Mystery outbreak of human viruses is killing chimpanzees in a Uganda forest
- Comes less than two years after first report of chimps dying of common cold
- New study has identified two other respiratory viruses of human origin
- New outbreaks were simultaneous, with one lethal
Researchers has discovered an outbreak of human viruses killing chimpanzees in Uganda.
Less than two years after the first report of wild chimpanzees in Uganda dying as a result of a human ‘common cold’ virus, a new study has identified two other respiratory viruses of human origin in chimpanzee groups in the same forest.
Researchers say the new outbreaks were simultaneous, with one lethal.
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This 2-year-old chimp named Betty succumbed to a human common cold virus in Uganda. The opportunity to retrieve Betty’s body before it decomposed or scavengers set in was critical to making the discovery.
WHAT KILLED THE CHIMPS?
Viral genetic material from the Ngogo chimps revealed infection by metapneumovirus, which is known to cause deadly disease in chimps across Africa.
Surprisingly, the Kanyawara chimps contained the genetic material of a different virus, parainfluenza virus 3.
Parainfluenza virus 3 is a common cause of croup in preschool children.
‘This was really shocking,’ says Goldberg.
‘At the time, we were convinced that the same virus must have been causing both outbreaks, especially considering that the outbreaks were happening at exactly the same time.’
The outbreaks affected different chimp communities in the same forest at the same time, between December 2016 and February 2017.
One group, consisting of 205 chimpanzees known as the Ngogo community in Uganda’s Kibale National Park, was especially hard hit, with almost 44 percent of the animals in the group suffering from respiratory illness.
Twenty-five chimps in the Ngogo group died during the outbreak.
The other group of chimpanzees, knows as the Kanyawara community and consisting of 55 animals, experienced an outbreak where a little more than 69 percent of animals were affected by respiratory illness.
In contrast to the Ngogo group, no animals from the Kanyawara community died of the disease.
‘These are very common human viruses that circulate worldwide and cause ‘the sniffles’ in kids,’ Tony Goldberg, a University of Wisconsin–Madison professor, said.
‘In people, they are no big deal unless the patient has asthma or another underlying condition.’
In chimpanzees, however, the viruses were much more virulent.
‘The chimps cough and sneeze and lie on the forest floor looking miserable. And they lose a lot of weight.’
UW–Madison epidemiologist Tony Goldberg investigating primate disease in Africa. He was dismayed to discover that a human common cold virus was killing healthy chimps
‘It’s heartbreaking to watch these animals suffer, not only from the disease but also from grief over the loss of members of their society.’
One infant chimp at Ngogo cried for hours after her mother died from the illness, Goldberg says.
The baby clung to her mother’s body before finally wandering off to find the rest of the group.
According to Goldberg, a human origin for both viruses can be inferred because the viruses in the chimps were nearly identical genetically to common strains found in people.
Writing in the journal Emerging Microbes and Infections, the team said they believe the viruses must have been introduced by humans in the area.
‘It is remarkable that the majority of the chimp population was affected, suggesting that there was no preexisting immunity and that this virus was newly introduced, perhaps from a human source.’
‘It could happen in any number of ways,’ says Goldberg.
‘Local villagers, researchers, tourists, and many other people visit forests where apes live. All it takes is one person unwittingly carrying a ‘common cold’ virus to spark a deadly outbreak in apes.’