Suspected Exposure to Filoviruses Among People Contacting Wildlife in Southwestern Uganda

A red-tailed guenon monkey

Risk factors for filovirus exposure in southwestern Uganda include contact with nonhuman primates, like this red-tailed guenon, duiker antelope and cane rats. (courtesy/Tierra Smiley Evans)

People in the Bwindi region of southwestern Uganda have suspected exposure to filoviruses, particularly those in contact with wildlife, according to a new study led by researchers at the UC Davis One Health Institute and the Bwindi Community Hospital in Uganda. The study, published June 18 in The Journal of Infectious Diseases, is the first report of human exposure to ebolaviruses in the region.

Suspected exposure, but not active Ebola hemorrhagic fever

The study detected ebolavirus antibodies in blood samples from people, indicating likely previous exposure to several viruses that cause Ebola hemorrhagic fever. The study did not detect active filovirus infections among study participants in Bwindi.

Outbreaks of Ebola and Marburg hemorrhagic fever have occurred in neighboring districts, but cases of active hemorrhagic fever have never been reported in this region in humans or in mountain gorillas. Rather, the findings represent either asymptomatic infections or infection with cross-reactive filoviruses yet to be discovered. The study allowed investigators to fill a knowledge gap of how often humans might be exposed to ebolaviruses.

“Exposure to ebolaviruses is probably more common than previously thought,” says Christine Kreuder Johnson, associate director of the One Health Institute at the University of California, Davis, School of Veterinary Medicine. “More studies like this are needed to identify communities most vulnerable to outbreaks of this deadly disease.”

Humans not the only species impacted

Human livelihoods are connected to wildlife in Bwindi, creating a potential for exposure to filoviruses. But the findings may also have implications for the critically endangered mountain gorilla, a heavily monitored great ape population. Human and mountain gorilla health and survival in this region are intimately linked. They are susceptible to the same pathogens, and gorilla tourism supports the local economy, which in turn preserves the forest.

Further investigation needed

Filoviruses were first discovered more than 50 years ago, but the ecology of how these zoonotic pathogens move from wildlife host to a human is still not fully understood. This study identifies human activities and animal species associated with filovirus exposure, including duiker antelope, primates and cane rats. The findings suggest broader surveillance strategies are necessary to better understand the role of secondary hosts in spillover, and add to investigations of bats as likely reservoir hosts.

“These findings should be used to further guide ongoing surveillance efforts following recent ebolavirus outbreaks in West Africa and the Democratic Republic of Congo,” says lead author Tierra Smiley Evans, a postdoctoral researcher with the One Health Institute.

The study was supported by the William J. Fulbright Foundation, the US Agency for International Development (USAID) Emerging Pandemic Threats PREDICT project (grant GHN-A-009-00010-00), and the Intramural Research Program of the National Institute of Allergy and Infectious Diseases, National Institutes of Health.

Media contact

Tierra Smiley Evans, UC Davis One Health Institute, (916) 952-0275,

Media resources

Read the paper (The Journal of Infectious Diseases)