Human diseases threaten chimpanzees - but we can protect them

For years before the world knew COVID-19, viruses were already moving from humans to wild animals. Among those affected were chimpanzees, who suffered quietly as diseases crossed species lines.

The issue became urgent on December 31, 2016. At Ngogo, a research site in Uganda’s Kibale National Park, a viral outbreak struck a large chimpanzee community.

The virus, which originated from humans, killed 25 out of nearly 200 chimps. Scientists had been studying these chimps for three decades, making the loss even more devastating.

In a study from the University of Arizona, researchers offer clear evidence that basic safety measures – like masks, distancing, and quarantine – work.

These steps, now familiar because of the pandemic, can protect chimpanzees and other apes not only at research sites like Ngogo but also at tourist destinations where humans and animals interact daily.

Why chimpanzees remain at risk

Jacob Negrey is an assistant professor of anthropology in the College of Social and Behavioral Sciences and the study’s lead author.

“We have really good reasons to think that chimpanzees that are visited regularly by tourists are at even greater risk of this sort of transmission because they’re exposed to a wider range of people on a daily basis,” said Negrey.

“The kind of trends we’re documenting here are really relevant to all of these human-chimpanzee interactions, not just ones related to research.”

Tracking the health of chimpanzees

Ngogo is no ordinary site. Research started there in 1994, and the location’s dense rainforest and large chimpanzee population have made it a top site for primate studies. It’s even featured in Netflix’s documentary series Chimp Empire, released in 2023.

Negrey has spent more than a decade at Ngogo, tracking the health of these chimps. His typical day begins before dawn, setting out from a forest campsite to observe chimp behavior and collect biological samples.

“You can be wandering through the forest and then there’s rustling and you realize you’ve almost walked into a herd of elephants,” he said. “You have to really love the chimps and love the work that you’re doing because there’s a good chance you’re going to be peed on.”

Samples collected in the field are later analyzed in laboratories, providing essential data on the chimps’ health over time.

Human diseases in chimpanzees

The risk of human diseases crossing to chimps has worried researchers for years. Even before the 2016 outbreak, the Ngogo team followed recommendations from the International Union for Conservation of Nature.

The researchers kept a 15-foot distance from chimps, buried any human waste, and stayed away from the forest when sick.

“But there was never any systematic study showing that they were effective,” Negrey explained. “There was just such an urgency to this problem that it was like the solution needed to be put out before we even had evidence of its efficacy.”

After the 2017 outbreak, they toughened the rules. Anyone with symptoms could not enter the forest. Healthy researchers had to keep a distance of about 20 feet – preferably 30. They wore masks, sanitized their hands, and used separate clothing for forest work and camp life.

By 2020, COVID-19 prompted even stricter rules: researchers arriving from abroad quarantined for a week before entering the forest. Today, these safety measures to protect chimpanzees from human diseases remain firmly in place.

Safety protocols are working

The researchers analyzed nearly 70 samples of chimpanzee waste collected between 2015 and 2019. They compared samples from before, during, and after the 2016-2017 outbreak.

The experts found viral DNA from humans in the chimps’ samples – but saw a clear drop in virus presence once strict protocols began.

Coughing patterns of the chimpanzees also changed. Before the new rules, chimps coughed about 1.73% of the time. After the rules, that number dropped to 0.356%. By 2022, after adding the quarantine rule, it fell even further to 0.075%.

“We’re really excited about this study because it actually does show – for the first time, as far as I’m aware – that these protocols work,” Negrey said.

Protecting chimps for future generations

Professor Negrey, who joined the University of Arizona in 2023, found his passion for primates as a child fascinated by gorillas at the zoo. Initially majoring in journalism at Miami University in Ohio, a chance meeting with a primatologist steered him toward anthropology.

Today, Negrey focuses on the health of chimpanzees, especially how they are impacted by diseases and aging. As some of our closest living relatives, chimpanzees offer critical insights into our own species.

“They’re so special, they’re so weird, and they’re really unlike anything else on the planet,” said Negrey. “It’s to our great benefit to protect them for future generations so we can continue to be awed by them and continue to learn from them.”

The full study was published in the journal Biological Conservation.

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