Recent research carried out in West Africa has shown that humans are fatally infecting chimpanzees with our common cold viruses.
Primatologist Sophie Kondgen, from the Robert Koch Institute in Berlin, examined clinical samples collected during from ill chimpanzees during respiratory disease outbreaks at a research site in the Cote D'Ivoire between 1999 and 2006. During the outbreaks 92% of the animals at the study site developed symptoms and up to 20% of them subsequently died with the majority of fatalities affecting very young animals.
The results of the analysis were surprising because the same two viral offenders were identified in all of the samples collected from the stricken animals. The culprits were two human viral infections called RSV - respiratory syncitial virus, and HMPV - human metapneumovirus, both of which causes coughs and wheezy symptoms in young children and more mild infections in adults. Intriguingly, tests on the viruses showed a series of characteristic genetic changes. The same molecular fingerprint had emerged shortly before in humans in South America, proving that the animals were almost certainly picking up the infections through human contact.
There are several possibilities to account for how the agents are spreading to the chimps including poaching and tourism, but researchers themselves, because they spend long periods of time making observations close to the animals, are also prime suspects.
Kondgen and her colleagues, who are about to publish their findings in Current Biology, think that the viruses themselves are necessarily fatal to the animals but instead make them susceptible to bacterial infections, triggering a fatal pneumonia. But is the solution to ban humans from getting close to the animals?
It's difficult because, as the team point out, human presence on the one hand is good for the chimps' survival because it deters poachers, and the revenue from tourism encourages conservation. Instead, to tackle the problem, the researchers suggest mandatory vaccination programmes for visitors, removal of human waste that could be infectious and the wearing of face masks capable of blocking the spread of viral particles.