Scientists from Oxford Brookes University, England, looked at hundreds of Instagram posts from people visiting the animals in East Africa and found most tourists were close enough to gorillas to spread viruses and diseases, according to a press release from the university on Tuesday.
"The risk of disease transmission between visitors and gorillas is very concerning," said study lead author Gaspard Van Hamme, an Oxford Brookes University alumnus who started work on the study during his masters program.
"It is vital that we strengthen and enforce tour regulations to ensure gorilla trekking practices do not further threaten these already imperiled great apes."
Mountain gorillas are listed as endangered, with an estimated 1,063 of them left in the wild, according to the release.
They live in the Democratic Republic of Congo (Virunga National Park), Uganda (Bwindi Impenetrable National Park and Mgahinga Gorilla National Park), and Rwanda (Volcanoes National Park).
Researchers looked at 858 photos posted on Instagram from 2013-2019 under two hashtags -- #gorillatrekking and #gorillatracking, said the study. Of that number, 86% showed people within four meters (13.1 feet) of gorillas, and 25 of those photos showed tourists touching gorillas.
Researchers found tourists were close enough to the East African primates to make transmission possible.
"We found that face masks were rarely worn by tourists visiting gorillas and that brings potential for disease transmission between people and the gorillas they visit," said Magdalena Svensson, lecturer in biological anthropology at Oxford Brookes University, in a statement.
Those visiting gorillas in the wild were asked to wear face masks even before the pandemic, Svensson told CNN, as part of "Best Practice Guidelines for Great Ape Tourism" developed by the International Union for Conservation of Nature.
"They're so genetically close to us they can get most of the things we can get" -- such as influenza, Ebola and the common cold, she said.
Now that we know gorillas can catch Covid-19, it is even more important that visitors wear a mask, added Svensson.
Svensson told CNN that visitors are also asked to stay a minimum of seven meters (23 feet) away from the animals, but image analysis shows the average distance has been falling over time.
"It's a huge health risk for them," she said, explaining that even at four meters (13.1 feet) illnesses can be transmitted.
Social media 'expectations'
Social media and the desire to get a good photo to post online could be one explanation, said Svensson. "We know how effective social media is at changing people's attitudes and behaviors," she said.
Gladys Kalema-Zikusoka, from Conservation Through Public Health, a non-profit that works to protect gorillas in Uganda, said: "This research provides a valuable perspective on how much tourists are willing to share their too-close encounters with mountain gorillas through Instagram, which creates expectations for future tourists."
"It highlights a great need for responsible tourism to provide adequate protection while minimizing disease transmission, especially now during the Covid-19 pandemic," Kalema-Zikusoka said in the press release.
Svensson emphasized that visitors provide valuable financial support for conservation efforts and local communities. The solution is not to stop tourism but to better educate people on the risks, she said.
While there is no evidence that wild gorillas have developed Covid-19 thus far, researchers will keep monitoring visitor behavior, added Svensson.
The research was published in the journal People and Nature.
In January, eight western lowland gorillas living at San Diego Zoo were found to have Covid-19. The zoo said on Tuesday that the gorilla troop was back in public view after making a full recovery.