Where do MERS-CoV from?

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Dromedary camels are now the center of study for MERS-CoV (Photo grabbed from WIKIPEDIA)
Dromedary camels are now the center of study for MERS-CoV (Photo grabbed from WIKIPEDIA)

Because of the rapid rise in reported infections of Middle East Respiratory Syndrome Corona Virus or MERS-CoV, researchers are struggling to explain where really the virus came from and how it infect human.

After it was first identified in Saudi Arabia in 2012, MERS-CoV infections have been reported throughout the Arabian Peninsula and spread to at least ten other countries. Most confirmed cases have developed severe acute respiratory illness, but the virus also often causes kidney and other organ failure.

Initially, MERS corona virus is suspected to originate from sheep, cattle, goats, and poultry. But according to the report of David Holmes published at The Lancet, studies have ruled out that MERS-CoV were not from sheep, cattle, goats, and poultry.

According to the report, researchers are now turning their focus to dromedary camels. MERS-CoV virus was found in almost all blood samples taken from 358 dromedary camels in Nigeria and 188 camels in Ethiopia, according to a study published online by the Emerging Infectious Diseases journal. In Tunisia, MERS-CoV was found in 54 percent of adult camels, and in all of the animals from southern province.

The findings add to previous studies that have found the virus in camels in Spain’s Canary Islands and Egypt, as well as in several nations on the Arabian peninsula, and suggest that there may be undiagnosed human cases in Africa, researchers from the Netherlands wrote in the study.

Although it’s too early to declare that camels are the primary source of infections in humans, Marion Koopmans, of the Netherlands National Institute of Public Health who is studying the virus said that although we don’t know how the virus transfer to human, she‘s convinced that people and dromedary camels share the same viruses. “Camels shed virus from their nose, and sometimes in stool, which is dropped and may cause environmental contamination. Younger animals seem to be virus-positive more often than adult animals, so the challenge is to look for exposures (direct or indirect) to young camels as the highest risk factor.”

However, a seasonal increase in exposure to young camels alone doesn’t seem a sufficient explanation, according to Ziad Memish, Saudia Arabia’s Deputy Minister for Public Health and professor in the College of Medicine at Alfaisal University in the capital Riyadh. “More than two-thirds of the primary human cases have no links to camels.” One possibility is that another species is acting as an intermediary. Bats have been touted as a possible source after a bat of the Taphozous genus was found to harbour a fragment of the MERS sequence, but contacts between bats and people are so rare that it would seem an unlikely explanation.

Christian Dorsten, a virologist at the University of Bonn, Germany, who is working with local researchers in Saudi Arabia, says similar link between bats and MERS is far-fetched. “There are several aspects in recent hypotheses around MERS and bats that make no biological sense at all. For example, it is not true that Taphozous feeds on dates from which the virus could be acquired. Taphozous is insectivorous.” he explained.

Another possible explanation for the recent surge in cases is that the virus has acquired mutations enabling it to be transmitted more easily between people, but again, Dorsten notes, the facts tell a different story. Many of the recent cases occurred in the port city of Jeddah, and sequences taken of the Jeddah viruses show no hints of any relevant genetic changes says Dorsten. The Jeddah viruses do, however, seem to be a different strain from those causing infections elsewhere in the country, and are probably linked to a hospital-associated outbreak, according to Dorsten. “Without having seen epidemiological data, I predict that most cases detected in Jeddah will be linked quite directly to the outbreak in King Fahd Hospital from where it spread to other hospitals,” Dorsten concluded.

As of today (26 May 2014), there are 664 reported cases and 200 deaths on MERS-CoV and there is still no vaccine or specific treatment available.

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