AILSA CHANG, HOST:
The chikungunya virus is on the rise again, including in South America, where more than a quarter million new cases have already surfaced this year. The disease is rarely fatal, but it can leave long-lasting joint pain. As NPR's Ari Daniel reports, a vaccine may soon be on the way.
ARI DANIEL, BYLINE: Over the years, Dr. Susana Lloveras has seen cases of chikungunya in Buenos Aires, where she works as an infectious disease physician at Hospital Muniz.
SUSANA LLOVERAS: But it is not common for us - no more than one or two cases.
DANIEL: Each year, and always from people bringing the mosquito-borne virus with them from other countries. But earlier this year...
LLOVERAS: We receive everyday patients with chikungunya.
DANIEL: Including some with no travel history, which means, for the first time, mosquitoes within Buenos Aires were transmitting the disease. Case counts are up across Argentina. When someone enters Lloveras' hospital with chikungunya, there's no mistaking it.
LLOVERAS: The patients came here with fever and with pain in their joints.
DANIEL: The joints in their hands and feet, says Lloveras, and their knees. The pain can get so bad that some have difficulty walking or even holding a cup of coffee.
LLOVERAS: You are well, and suddenly, you can't move. You need another person help you to do the common task of everyday.
DANIEL: Lloveras prescribes medicine to ease the fever and pain. But she tells her patients the disease just has to run its course, which can be challenging because some people suffer from the joint pain for months or years even though their immune systems have created antibodies to clear the virus.
MARGARET KIELIAN: We don't really understand what causes that debilitating arthritis.
DANIEL: Margaret Kielian is a virologist at the Albert Einstein College of Medicine, and she and her colleagues found something that could bring us a step closer to solving this mystery. So most viruses make us sick by turning ourselves into virus-making machines. They released loads of new viral particles that can go on to infect new cells. Chikungunya does that, but it also does something else.
KIELIAN: The virus induces the infected cell to generate these very dramatic long extensions that can go from the infected cell to neighboring cells.
DANIEL: One or two tendrils, sometimes as long as the cell itself, snaking outwards - at times toward uninfected cells. And even though these tendrils might be bathed in antibodies...
KIELIAN: That contact between the infected cell and the uninfected cell shields the virus from the antibodies, and that's how that cell gets infected.
DANIEL: That is, the virus can spread through these extensions between cells, escaping attack by the immune system.
KIELIAN: It's early days, but it suggests this might be one mechanism by which the virus can sort of get established - maybe in joint tissues. That may be important in causing the arthritis. We'll see.
DANIEL: This study, which was conducted in mice, was published in the journal Nature Microbiology.
NISCHAY MISHRA: This information is very useful.
DANIEL: Useful to inform the development of vaccines for a disease whose footprint is growing, says Nischay Mishra. He's a virologist at Columbia University who wasn't involved in the study.
MISHRA: It's a global concern. Like, the way climate is changing, there are more chances, like, mosquitoes can survive everywhere.
DANIEL: Chikungunya's already a problem in places like India, China and numerous countries in Africa. Even in the U.S., Texas and Florida have, in previous years, reported local transmission of the disease. Fortunately, several vaccine efforts are underway, and Mishra says one may be approved as soon as the end of this year.
Ari Daniel, NPR News.
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