A new mysterious disease made its first appearance last summer in the Arabian Peninsula and has been baffling health experts since. Until now, there have been 103 confirmed cases, with 49 patients dying from the condition (http://www.cdc.gov/coronavirus/mers/). Most patients were originally from Tunisia, Saudi Arabia, Qatar, Jordan and the United Arab Emirates; but the disease is showing signs of spreading with cases already spotted in Italy, UK and France.
Symptoms vary greatly from person to person. Patients who were previously healthy, "tend to get mild symptoms of fever, body aches and upper respiratory symptoms and some are completely asymptomatic", says Saudi Deputy Minister of Health Dr Ziad Memish. Individuals who have underlying previous conditions, "may get severe chest infections with cough and high fever".
When asked about treatments, Dr Memish explains that there are "no approved drugs available for this virus yet, and attempts to use steroids in some patients did not help". We have used combinations of other drugs in some patients, he adds, and the outcome is being reviewed.
The first reported case was identified in June 2012 in a patient in Saudi Arabia. Puzzled by the patient's quickly deteriorating condition, microbiologist Dr Ali Mohamed Zaki went to the Viroscience Lab in Rotterdam, Holland for help. After examination of the samples received, they identified the virus responsible for the unknown condition as belonging to a group of virus called coronavirus (http://mbio.asm.org/content/3/6/e00473-12.long). After a few months of debate, researchers finally agreed to call it Middle East Respiratory Syndrome Coronavirus or MERS for short (http://jvi.asm.org/content/early/2013/05/08/JVI.01244-13.abstract).
Coronaviruses are not new to the scientific community, and are capable of infecting humans and many different animal species. Most infections are relatively mild, and it wasn't until the 2003-03 outbreak of another recently discovered coronavirus - acute respiratory syndrome virus or SARS - that researchers realised that some coronaviruses could actually cause serious and even fatal diseases in humans.
These pathogens are thought to originate in bats, which prompted numerous studies to examine what virus these animals may harbour. In early August, a collaboration between South African and German research institutes revealed the presence of a virus in bats collected in South Africa that is closely related to human MERS (http://wwwnc.cdc.gov/eid/article/19/10/13-0946_article.htm). Sampling 62 bats from 13 different species, the team found evidence for the virus in five animals, setting off speculations about an African origin for the novel virus.
However, researchers may not have to travel that far to find an explanation for the MERS outbreak. Dr Ian Lipkin and his team from Columbia University found a vital new clue less than 12 kilometres from the house of the first victim, in Saudi Arabia. Examining samples from 96 bats, they found that infections with different types of coronavirus were rife, affecting about 1 in every 3 bats. Crucially, there was one animal - an Egyptian tomb bat (Taphozous perforatus) - infected with the same deadly virus (or a very closely related one) as the local patient that died last year, firmly pointing the finger at bats as the source of the virus. (http://wwwnc.cdc.gov/eid/article/19/11/13-1172_article.htm).
However, direct contact between humans and bats is scarce, and researchers expect other animal species to carry the virus and help spread the disease. In search of this mysterious host species, Dr Marion Koopmans, an infectious diseases specialist from the National Institute for Public Health and the Environment in the Netherlands, examined 50 retired racing camels from two herds in Oman, and all animals had antibodies against MERS (http://www.thelancet.com/journals/laninf/article/PIIS1473-3099(13)70164-6/abstract).
"We still need confirmation that the virus that triggers these antibodies in camels indeed is MERS", explains Dr Koopmans, but most likely this indicates that these animals contracted the infection in the past and may be source of exposure to humans. Nevertheless, scientists must continue to test other animal species, she adds, in particular pets with close contact to humans, such as cats and dogs, which could also be acting as an intermediate host. "The bat-camel transmission certainly is one of the hypotheses, but other animals could be involved as well".
These findings don't really solve the mystery, and in fact only add more questions. Are people inadvertently inhaling virus from infected bat droppings or eating food contaminated by bats? Or are sick camels infecting those that work with them? Scientists seem to agree that it all started with bats, but we still don't know how this pathogen is transmitted between these animals and humans, and what other hosts may also be involved.