The outbreak of dengue fever that has unfolded in Latin America over the previous three months is staggering in its scale — one million instances in Brazil in a matter of weeks, an enormous spike in Argentina, a state of emergency declared in Peru and now one other in Puerto Rico.

It forewarns of a altering panorama for the illness. The mosquitoes that unfold dengue thrive in densely populated cities with weak infrastructure, and in hotter and wetter environments — the kind of habitat that’s increasing shortly with local weather change.

Greater than 3.5 million instances of dengue have been confirmed by governments in Latin America within the first three months of 2024, in contrast with 4.5 million in all of 2023. There have been greater than 1,000 deaths to this point this yr. The Pan-American Well being Group is warning that this can be the worst yr for dengue ever recorded.

The quickly shifting illness panorama wants new options, and researchers in Brazil delivered the lone shred of excellent information on this story with the latest announcement {that a} medical trial of a brand new dengue vaccine, delivered in a single shot, had supplied sturdy safety towards the illness.

There are two current vaccines for dengue, however one is an costly two-shot routine, whereas the opposite could be given solely to individuals who have already had a dengue an infection.

The brand new one-shot vaccine makes use of stay, weakened types of all 4 strains of the dengue virus. It was created by scientists on the Nationwide Institutes of Well being in the USA and licensed for improvement by the Instituto Butantan, an enormous public analysis institute in São Paulo.

Butantan will make the vaccine. It already produces many of the immunizations utilized in Brazil, and has the capability to make tens of thousands and thousands of doses of this new one. The institute plans to submit the dengue vaccine to Brazil’s regulatory company for approval within the subsequent few months and will start producing it subsequent yr.

However that gained’t assist with this outbreak and, by the point the manufacturing gears up and a nationwide rollout will get began, it might not be sufficient to assist with the subsequent one, both; dengue usually surges in three- or four-year cycles.

And it gained’t essentially be of assist to the remainder of Latin America: Butantan will solely make the vaccine for Brazil. The multinational drug firm Merck & Co., which additionally licensed the NIH expertise, is growing a associated vaccine which can be bought in the remainder of the world; the efficacy of that vaccine has not but been examined in a medical trial.

And there may be, after all, demand for a dengue vaccine past the Americas: Mosquitoes are spreading the illness to Croatia, Italy, California and different areas that haven’t seen it earlier than. Locations used to dealing with gentle outbreaks now face record-breaking ones: Bangladesh had 300,000 instances final yr.

Dengue is usually identified by the title breakbone fever, after the excruciating joint ache it causes. Not everyone experiences that ache: Three-quarters of individuals contaminated with dengue don’t have any signs in any respect, and amongst those that do, most instances resemble solely a light flu.

However about 5 % of people that turn out to be sick will progress to what’s known as extreme dengue. Plasma, the protein-rich fluid element of blood, can begin to leak out of blood vessels, inflicting sufferers to enter shock or have organ failure.

When sufferers with extreme dengue are handled with blood transfusions and intravenous fluids, the mortality charge tends to be between 2 and 5 %. However once they don’t get therapy — as a result of they don’t notice it’s dengue and don’t search therapy shortly sufficient, or as a result of well being facilities are overwhelmed — the mortality charge is 15 %.

In Brazil, the present dengue outbreak is hitting kids hardest; these underneath 5 have the very best mortality charge of any age group, adopted by these age 5 to 9. Adolescents between 10 and 14 have the very best variety of confirmed instances, in accordance with the Instituto Oswaldo Cruz, a nationwide public well being analysis heart.

As clinics started to be overwhelmed with dengue sufferers in January, the Brazilian authorities purchased the complete international inventory of a Japanese-made vaccine for dengue known as Qdenga. Public well being nurses are delivering it to kids ages 6 to 16, however there can be sufficient vaccine to completely vaccinate solely 3.3 million of Brazil’s 220 million individuals this yr.

This large nationwide effort will shield a couple of million kids, but it surely gained’t contribute something to its herd immunity.

Qdenga is just not low-cost: It’s about $115 per dose in Europe and $40 in Indonesia. Brazil is paying $19 per dose, having negotiated a cheaper price for its big buy.

Takeda Prescription drugs, which makes Qdenga, introduced a deal final month with Organic E, a big Indian generic drug maker, to license and produce as much as 50 million doses a yr, a part of a race to speed up manufacturing. The Indian vaccine ought to price significantly much less. However Organic E is unlikely to have regulatory approval to promote it earlier than 2030; it’s a sluggish course of that includes transferring expertise, establishing a manufacturing line and getting a brand new model of even a widely known product accepted by regulators.

Dengue prices Brazil a minimum of $1 billion a yr in well being care therapy and misplaced productiveness. And that determine doesn’t take note of the human struggling concerned.

The truth that there are 4 completely different strains of the dengue virus complicates greater than the method of creating a vaccine: The doubtless deadly type of the illness is extra frequent when sufferers have a second an infection, with a unique pressure than they’d the primary time. Qdenga protects towards all 4 strains of dengue, and the hope is that the brand new Butantan vaccine does, too, though the information launched to this point exhibits it examined towards solely the 2 varieties that had been circulating through the first a part of the trial; extra outcomes are anticipated in June.

Thousands and thousands extra individuals can have been uncovered to dengue when this outbreak lastly passes. However they’re going to want that new vaccine extra urgently than ever.