It just takes one, and so far that’s what scientists investigating the Middle East respiratory syndrome outbreak have found — a bat infected with the identical virus that was isolated from human patients.
The bat, known as an Egyptian tomb bat, ends a year-long mystery to find the source of the Middle East respiratory syndrome coronavirus (MERS-CoV) after the first case emerged last summer from Saudia Arabia, not far from where the bat was found.
While other animals, including the camel, have been fingered as possible carriers, none of the viruses isolated from these animals were a complete match with those extracted from infected people. But the MERS harbored by the Egyptian tomb bat proved to be a 100% match, say researchers from Columbia University’s Mailman School of Public Health, EcoHealth Alliance and the Ministry of Health of the Kingdom of Saudi Arabia, who announced their findings in the U.S. Centers for Disease Control journal Emerging Infectious Diseases.
As of early August, the World Health Organization (WHO) reported that a total of 94 people have been infected and 46 have died from the infection. The virus, which is related to the virus that caused a worldwide outbreak of severe acute respiratory syndrome in 2003, leads to severe respiratory distress, pneumonia, fever and coughing. MERS has appeared in nine countries, but all of the patients have been in the Middle East, where the infection likely originates. While MERS infections cause illness about five days sooner than SARS, so far the new virus appears to be less adept at spreading from person to person.
In order to confirm their findings, the researchers collected samples from bats in seven different regions of Saudi Arabia for six weeks. Using DNA sequencing techniques, they identified a significant range of coronaviruses in about a third of the samples. However, one fecal mater sample from an Egyptian tomb bat that was found near the home of the first known MERS-CoV case was genetically identical to that isolated from that person.
But Dr. Ziad Memish, the Deputy Minister of Health in the Kingdom of Saudi Arabia, said there is still no evidence of direct exposure of the virus between bats and humans. While it’s possible for people to contract diseases from like rabies from bats, that usually occurs through eating food that was contaminated by the animals since direct contact or biting is unlike because of the bats’ generally nocturnal habits.
That’s why most public health officials believe an intermediary animal is also involved in the latest outbreak; that’s where the camels could come in. Scientists at the National Institute for Public Health and the Environment in Bilthoven, the Netherlands, suggested that, based on their genetic analysis of camels in the Middle East and elsewhere, dromedary camels could be serving as hosts of the disease and passing it on to people. The researchers studied a variety of animals such as cattle, goats and camels for their ability to harbor the virus. All the camels they sampled from Oman, which is near the first reported case, had antibodies to MERS Co-V, which hinted that the animals had been exposed to the virus and were developing immune defenses against it.
And given that regions that have reported cases of the disease — Africa, Saudi Arabia and the United Arab Emirates — are major breeders of camels for racing as well as for their meat and milk, it makes sense that camels may be the bridge between bats and people when it comes to MERS. As TIME reported earlier this month, the close quarters in which breeders keep domesticated camels provide just the right environment for the virus to mutate, become more virulent and more adaptable to a variety of hosts, including humans.
The research team is therefore continuing to investigate the chain of transmission, studying more camels, sheep, goats and cattle to determine how the virus jumped from the bats and into human hosts. But at least they now have a starting point, and that knowledge could also help to control spread of the virus from infected bats.