Observations
From the 15th to 18th of October, a new temporary member of staff came to Sonso, R.C., who was sick
for 3 days while at Sonso during which time he went into the forest to observe the chimpanzees with a
field assistant. He had a cough. On the 4th day, he went to hospital for treatment. A field assistant (not
the one he entered the forest with) began coughing 3 days later, and did not go to the forest for one day,
as he was feeling sick.
No changes in weather conditions were noted during the time of the epidemic.
There was no evidence of respiratory disease in any of the other species of primates in the Sonso area:
blue monkey, black and white colobus monkey, red tailed monkey and olive baboon.
An unidentified immigrant female in oestrus came into the group on 10th November and mated with
several males including NK, who was observed to have a cough on 11th November. However this
female did not cough.
Assessment
Based on morbidity data and a lack of serious symptoms, it is likely that the outbreak can be attributed
to one of the following diseases:
Respiratory Syncytial Virus (RSV)—Chimpanzee Coryza Virus
Paramyxovirus 1, 2 or 3.
Influenza A and B
Symptoms were mainly upper respiratory signs, cough and discharge. The disease did not
progress to more serious symptoms. RSV, Paramyxovirus and influenza viruses are often self-limiting
if there is no secondary bacterial infection. Other diseases would have had more serious symptoms,
and may have needed antibiotics or other supportive therapy to clear the symptoms. These 3 viruses
have a zoonotic potential: there is a risk of human to non-human primate infection and minimal risk to
humans.
Conclusion
It is likely that the outbreak of respiratory disease based on available information at the time, was due
to an anthropozoonotic virus infection. A respiratory infection in humans, locals, researchers, field
assistants, may have been transmitted to the chimpanzees by unknown means.
Recommendations
Efforts to prevent disease spread from humans to chimpanzees should be reviewed. Any sick
people, including field staff, should not go to study or habituate the chimps, until they have fully
recovered, as they could very easily spread the respiratory or any other disease to the chimpanzees
which are often unexposed to the human diseases and therefore have little to no immunity to fight the
disease. The 7 m minimum distance between humans and chimpanzees should also continue to be
observed.
258 Appendices