A new virus, named the Kiwira virus, has been found in several free-tailed bats across the Eastern and Central African countries of Tanzania and the Democratic Republic of the Congo. While there’s no evidence yet of any serious threat to humans, the researchers have called for follow-up studies among bats in the region in order to better understand the biology and distribution of this and similar viruses in Africa.
Kiwira virus is a type of hantavirus, a virus family usually found in rodents and spread to humans via aerosolization of infected urine, feces, and saliva. How serious the disease is once it gets inside a human host depends heavily on what type of hantavirus it is. Sin Nombre virus, for example, is a hantavirus spread by deer mice in the USA with a mortality rate of more than one in three. On the other hand, there’s Puumala virus, a hantavirus common across Europe caused by bank voles: while this can cause hemorrhagic fever and severe kidney problems, its actual mortality rate is less than one in 200.
This raises the question of just how worried we should be about Kiwira virus – and in that respect, we have both good news and bad news. The problem is, we simply don’t know how dangerous Kiwira virus might be in a human host. However, the reason for that knowledge gap may be reassuring: it’s that so far, there has never been any evidence that bat-borne hantaviruses can even infect humans.
In fact, there’s not all that much evidence for hantaviruses being a problem for bats, either. The number of the little flappy fellas found to be carrying Kiwira virus numbered only six out of 334 bats from Tanzania, and just one out of 49 bats from DRC. That’s a pattern that holds for nearly all bat-borne hantaviruses across the continent: they’ve generally been found in a few individuals, rather than entire populations of the animals.
That said, the authors point out that “hantavirus disease often manifests as a febrile illness with non-specific symptoms […] and might be easily overlooked.” In other words, hantaviruses (and Kiwira virus in particular) may well be infecting humans already, but causing such generic symptoms that nobody has really noticed yet.
Add to that the fact that the bats in the study were all found and captured close to human settlements, and the threat level becomes non-negligible. That proximity has actually been suggested as one reason why so many novel zoonotic diseases stem from bats: “it's pretty common in other parts of the world to live close to bats,” explained Chelsea Wood, an assistant professor of parasite ecology at the University of Washington, in National Geographic last year. In some countries, she said, bats are “as common there as squirrels are here,” with children playing near the animals’ habitats, and adults hunting and eating them.
“The scary thing about these zoonotic viruses is that the spillover process is happening all the time,” Wood said. “COVID-19 is a great example.”
The results can be found in the journal Viruses.