While the public’s nervous obsession with Zika may be over, medical researchers still have questions. Can the virus survive in a nonhuman host? Can the blood of that nonhuman host infect others? For researchers at the National Primate Research Centers, it’s questions like these that drive their curiosity and compel them to find answers.

Scientists at the Wisconsin National Primate Research Center wanted to know if a mosquito bite can turn a nonhuman mammal into a virus carrier. To investigate this, they let Zika-carrying mosquitoes infect rhesus macaques. They then compared those monkeys and their symptoms to macaques that the researchers had injected with Zika.

The differences were small but significant. “It’s a difference of a couple days to what we call peak viremia,” says Dawn Dudley, a UW-Madison pathologist. Viremia is the medical term for when the virus enters the bloodstream. At that point, it can migrate from the spot of initial contact to other regions of the body where it may lie dormant, waiting to be passed on to someone or something else.

It’s unclear why the virus moves slower when delivered through a mosquito bite. “The biology of the disease probably depends a lot on how the mosquitoes transmit that disease – mechanically how they do it, and biologically what comes along with the virus when the mosquito bites,” says Tom Friedrich, a UW-Madison professor of pathobiological sciences.

The virus was also less likely to affect the central nervous system tissues of mosquito-bitten macaques.

Despite these differences, the virus never became strong enough to infect mosquitoes who fed on the macaques. “But that doesn’t mean other nonhuman primates couldn’t do that,” says Dudley. And with more questions, there’s always more research.

Reviewed August 2019