A virus causing deadly respiratory diseases in humans can be passed on to mountain gorillas in Central Africa, researchers have found.

Researchers who spent time in Rwanda's Volcanoes National Park said they found traces of human metapneumovirus during post-mortem examinations of two gorillas that died in 2009. The two, a mother and a newborn, were in a group of 12 infected gorillas.

Researchers could not establish the source of the virus that killed the two gorillas. Human metapneumovirus can cause severe colds and pneumonia.

There are only 786 mountain gorillas in the wild that live in Rwanda, Uganda and the Democratic Republic of Congo.

The study published this week in the Emerging Infectious Diseases Journal of the U.S. Centers for Disease Control and Prevention said that while gorilla tourism provides revenue for conservation activities, it poses risks of infection.

Disease concern for gorillas

The study says close genetic similarities between the two — gorillas share approximately 98 per cent of their DNA with humans — has led to concerns that the apes may be susceptible to many of the infectious diseases that affect people.

The study says that while mountain gorillas are "immunologically naive and susceptible to infection with human pathogens," most of the focus has been on how diseases affecting apes can be transmitted to humans.

The report says gorillas' existence is threatened by encroachment on their habitat, poaching and infectious diseases. Diseases account for 20 per cent of all sudden deaths of the apes.

"The potential for disease transmission between humans and mountain gorillas is of particular concern because over the past 100 years, mountain gorillas have come into increasing contact with humans," researchers said in a statement. "In fact, the national parks where the gorillas are protected in Rwanda, Uganda and the Democratic Republic of Congo are surrounded by the densest human populations in continental Africa."

The researchers added: "Also, gorilla tourism, while helping the gorillas survive by funding the national parks that shelter them, brings thousands of people from local communities and around the world into contact with mountain gorillas annually."

The study was conducted by researchers from the non-profit Mountain Gorilla Veterinary Project, the Wildlife Health Center at the University of California, Davis, the Center for Infection and Immunity at Columbia University and the Rwanda Development Board.