By Matt McGrath
Scientists are soon to test cats, dogs and even rats as they seek to understand the mysterious Mers infection.
Middle East Respiratory Syndrome was first discovered in 2012 and has so far, killed around 200 people globally.
While the virus that causes it has been found widely in camels, researchers say it could be lurking in other species.
One expert told BBC News that the hunt is likely to soon extend to animals that have close contact with people.
Mers was originally found in a patient from Bishah in Saudi Arabia but since then almost 600 cases of the infection have been discovered around the world, with around 30% of those who get sick dying from the illness.
Researchers believe the coronavirus that causes the infection crossed over from animals.
As the numbers of people infected by the virus rose, scientists sought to test common animals in the Middle East for exposure.
Using blood samples from camels in the Canary islands, Dutch researchers found the first antibodies to the disease. They liken these antibodies to footprints, indicating that the virus had once passed through the animal.
A recent study showed conclusively that the version of the virus circulating in humans is indistinguishable from the one that's been found in camels.
However the lead author of that report, Dr Thomas Briese from Columbia University, believes that there are many unanswered questions about the disease.
He points to the fact that if camels were the sole route of infection, then the illness should be more prevalent among those who work with or are in close contact with the animals.
And there have been a small number of cases of people dying from Mers who have no known relationship with camels.
"We do have these sporadic cases where there is no known exposure to known cases and we question where do they catch the virus," he told BBC News.
"In some cases there was animal contact or camel contact but in others not, so there is no clear definitive picture yet."
Dr Briese says that other species, including goats and sheep, have been tested but haven't shown antibodies indicating exposure.
Another report showed that the geographic distributionof the disease in camels is far more widespread than previously thought, with significant reservoirs in Nigeria, Ethiopia and Tunisia.
Adding to the Mers mystery, there have been no reports of people dying from the respiratory infection in these areas.
These unknowns, says Dr Briese, are pushing researchers to extend the search for the Mers coronavirus to domestic animals.
The virus that is circulating in humans is the same as the one found in camels
"The others that we are looking into or are trying to look into are cats, dogs where there is more intimate contact, and any other wild species we can get serum from that we are not currently getting."
The issue of how to tackle Mers will be on the agenda here in Paris, at the congress of the world organisation for animal health (OIE).
Addressing this meeting of veterinarians and ministers, the head of the World Health Organization (WHO), Dr Margaret Chan also struck a note of caution on the role of camels in the spread of the disease.
"Our current concern of course is about the human cases of Mers, I thank OIE for a very balanced scientific assessment on the possible role of camels in the transmission cycle.
"The evidence however is by no means conclusive and we need to know this as we issue advise to the public."
One of their biggest worries about Mers is that the virus will mutate and become more easily spread among humans. So far there is no evidence that has happened.
"It can happen at any time, mutations occur randomly," said Dr Briese.
"The larger the numbers the higher the probability, that's the point of trying to stem these human infections."
Work on the development of a vaccine has shown some progress although it is still highly experimental. Scientists say that if one is developed it will most likely be used on animals like camels and not on humans.
What is Mers?
- It's a type of coronavirus
- These cause respiratory infections in humans and animals
- Symptoms include fever, cough and breathing difficulties
- It can cause pneumonia and sometimes kidney failure
- Experts believe the virus is not very contagious
- They are unclear on the best treatment but advise good hand hygiene to prevent transmission
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