Nipah and Hendra viruses can infect humans through fruit eaten by an infected fruit bat

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Two deadly bat-borne viruses with no known cure could be treated with a well-known and widely available antimalarial drug, researchers have found.

If the success of laboratory tests — which showed that chloroquine renders the related Nipah and Hendra viruses non-infectious — is repeated in animals the drug could be used almost immediately as it has already been through safety testing and is widely available, say researchers.

Nipah and Hendra are both emerging public health concerns in parts of South Asia and Australia respectively. They infect humans either through fruit eaten by an infected fruit bat, or through close contact with pigs.

Anne Moscona of the Weill Medical College of Cornell University and colleagues screened 23,000 compounds for their ability to block different stages of the viral life cycle — entry into the cell, multiplication, exit, and infection of new cells.

Chloroquine effectively blocked infection by interfering with a protein crucial to the viruses' ability to infect new cells. "Viruses get in and then viruses get out, but then those viruses that come out are not infectious," explains Moscona, whose research was published last week (4 March) in the Journal of Virology. 

The findings are yet to be confirmed with animal tests, cautions Moscona. "But the fact is that it works very well in vitro. It works so well that the virus is completely inhibited at concentrations people are on for malaria prophylaxis."

Pierre Rollin, a virologist and chief of Disease Assessment at the Special Pathogen Branch of the U.S Center for Disease Control and Prevention says that if the infection is detected early on, before the onset of neurological symptoms, then chloroquine is likely to work well.

But the virus has often infected the brain by the time people go to clinicians, particularly in remote parts of Bangladesh. Researchers don't know whether chloroquine can enter the brain, and stop the neurological infection, he says.

Still, "It's a big progress," according to Rollin. "Let's say you have several cases occur in an area," he says. Even if the first few patients were to die from the disease, "maybe you can treat the family members with the drug and protect them".

Link to abstract in the Journal of Virology