It is a year since the World Health Organisation officially named a new virus that had never before been seen in humans and was killing almost half the people it infected.
The Middle East Respiratory Syndrome Coronavirus was billed as the new Sars, the viral respiratory disease that killed hundreds in 2003. Many thought it was only a matter of time before airport screening and travel restrictions were introduced.
As its first anniversary approaches, Mers is still with us but the official response is unchanged, and the number of cases is still increasing slowly. As of yesterday the number of laboratory confirmed cases was 254 including 93 deaths, the first being identified in September 2012.
Professor Andrew Rambaut, of the School of Biological Sciences at the University of Edinburgh, says while much has been learnt about the virus there are still big knowledge gaps to be filled if the transmission of Mers-Coronavirus (Mers CoV) is to be stopped.
"I think the fact that it's not spread outside the Middle East in the last two years suggests it's still tied to the camel population," said Prof Rambaut, who has collaborated on Mers-CoV research projects. "Clearly we are getting onward transmission from human to human, but there are many cases for which this seems to have a direct link to camels. Most of the onward transmission has occurred in hospital or health care environments.
“That suggests to me that the virus isn’t taking hold in the human population. It is being helped along in the health care situations because there are people who are sick and shedding the virus.”
Up to now most of the human-to-human cases have been in health care settings.
“There does seem to be a very high level of hospital transmission or health care based transmission that seems to me could be addressed,” said Prof Rambaut, “and there are lots of protocols since Sars on how to deal with that.”
WHO is clear about what Mers affected countries need to be doing, regularly releasing material highlighting infection prevention and control measures..
These hospital transmissions do not necessarily mean that the virus is getting stronger. Health care facilities often see transmission of viruses and bacteria that are not able to survive as well in the outside world, like Methicillin-resistant Staphylococcus aureus (MRSA).
Fears have been raised recently about a “spike” in cases, suggesting the virus is getting stronger and deadlier. Experts, however, urge caution about spreading such messages.
Dr Mansour Al Zarouni, a medical and molecular microbiologist and executive director of SRL Diagnostics in Dubai, says the outbreak is spreading “slowly but surely”.
“The threat is there, precautions need to be in place both for public as well as health care workers,” he says. “And this opportunity could be used to strengthen the processes for infection prevention, especially the transmission of infections in health care settings.”
Dr Al Zarouni, who spent 20 years as director of Pathology and Laboratory Medicine at the Ministry of Health, says countries where Mers is prevalent are conscious of damaging their reputations or economies.
Prof Rambaut suggests the recent increase in reported cases in the UAE is more likely linked to tracing contacts, rather than an increase in incidence.
“I don’t think this is necessarily indicative of a spike in incidence, it’s a more aggressive forms of screening as a result of a parent case.
“It’s not the same pattern that we have seen in Saudi Arabia. Most detected cases have been severe cases and detected because they are severe. They arrive in the hospital and have particular morbidities that are indicative of Mers.
“It’s very difficult to sit here and look at press reports and patch the story together. It’s still a big unknown about how many missed diagnoses there are, particularly of milder cases.
On Wednesday the regional WHO office offered to send “international expertise” to Saudi Arabia and the UAE in light of the current outbreaks to help determine the transmission chain.
Referring to several people who had contracted the disease in a health care setting, WHO said: “Although the majority of the cases had either no or only minor symptoms, and most do not continue to spread the virus, WHO acknowledges that some critical information gaps remain to better understand the transmission of the virus as well as the route of infection.”
The advice to the public is limited but clear. Anyone whose live is likely to be threatened by contracting Mer — the elderly and those with an existing medical condition should avoid close contact with animals when visiting farms or barn areas where the virus could potentially be circulating. People should also adopt good hygiene measures such as regular hand washing when visiting a farm or barn and avoid contact with sick animals.
Because the risk of human-to-human transmission remains low, travel restrictions and border screen remains unlikely. Restrictions are only enforced during a “public health emergency of international concern.” While there have been a limited number of cases diagnosed abroad, the disease has failed to spread.
At the moment, Prof Rambaut says, efforts should be focused on learning more about the virus itself at the source.
“We need to really nail down the connection with camels. Do widespread surveillance in camels and look at the genetics of the viruses we find, and see how widespread and diverse they are, and how much mixing is going on, and ask how we could possibly try to prevent exposure.”
It is important, he says, to look at those cases that have appeared in people who have not had any contact with camels and are not in a health care setting.
“When we are seeing a health care worker who has been caring for a human Mers case, that’s a known problem and it’s known how to address it. If you don’t know where the source is, it will continue to linger on. That’s why it has been lingering on for the best part of two years.”
WHO confirmed in March that while the virus might have originated in bats, it was much more likely that camels are the source of infection for humans.
“As such, discovery of the route of transmission between camels and humans remains critical to stopping the initial introduction into human populations,” it said.
A report released by the Centers for Disease Control and Prevention last week evaluated the prevalence of Mers-CoV in a dromedary adult and calf camel herd in Al Hasa, Saudi Arabia.
A study team from King Faisal University and the University of Hong Kong concluded, after testing adult and calves, that dromedaries might be the natural host for the virus and that nasal aspirates and faecal matter could both be the possible source of transmission to humans.
In November, a WHO report on Mers in humans identified some common characteristics of the laboratory confirmed cases up until that point. The median age was 50 years, and almost two thirds were male. Eight out of 10 people had at least one underlying medical condition, the most common being chronic renal failure, diabetes and heart disease.
The research team classified 51 patients as “sporadic” or index cases, meaning they had no exposure to other known cases, occurred in an area with no recent previous cases or were the first to report symptoms in a cluster of cases. Ninety five had epidemiological links to other diagnosed cases, and there was 17 whose “epidemiological classifications remain unclear as no information about contact with other cases is available.”
Five months on and little has changed in terms of the demographics. The median age of all cases (primary and secondary) remains at 52 years, and 67 per cent are male.
There are two clear messages to be taken from the existing body of the research. The first is scientists must find the exact route of transmission between camels and humans and understand all they can about the virus itself. Second, infection control measures and surveillance in hospitals much be boosted to limit preventible human-to-human transmissions.
“The continued occurrence of transmission between humans in health care settings and in households is an ongoing concern,” says Prof Rambaut.
The likelihood of Mers turning into a pandemic such as Sars, which killed 770 people over two years, is slim. In most cases, Prof Rambaut says, the “big pandemics have become pandemics” before scientists are aware of the virus.
It will be time to worry ifthe virus starts to mutates and becomes stronger. A genetic mutation that allows it to to bind to particular cells, for example, would be a concern.
“The best way of detecting it would be to do very good surveillance and observe if the virus starts to change its epidemiology,” says Prof Rambaut.
Another key factor for epidemiologists when evaluating the threat of a particular virus is the susceptibility of the population.
"It might be that there are many cases in North Africa that have far more camels than Saudi Arabia. It may be that this disease has been happening for years undetected, which again suggests it's not something that's going to take off in a human population.
“The only caveat is if the virus got into some population in which it was able to spread more freely; somewhere where the conditions were such that however it is transmitted is given a high opportunity. Where there’s more transmission of diseases through fecal or oral contact, for example. It’s possible that that would be the kind of environment in which it would do well.
“That would be a concern but there’s no particular evidence [of that].”
For now though, the virus seems to be limited to the Middle East and relatively difficult to catch but until the source has been eliminated, or at least better understood, the threat of spread among the human population remains.
munderwood@thenational.ae