Two years on from when it was discovered, and after it has caused more than 300 deaths, the Mers coronavirus is still posing myriad unanswered questions for scientists.
How is the virus most easily transmitted? Why has the number of Mers cases shot up this year? Are young camels more likely to pass the virus to people than older animals are?
There are many other uncertainties surrounding this often deadly disease, but with the number of cases having risen dramatically to more than 800 in recent months, the vast majority in Saudi Arabia, efforts to gain a better understanding of the illness and its spread are being redoubled.
The UAE has had at least 70 cases and nine deaths, making it appropriate that Dubai has moved centre stage as part of these research efforts.
Sheikh Mohammed bin Rashid, the Ruler of Dubai and Vice President of the UAE, has initiated a project to test for the Mers coronavirus in the emirate’s camels, after previous studies showed that camels can transmit the condition to humans.
Dubai’s Central Veterinary Research Laboratory (CVRL) will, over the next several months, test 1,000 camels to see if the virus is present in their nasal discharges – which previous studies have indicated can contain large quantities of the virus – their faeces and, if they are lactating females, their milk. As well as camels, the virus is also found in bats and has been linked to rats as well.
Using a technique called polymerase chain reaction (PCR), which creates multiple copies of genetic material that in the case of Mers coronavirus is ribonucleic acid (RNA) rather than DNA, the scientists will determine both whether the virus is present in the various samples, and if so at what concentration.
Blood samples from the camels, which will mostly be drawn from herds across Dubai, will be tested for antibodies to the virus.
A key focus of the study, said Professor Ulrich Wernery, the CVRL’s scientific director, is how the infectivity of camels may vary with age. With previous findings indicating it may be younger camels that are causing most cases of camel-to-person transmission, the centre is testing baby camels, camels aged one to two years old, and fully adult camels, and comparing the results.
“We want to know which group excretes the virus and from where,” he said. “[And] from which age group and then, which is important, [what] is the danger to humans.
“When we find out [camel] adults do not have the virus, we don’t worry about adults and so concentrate on other [age] groups.”
The issue of which age group of camels is most likely to transmit the virus could be linked to the way in which Mers outbreaks tend to be seasonal: upsurges have tended to occur in spring.
That camels tend to give birth in spring has been touted as one possible reason why Mers has tended to become more common in that season.
“It’s a theory that the young camels grow out of it. If the baby camels grow out of it in September, then … the disease is gone [for the year] but we don’t know that. We’re doing this research to find out,” said Prof Wernery.
There have been other possible explanations for the spring upsurge, such as the weather, and some have suggested that this year’s huge increase was due to rapid spread within hospitals. The number of new infections has fallen away since the peak earlier this spring, possibly because of improved infection-control measures in Saudi Arabia, Prof Wernery suggested.
By testing blood samples for antibodies to the virus, it will be possible to determine what percentage of camels in the UAE have been exposed to Mers, as the presence of antibodies indicates that an infection has happened at some time in the animal’s life.
According to reports, in countries including Egypt, Nigeria and Ethiopia, more than 90 per cent of camels have tested positive for antibodies to Mers or a very similar virus, indicating the animals had been infected at some point in their lives.
In tests from Kuwait and Egypt, fewer than 10 per cent of animals were positive for the virus itself, indicating a current infection.
Samples have already begun arriving at the CVRL and will be tested by a five-strong team at state-of-the-art facilities designed to ensure the laboratory workers themselves are not at risk of becoming infected.
Similarly, veterinarians collecting the samples will wear gloves and mouth protection to ensure they too do not become infected.
It is likely to take two to four months before conclusions can be drawn, after which Prof Wernery plans to publish the results in a scientific journal.
Valuable though the data are likely to be, scientists caution that many unanswered questions linked to the transmission of Mers will remain. This is largely because camel-to-person transmission is not thought to be responsible for the majority of human Mers cases.
“Most people who have caught Mers have not had any contact with a camel, which means that the virus is spreading in some other way, probably from another animal,” said Dr Ben Neuman, a virologist at the University of Reading in the United Kingdom who has published extensively on coronaviruses.
“There is still an important missing link in the chain of transmission, and finding that link may be the key to stopping new outbreaks of Mers.”
Ian Jones, a professor of virology at Reading University, said he was “quite optimistic” Mers would eventually be brought under control, although he too said finding what is causing new outbreaks is vital.
“The source of infection is key – once it is discovered then guidelines to avoid contact can be put in place,” he said.
Until that advance is made, Dr Neuman believes Mers is likely to remain a threat and echoing official guidelines, he said people should avoid contact with camels if possible.
“While Mers looks like it will be controlled this year, if we have not found the main source of infection, I would expect the virus to reappear next spring,” Dr Neuman said.
Updated: June 21, 2014 04:00 AM