New evidence shows that camels are likely the source of the ongoing outbreak of Middle East Respiratory Syndrome, or MERS, a viral respiratory illness that has led to the deaths of more than 100 people, according to a new study published in the journal mBio and the latest Bloomberg news report.
Researchers at the Center for Infection and Immunity at Columbia University’s Mailman School of Public Health, King Saud University, and EcoHealth Alliance extracted a live, infectious sample of MERS coronavirus (MERS-CoV) from two camels in Saudi Arabia. They found that this sample matched the virus found in humans on a genetic level.
“Here, we report recovery of MERS-CoV from nasal swabs of dromedaries (Arabian camels), demonstrate that MERS-CoV whole-genome consensus sequences from dromedaries and humans are indistinguishable, and show that dromedaries can be simultaneously infected with more than one MERS-CoV,” study authors wrote. “Together with data indicating widespread dromedary infection in the Kingdom of Saudi Arabia, these ﬁndings support the plausibility of a role for dromedaries in human infection.”
The Global Impact of MERS
MERS-CoV can be spread from person to person and is different from other coronaviruses previously found in humans. Symptoms include cough, fever, shortness of breath, and, all too often, death. Currently, there is no vaccine and no cure for the virus, according to the Centers for Disease Control and Prevention (CDC).
At the time of this study, 212 cases of MERS-CoV had been reported in humans since April 2012, and 88 of those patients died, the study authors wrote. That number has now climbed to 339 reported cases of MERS, resulting in the deaths of more than 100 people, according to Bloomberg.
So far there are no reports of anyone in the U.S. being infected with the virus. However, countries with lab-confirmed MERS cases include France, Italy, Jordan, Kuwait, Malaysia, Oman, Qatar, Tunisia, Saudi Arabia, the United Arab Emirates, and the United Kingdom, according to the CDC. The first case of MERS has also recently been reported in Egypt. The infected man had returned from working in Riyadh, the capital city of Saudi Arabia, according to a Reuters news report.
The Search for the Source
Previous research led scientists to believe that MERS had likely come from an animal source. A 100 percent genetic match of the virus was discovered in a bat near the location of the first known case of MERS in Saudi Arabia, according to the CDC. However, a lack of evidence of exposure to bats in the majority of human cases led researchers to believe a second animal was also involved, according to researchers involved in the study of MERS and bats.
Previous research by the same team involved in the current study of camels and MERS also found that three quarters of camels in Saudi Arabia carry the MERS virus, co-author Abdulaziz N. Alagaili, Ph.D., said in the study’s press release.
“We know that the virus has infected camels in the Arabian Peninsula since at least the early 1990s,” said senior author Dr. W. Ian Lipkin, in an interview with Healthline. “We don’t know when it first jumped into humans or how it did so. The receptors needed for the virus for infection are present on both camels and humans.”
Camels Are the Culprits
In order to determine whether camels were the missing link in the spread of MERS-CoV in humans, researchers examined nasal samples collected during a countrywide survey of Arabian camels. The scientists had the virus genome sequenced from the two camels with the highest viral load. They also gathered nasal samples from several other camels that carried the virus.
The genetic sequences were identical to human MERS-CoV sequences, the researchers said. Moreover, the analysis revealed that camels can carry more than one strain of MERS in their bodies at one time.
“The finding of infectious virus strengthens the argument that dromedary camels are reservoirs for MERS-CoV," said study author Thomas Briese, Ph.D., in a press release. "The narrow range of MERS viruses in humans and a very broad range in camels may explain in part why the human disease is uncommon: because only a few genotypes are capable of cross-species transmission.”
The Quest for a Treatment
Based on the results of this study, the next step is to “investigate potential routes for human infection through exposure to camel milk or meat products,” Alagaili said in a press release.
Scientists also still need to know “how people become infected, why some develop severe disease and others seem to have no or only mild symptoms,” Lipkin told Healthline.
As for future methods of prevention, Lipkin said, "Vaccines may be useful for camels; however, given that human infection is rare, it is unlikely that a human vaccine will be developed.” He added, “There are efforts to develop antiviral drugs for people who become infected.”
And while “the recent increase in reported cases is a cause for concern,” Lipkin said in a press release, there is “no evidence that MERS-Cov is becoming more transmissible.”
“The risk at present is limited to the Middle East, with the highest risk in Saudi Arabia,” said Lipkin. “Exposure to camels in this geographic region, particularly young camels, should be avoided as should exposure to raw camel meat or camel milk.”
Moving forward, it is “essential that investigators commit to data and sample sharing so that this potential threat to global health is addressed by the entire biomedical research community,” Lipkin said.