MERS Virus In Saudi Arabian Camels Is 'Widespread,' Has Been Present For At Least 20 Years
Scientists announced in December 2013 that Middle East Respiratory Syndrome, or MERS, is found in camels. One month later, a second study found that a number of camels in the United Arab Emirates had the disease as far back as 2003. A study published today in mBio pushes that MERS-camel timeline back even further, all the way back to 1992 or perhaps earlier.
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"Our study shows the MERS coronavirus (MERS-CoV) is widespread," said senior study author W. Ian Lipkin of Columbia University, in New York, N.Y. "Adult camels were more likely to have antibodies to the virus while juveniles were more likely to have active virus. This indicates that infection in camels typically occurs in early life, and that if people get the virus from camels the most likely source is young camels."
The study authors speculate that humans may have first gotten MERS from camels, but the study didn't test whether this was the case. Humans were first infected with MERS in 2012; assuming that camels did infect humans, why would it take so long for us to catch MERS if camels had it back in 1992? The answer may be that the "right" virus hadn't yet developed to make the camel-to-human jump, according to Vincent Racaniello, a professor of microbiology and immunology at Columbia University.
"I would speculate that if camels were infected with a MERS-CoV like virus in 2003, then that virus simply did not have the proper nucleotide sequence to infect humans," Racaniello said last month. (At the time, 2003 was the earliest known instance of MERS in camels.) "It might only take one base change, or a handful, to let the 2003 virus infect humans. Perhaps the 'right' virus had not yet emerged in camels in 2003."
In the mBio study published today, scientists from the United States and Saudi Arabia collected blood samples and rectal and nasal swabs from dromedary camels across Saudi Arabia. The samples, taken in November and December 2013, were analyzed using mobile lab equipment. In addition to the these samples, the scientists analyzed archived blood samples from dromedary camels collected between 1992 and 2010.
Seventy-four percent of the Saudi Arabian camels were found to have MERS-CoV antibodies. More than 80 percent of the adult camels had the antibodies, and in eastern Saudi Arabia, 90 percent of camels aged two years or younger had the antibodies; in the southwest, only five percent did. Camel serum samples from Saudi Arabia dating back to 1992 showed the presence of MERS-CoV antibodies, or to its close relative.
In 35 percent of young camels, nasal swabs showed the virus was active. Taken together, adult and young camels showed an active virus rate of 15 percent. The nasal swabs showed the active virus more frequently than in the rectal swabs, which the scientists said suggested that the virus likely spreads through respiratory secretions.
According to the World Health Organization, there have been 182 human cases of MERS, 79 of which have resulted in death. First reported in humans in Saudi Arabia in 2012, the respiratory illness has been found in a total of ten countries in the Middle East, Africa and Europe. MERS can lead to severe acute respiratory illness, which causes fever, cough and shortness of breath, and can cause death. The coronavirus can be transferred between people in close contact, including from patients to health care providers.
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