A children’s ward for dengue fever in Bangladesh’s capital.bdul Goni/AFP/Getty via Vox

This story was originally published by Vox and is reproduced here as part of the Climate Desk collaboration.

There’s a reason dengue infections are also called “breakbone fever.”

Along with a mild fever, symptoms of the mosquito-borne illness include bone-deep, aching pain in the joints and behind the eyes. In severe cases, blood vessels begin to leak. And in the worst cases, that can lead to organ failure.

More than 14 million people contracted dengue last year, and the real number is likely several times higher. While it remains most common in South Asia and Latin America, it’s no longer just a tropical disease. Warming temperatures are pushing dengue into southern Europe and the United States. Last year, Texas saw its highest case count in two decades, including locally acquired infections, meaning the virus is now circulating here, not just arriving with travelers.

The public health tools we have—the dengue vaccines, bed nets, fogging campaigns, public awareness to drain standing water—are all aimed at keeping mosquitos at bay and preventing infections in the first place. There’s nothing for after: no antivirals—nothing like Paxlovid for Covid, or Tamiflu for the flu, or artemisinin for malaria. Once you’re sick, the strategy is just supportive care and hope.

Earlier this month, though, that changed.

A new antiviral pill for dengue called mosnodenvir showed promising results in early phase 2 trials. In a study where volunteers were deliberately exposed to dengue, roughly half of those who received the highest dose never got sick at all. For a field that has struggled for decades to find an effective antiviral, it’s the clearest evidence yet that a drug can prevent dengue—and researchers believe the same pill could eventually treat people who are already infected.

But, even before the results were published, Johnson & Johnson, the American pharmaceutical giant that developed mosnodenvir, had already abandoned any efforts to bring the drug to market.

Last year J&J announced it would wind down its dengue antiviral work, with a “strategic reprioritization” of its research toward non-communicable diseases like cancer and obesity. What this means is that one of the most promising dengue drugs ever tested is now without a pharma sponsor, waiting for someone else to carry it forward.

André Siqueira, who heads the dengue program at the Drugs for Neglected Diseases Initiative (DNDi), said........

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