FLICKR, NIAIDScientists studying the zoonotic disease caused by the Middle East respiratory syndrome coronavirus (MERS-CoV) have thus far focused largely on camels, one confirmed animal reservoir of the pathogen. Researchers have also found evidence to suggest the virus may have originated in bats. But a recent finding—MERS antibodies in two people who handle non-camel livestock in northeast Africa—reinforces the idea that camels and bats may not be the only animal reservoirs of MERS-CoV, and suggests that the virus may be endemic to another region, beyond its namesake.
Researchers at the Nairobi, Kenya-based International Livestock Research Institute (ILRI) and at the University of Bonn Medical Center in Germany have found evidence of MERS-CoV antibodies in archived blood samples from two of 1,122 Kenyan livestock handlers, collected between 2013 and 2014. Both people whose blood showed signs of past MERS-CoV infection—a 26-year-old woman and 58-year-old man—were asymptomatic and kept livestock other than camels, the researchers report in the May 2016 issue of Emerging Infectious Diseases. Camels do roam the counties in eastern Kenya where both livestock handlers live, and—as in the Middle East—people in the region consume camel products.
While there have been confirmed cases—even an outbreak—of MERS outside the Middle East, all of these to date have been linked to importations by people who had traveled to the affected area. This study is the first to report non-travel-associated cases of MERS-CoV infection in Africa.
“The absence of autochthonous human MERS-CoV infections in Africa has triggered hypotheses regarding differences in disease transmission between Africa and the Arabian Peninsula and has raised doubts regarding the role of camels as a source of infection,” the researchers wrote in their paper. “Our study provides evidence for unrecorded human MERS-CoV infections in Kenya and the proportion of seropositive specimens that we found is comparable to previously reported proportions of unrecorded infections in the general population in Saudi Arabia.”
MERS is likely underdiagnosed in Africa, the researchers reported. Viral diversity may be in part to blame, according to ILRI’s Joerg Jores. “We need to collect more data to understand any diversity in the MERS virus found, for example, in Kenya and Saudi Arabia, and how the virus spreads,” Jores, a coauthor on the study, wrote in an email.
Beyond underdiagnosis, the finding provides additional clues for epidemiologists studying the origins and spread of MERS. “The presence of antibodies [in two people in Kenya] suggests that the disease may have been endemic in the area since time immemorial,” said Kenneth Mbai, a lecturer in veterinary medicine at University of Nairobi, who was not involved in the research.
Thomas Manga, an assistant director of veterinary services in Kenya’s livestock development ministry, said additional evidence for this immunity hypothesis is needed. “The presence of antibodies to the virus indicates that the people were infected with the virus sometime in the past and . . . is not necessarily associated with clinical disease,” said Manga, who was not involved in the research.
For now, said Jores, figuring out how people are infected with MERS-CoV is key. “We need to know more about the epidemiology of the pathogen, especially in Africa,” he wrote in an email.
A. Liljander et al., “MERS-CoV antibodies in humans, Africa, 2013–2014,” Emerging Infectious Diseases, doi: 10.3201/eid2206.160064, 2016.