Just over 1,000 mountain gorillas still live in the wild, spread across national parks in Rwanda, Uganda and the Democratic Republic of Congo. Many gorillas have become habituated to humans intentionally to facilitate both research and ecotourism.
The monkeys face a variety of threats, including poaching and habitat loss, but respiratory disease is also a major problem and a leading cause of death in mountain gorillas.
Outbreaks of respiratory diseases have become common among animals. “They happen on a regular basis,” says Dr. Gilardi, who is also a wildlife veterinarian at the University of California, Davis. “And we don’t always know what causes it.”
Bacteria and viruses naturally circulate among gorillas and other monkeys, some of which can cause respiratory infections. But scientists have also documented numerous cases where human pathogens, including the rhinoviruses and coronaviruses responsible for the common cold, made their way into great apes.
In many cases, respiratory viruses cause relatively mild and familiar symptoms in infected gorillas.
“They cough, they sneeze, they have a runny nose, they may have slimy eyes, they may have no food, they are lethargic and literally don’t want to get out of bed in the morning,” said Dr. Gilardi. (Gorillas make and slumber in night nests.) “They look and behave just like we do when we have an upper respiratory infection.”
But these outbreaks can sometimes cause serious illness, including pneumonia, or even death. In 2009, a human respiratory virus sickened 11 out of 12 gorillas in a single family group in Rwanda. Five of the animals required veterinary care and two others, including a baby, died.