How Wolbachia bacteria could help us tackle some of the world’s most neglected tropical diseases

The animals that pose the biggest threat to humans are not lions, sharks, or snakes; they are tiny mosquitoes. Mosquitoes kill more than 600,000 people every year from malaria alone, but they also carry and spread a host of other tropical diseases.

One of those is dengue fever. It’s a common disease found in the tropics and subtropics, and around 60 million recorded cases occur each year.

For most people, the symptoms of dengue fever are extremely unpleasant: a fever, severe headache, nausea, joint and muscle pain, and sometimes a rash. Some die from it. Around 25,000 people die from dengue each year, almost all of them in Asia. To put this in perspective, in most years over the past decade, fewer than 25,000 people died globally in all natural disasters combined.¹ Ending dengue fever would be like ending the death toll from floods, wildfires, hurricanes, and other disasters.

Unlike some other tropical diseases, dengue fever has no specific antiviral treatment, and while vaccines exist, none provide universal protection comparable to vaccines for diseases like measles or polio.

However, one promising solution could dramatically reduce the spread of infections and the number of people experiencing a severe form of the disease: the Wolbachia method.

Wolbachia is a tiny bacterium that naturally occurs in around half of all insect species, including fruit flies, bees, beetles, moths, dragonflies, butterflies, and some mosquitoes.

In this article, I’ll focus on how Wolbachia can be used against dengue fever. I’ll examine how this innovative new method works, how effective it is in reducing transmission, and how it can be rolled out across the tropics to protect as many people as possible.

To understand how Wolbachia could stop the spread of disease, we must first understand how mosquitoes transmit them. Mosquitoes do not carry these tropical diseases naturally. Instead, female mosquitoes can pick up the virus when they bite someone already infected with dengue fever, yellow fever, or Zika. When they then bite their next victim, they can pass it on.

The spread is from human to human, but mosquitoes act as the messenger.

The Wolbachia method works because it stops the viral infection from developing in the mosquito. It boosts its immune system, and since mosquitoes need resources to survive, it reduces the available resources (such as cholesterol) that viruses need to grow. Wolbachia makes it much harder for viruses to thrive, and if they’re not present in the mosquito, they can’t be passed on to the next human.

But how do scientists develop a whole population of Wolbachia-positive mosquitoes?

First, they extract Wolbachia bacteria from insects that naturally carry them. Around half of insects do, so we’re never in short supply. Then, under a microscope, they inject these bacteria into Aedes aegypti embryos. This is an incredibly delicate process that requires very fine needles and lots of expertise. Even then, many of the embryos don’t survive. Those that do, though, are raised into adult mosquitoes.

The second step is to develop a colony of Wolbachia-positive mosquitoes in the lab. This is done by taking the females with Wolbachia and having them mate with male mosquitoes. Wolbachia is passed on not only to males but also to mosquito offspring that the females produce.

Once a big enough population of Wolbachia-carrying mosquitoes has been established, they’re released into the wild, where they mix with natural populations. This part of the process can require large teams of volunteers. In their lifetimes, mosquitoes usually don’t fly more than 150 meters from where they hatch, so you need many spaced releases to cover an area that’s even just a few tens of square kilometers. Over several generations — typically within three to six months — more and more mosquitoes within the local environment become “Wolbachia-positive” until almost all of the mosquitoes carry the bacteria. That means they do not carry or transmit viruses like dengue fever to humans.

In the chart below, I summarized this process.

This method tends to be self-sustaining, so once a successful “release” of mosquitoes has occurred, it doesn’t need to be repeated.

The method does not involve genetic modification of mosquito species; it simply relies on a natural bacterium that’s extremely common among insects and many other mosquito species. Humans are exposed to these bacteria daily through the food they eat and the insects that bite them. There have been no reported health risks associated with exposure to it.

Many things should work in theory; the question is whether they also work in practice. How about the Wolbachia method?

One of the most famous trials was conducted by the World Mosquito Program in Yogyakarta, a city in Indonesia that is badly affected by dengue fever and other neglected tropical diseases.² Working with the local community — a population of around 310,000 people — the study site was split into 24 areas, each measuring around one square kilometer.

The results are staggering. Wolbachia reduced dengue fever’s incidence (the number of new infections) by 77%, and the number of dengue hospitalizations was 86% lower in the areas with Wolbachia treatment. The figure below summarizes these results.

We can also see this effect when comparing dengue fever infection rates over time. In the chart below, we can see dengue fever cases in areas that received the Wolbachia treatment as the solid red line and those that didn’t get the treatment as the blue line. In the period before the Wolbachia release in 2016, all of these areas experienced large outbreaks at similar times. But after the deployment of Wolbachia (the shaded zone at the end), the areas with the treatment had significantly lower levels than those without. That suggests that it was effective in reducing the spread of the virus.

But as you can see in the chart, even in areas with the Wolbachia treatment, the number of dengue fever infections didn’t drop to zero. That’s why combining it with other control methods, such as effective vaccines, sprays, and bednets, might still be needed to ensure everyone is protected. These other interventions would be required at a much lower scale than in a scenario without any Wolbachia treatment, and the results would be far better than what could be achieved with sprays or nets alone.

Indonesia is not the only country where we have evidence that this method works.

The first Wolbachia releases by the World Mosquito Program were in Northern Queensland, Australia, back in 2011. Over the last 14 years, monitoring has shown that Wolbachia-positive mosquitoes continue to self-sustain. There are no signs of local dengue transmission in the areas with the highest rollout. As Dr Richard Gair, a physician in the local area, put it:

“Far North Queensland is now essentially a dengue-free area for the first time in well over 100 years.”

Programs in Brazil and Colombia reduced new dengue infections by more than two-thirds, and in some cases, more than 90% in the areas where they were released. In Brazil, the same method also led to a substantial decline in the incidence of the Zika virus and chikungunya.³

These results seem too good to be true. The Wolbachia method has been shown to dramatically reduce the spread of not just dengue fever but also other neglected diseases. Wolbachia is self-sustaining, unlike other management tools such as vaccines, mosquito sprays, or bednets, which must be readministered or delivered periodically. Once Wolbachia-positive mosquito populations have been established, they remain so for long periods. There are no obvious biodiversity concerns, and this method does not involve genetic modification (which often receives public and political pushback and involves additional regulatory hurdles).

What’s stopping them from being scaled across much of the tropics, where tens of millions of people are affected by these diseases every year?

The first potential barrier is public and political acceptance. In each trial program, researchers invested heavily in community engagement through local media and key stakeholders to explain to the local population what was involved, how it worked, and the impacts. People could share their concerns and have their questions answered. This was particularly successful in building community trust, and support for the trials was high. In Yogyakarta, public acceptance was at 88%, and in other parts of Indonesia where interventions took place, this was over 90%. In Colombia, Australia, and Brazil, levels of support were similarly high.

These trials were clearly carefully planned and small enough to develop public trust. This might be harder if they were to be rolled out across much larger areas. However, the difficulty in building confidence in these initial trials is that these Wolbachia programs were extremely new and experimental to some extent. As Wolbachia became more common and the benefits were more widely known, the amount of engagement needed to help locals understand the costs and benefits would fall. I expect this will not be a blocker, and will be more welcome to many than alternative health measures such as vaccines or chemical sprays.

The challenge of funding these programs is a bigger barrier. Most initial programs have been financed through institutional grants or philanthropic donations.⁴ These financial commitments are viable at the trial stage, but generous donations will not be sufficient to scale these programs across the tropics. Other forms of finance — most likely government funding in each country — will be needed for this next stage.

The Wolbachia method requires a substantial upfront cost to breed or buy mosquitoes and develop labor-intensive release programs. But the “running” costs are very low once they’ve been deployed. Only a few studies are looking at the cost-effectiveness of Wolbachia, but early evidence suggests a payback of $1.35 to $3.40 for every dollar spent.⁵ A study looking at the cost-effectiveness of Wolbachia programs in a densely-populated city in Indonesia estimated that it cost around $1500 to prevent one disability-adjusted life year (DALY), a measure of disease burden. By global health standards, that is relatively cheap, especially in middle-income countries where many incredibly cheap life-saving interventions, such as childhood vaccinations, are already widely used. So these programs — particularly in areas with a lot of dengue fever — should pay themselves back and be a good investment for most governments, but that doesn’t mean securing the capital costs is easy.

In the future, countries would either have to develop their own mosquito-breeding factories or import mosquito eggs internationally, which also introduces challenges around preservation, risks of infection, and biosafety concerns.

The last logistical hurdle is distribution. In the trials, mosquitoes were released every 50 meters. They therefore relied on a large number of program staff and community volunteers. Scaling this across large cities efficiently and sustainably is a challenge. There is an opportunity for emerging technologies, such as drones, to make this process less labor-intensive and more optimized, but these solutions are still at the trial stage.

The Wolbachia method is an extremely promising solution that could protect hundreds of millions of people from some of the world’s most neglected diseases, which currently have no cure.

Hannah Ritchie (2025) - “How Wolbachia bacteria could help us tackle some of the world’s most neglected tropical diseases” Published online at OurWorldinData.org. Retrieved from: 'https://ourworldindata.org/wolbachia-neglected-tropical-diseases' [Online Resource]

@article{owid-wolbachia-neglected-tropical-diseases,
    author = {Hannah Ritchie},
    title = {How Wolbachia bacteria could help us tackle some of the world’s most neglected tropical diseases},
    journal = {Our World in Data},
    year = {2025},
    note = {https://ourworldindata.org/wolbachia-neglected-tropical-diseases}
}

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