Researchers reviewed 39 existing studies to understand how common yellow fever virus is in monkeys and other non-human primates. They looked at data from over 7,000 animals, mostly from the Americas, particularly Brazil. The goal was to see how often the virus was detected in these animals, which can act as early warning signs for human outbreaks.
The review found the virus was present in many of the animals tested. When using a test called RT-PCR, about 31% of samples were positive. When using a different test on tissue samples, about 43% were positive. Howler monkeys and titi monkeys seemed to have the highest rates of infection. In the 19 individual cases described in detail, all of the infected animals died, with severe liver and other organ damage.
It's important to be careful with these results. The studies included were very different from each other, which makes it hard to get a single, precise number. Also, most of the data came from the Americas, with very little from Africa, where yellow fever is also common. This means the findings might not apply everywhere. The study shows that monitoring monkeys is a key part of a 'One Health' approach to tracking diseases that can spread between animals and people.
