Long before COVID-19 forced most of the world behind masks and into isolation, viral diseases had been persistently jumping from humans to primate species, with drastic consequences.

The problem became particularly stark on Dec. 31, 2016, when a viral outbreak was detected at a field site for research on chimpanzees, called Ngogo, in Uganda’s Kibale National Park. The outbreak, from a virus that originated in humans, ultimately killed 25 of the nearly 200 Ngogo chimps, which researchers have studied for 30 years.

A new study led by a University of Arizona primatologist, published in the journal Biological Conservation, provides clear evidence that protocols such as quarantining, masking and more—those that became familiar during the pandemic—can help prevent outbreaks like the one at Ngogo.

The research could shape best practices to help keep chimps and other ape species safe—not only at research sites like Ngogo, but also at conservation sites that welcome swaths of tourists, said Jacob Negrey, an assistant professor of anthropology in the College of Social and Behavioral Sciences and the study’s lead author. Healthy chimps that humans can continue to study and appreciate, Negrey said, can ultimately lead to a better understanding of humans.

“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, who is co-director of the Ngogo Chimpanzee Project, the nonprofit organization that runs the research site in western Uganda. “The kind of trends we’re documenting here are really relevant to all of these human-chimpanzee interactions, not just ones related to research.”

Research at Ngogo began in 1994. The area is now a leading site for chimp research thanks to the size of the chimp population and its isolated location deep in the rainforest. The site is frequently featured in the media, notably in Netflix’s 2023 documentary series “Chimp Empire.”

Negrey has done fieldwork at Ngogo for 12 years, studying the factors that affect chimps’ health, especially age-related diseases and viruses. His work typically involves rising before dawn at a campsite in the rainforest before venturing out to find the chimps, observe their behavior and collect samples of their biological waste.

“You can be wandering through the forest and then there’s rustling and you realize you’ve almost walked into a herd of elephants,” Negrey 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.”

The waste researchers collect is analyzed in labs, and the health data born out in the samples is logged for later study.

Long-standing conservation questions

How to keep chimps—and other animals—safe from human disease has been a long-standing question for conservation researchers, Negrey said.

Long before the outbreak on the eve of 2017, researchers at Ngogo adopted protocols from the International Union for Conservation of Nature intended to keep the chimps safe from human disease. They included a requirement for humans to stay at least 15 feet away from the chimps, more strictly discouraging researchers from leaving their own biological waste in the forest—or burying it if they had to leave it behind—and discouraging researchers from working when they showed symptoms of infection.

“But there was never any systematic study showing that they were effective,” Negrey said of the protocols. “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.”

The outbreak was contained by Feb. 8, 2017, and researchers then added a slate of new health protocols: Researchers with any symptoms were prohibited from entering the forest until they were healthy. Those working in the forest were required to stay about 20 feet from the chimps, with a preferred distance of closer to 30 feet. They also had to wear masks and regularly sanitize their hands when in the presence of chimps and wore different sets of clothes in the forest than those they wore at camp.

And at the start of the COVID-19 pandemic in 2020, researchers who traveled to the forest from abroad had to be quarantined for a week before going inside to work.

All the stricter protocols, including the quarantine procedure, remain in place today, Negrey said.

Negrey’s latest study relied on data from nearly 70 samples of chimp waste, collected between 2015 and 2019, to show changes from before, during and after the outbreak, as health protocols became increasingly strict. Lab analysis helped researchers find DNA in the samples from viruses that came from humans.

There was a clear decrease in the amount of viral shedding from the chimps in the data collected after the stricter protocols were implemented in early 2017, Negrey said. Researchers also observed fewer instances of chimps with persistent coughs: Chimps coughed 1.73% of the time before the protocols, but only 0.356% afterward. Following the weeklong quarantine protocol in 2022, the coughing rate dropped 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.

Understanding chimps to understand humans

Negrey, who joined the U of A in 2023, became fascinated with primates as a kid, first obsessing over gorillas at the zoo. After starting his undergraduate studies at Miami University in Ohio as a journalism major, a chance encounter with a primatologist nudged him toward anthropology. He’s since honed his research focus to understanding the factors that impact chimps’ health.

As one of the human species’ closest living relatives, chimps, Negrey said, are important to study to get a better understanding of humans.

“They’re so special, they’re so weird, and they’re really unlike anything else on Earth,” he said. “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.”