 people and killed 46.

  • MERS is a member of a the coronavirus family which in humans causes illnesses ranging from the common cold to Severe Acute Respiratory Syndrome (SARS).
  • The infection had not been seen in humans before April 2012. In most cases it has caused severe illness, with death occurring in about half of them.
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Although recent studies have found MERS-CoV can reproduce in cell lines taken from bats, which were proposed as a reservoir for the outbreak of the SARS coronavirus that killed 800 people globally about ten years ago, it is thought unlikely that the virus is passing from bats to humans, given that contact with humans is relatively rare.

In their background information, Koopmans and colleagues write:

"Anecdotal exposure histories suggest that patients had been in contact with dromedary camels or goats."

Cows, sheep, goats, camels

For their study, they tested blood samples from cows, sheep, goats, dromedary camels and other camelid species in Oman and other places around the world, including Spain, the Netherlands, and Chile.

They looked for antibodies to MERS, and also antibodies to SARS and another strain of coronavirus called HCoV-OC43, that can also infect humans.

The results showed that 50 of 50 camels from various locations in Oman and 15 of the 105 camels from Spain had protein-specific antibodies against MERS-CoV.

The blood samples from the sheep, goats, cattle and other camelids showed no such signs.

Although the researchers found antibodies to MERS in the camels, it does not necessarily mean the animals are passing the virus to humans. This has yet to be proven.

However, the researchers conclude that their findings show there is widespread infection of MERS-CoV, or a close relative, in the Oman camel population.

There are various ways that dromedary camels can come into contact with humans in the Middle East, where they are a source of meat and milk, and also used for racing.

A group of doctors also warned recently that MERS could spread faster in mass pilgrim gatherings, such as those of Umrah and Hajj that attract millions of people from all over the world to the holy Saudi cities of Mecca and Medina.

Written by Catharine Paddock PhD