Although Plasmodium knowlesi is a malaria that almost only affects Southeast Asian monkeys, new research published in the journal Nature Communications has found that the disease is very capable of developing in humans, according to NPR. Once rare, the human cases of "monkey malaria" have risen in both number and intensity over the past decade in Southeast Asia, especially Malaysia.
"We were really trying to understand whether what is normally thought to be a zoonotic disease — transmitted from animals to humans — is actually becoming something that is now transmitted between humans," study author Manoj Duraisingh said, according to NPR.
Scientists believe that the knowlesi parasites have figured out a way to adapt and better invade human red blood cells, something that it had difficulty with before due to the genetic split between humans and monkeys.
Monkey malaria is hardly new, as it dates back about 257,000 years, Motherboard reported.
The rise in knowlesi is most likely a result of deforestation, as monkeys and humans are now in closer quarters, NPR reported. Since the malaria is spread from mosquitoes biting an infected monkey and carrying the parasites, it's likely that more of these mosquitoes are now biting humans too.
Cases of knowlesi are now misdiagnosed, since its symptoms, such as a high fever, are now similar to the other four common human strains of malaria. In the past, monkey malaria used to cause milder symptoms in humans.
"There is growing concern that this simian parasite is adapting to infect humans more efficiently," Duraisingh and his co-authors wrote. The concerns may be warranted since according to NPR, hospitals in Malaysia Borneo have found more cases of knowlesi malaria than any other form.