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Mosquito Week 2022

Can we outsmart the world’s deadliest animal?

How humans are striking back against mosquitoes.


These mosquitoes are allies in the fight against dengue and other deadly viruses.


Losing a brother to the disease supercharged her fight against malaria.


Mosquitoes love blood, but did you know they have an even bigger sweet tooth?

Read the stories
This factory breeds 30 million mosquitoes per week. Here’s why.

Releasing Hope

These mosquitoes are allies in the fight against dengue and other deadly viruses.

Inside a two-story brick building in Medellín, Colombia, scientists work long hours in muggy labs breeding millions and millions of mosquitoes. They tend to the insects’ every need as they grow from larvae to pupae to adults, keeping the temperature just right and feeding them generous helpings of fishmeal, sugar, and, of course, blood.

Then, they release them across the country to breed with wild mosquitoes that can carry dengue and other viruses threatening to sicken and kill the population of Colombia.

This might sound the beginnings of a Hollywood writer’s horror film plot.

But it’s not.

This factory is real.

And the mosquitoes being released don’t terrorize the local population. Far from it. They’re actually helping to save and improve millions of lives.

Here’s how they do it: The mosquitoes being produced in this factory carry bacteria called Wolbachia that block them from transmitting dengue and other viruses, such as Zika, chikungunya and yellow fever, to humans. By releasing them to reproduce with wild mosquitoes, they spread the bacteria, reducing virus transmission and protecting millions of people from illnesses.

I’ve written before about these amazing Wolbachia mosquitoes, including last year when a new study showed how effective they could be in preventing diseases. The randomized controlled trial conducted in Yogyakarta, Indonesia, found that Wolbachia-carrying mosquitoes reduced the number of dengue cases in the city by 77 percent and dengue hospitalizations by 86 percent. In a new study in Medellín, dengue cases have declined by 89 percent since Wolbachia mosquitoes started being released in 2015.

These results are a huge breakthrough, offering proof that this new technology will protect entire cities and countries against the threat of mosquito-borne diseases. The World Mosquito Program, which is leading the Wolbachia effort, is now releasing these mosquitoes in 11 countries: Brazil, Colombia, Mexico, Indonesia, Sri Lanka, Vietnam, Australia, Fiji, Kiribati, New Caledonia, and Vanuatu.

And what’s remarkable about the Wolbachia mosquitoes is that once enough of them are released to offer disease protection, it’s a solution that’s self-sustaining. Over time, families will be spared the heartbreak of losing loved ones and communities won’t need to spend money on prevention and treatment for these mosquito-borne diseases, freeing up funds for other health priorities.

The World Mosquito Program aims to spread Wolbachia among Aedes aegypti mosquitoes, a tropical mosquito that is a host for dengue, yellow fever, and other viruses. (Malaria is spread through a parasite carried by the Anopheles mosquito and is not a focus of the Wolbachia effort.) With climate change, there is an urgency to the World Mosquito Program’s work. As global temperatures rise, Aedes aegypti mosquitoes, are finding more regions of the world habitable, increasing the spread of these diseases. The biggest risk is posed by dengue, which infects more than 400 million people each year and kills 20,000.

The demand for these lifesaving mosquitoes continues to grow and that means the World Mosquito Program needs to produce hundreds of millions of Wolbachia mosquitoes. That brings us back to the factory in Medellín, which is currently the world’s largest mosquito breeding facility in the world, producing more than 30 million mosquitoes per week. Other World Mosquito Program sites around the world are also breeding Wolbachia mosquitoes, but Colombia’s is currently the largest.

Hundreds of Wolbachia mosquitoes feed on blood at the World Mosquito Program facility in Medellín, Colombia. These mosquitoes will be released to mate with the wild mosquito population, spreading the Wolbachia bacteria that blocks the transmission of dengue and other mosquito-borne diseases to humans.

Until now, killing or repelling mosquitoes with insecticides, bed nets, and traps has been the priority, not mass producing them. As difficult as it is to kill mosquitoes, raising them by the millions may be even harder. Mosquitoes must be bred, fed, and housed under ideal conditions for them to grow and reproduce. The factory in Medellín has been perfecting the process and improving its efficiency so they can breed and release Wolbachia mosquitoes on a large scale.

The centerpiece of the mosquito factory is a colony of Wolbachia mosquitoes, called the brood stock, from which all future populations of Wolbachia mosquito offspring are bred. The brood stock offspring are then raised to create millions of eggs, which hatch when put in water and become larvae. Fed with fish meal, the larvae grow to become pupae, which then become adults. To thrive, adults need sugar (check out this story about how researchers in Zambia are exploiting mosquito’s craving for sugar to create a new bait that will control the spread of malaria) and blood, which the team sources from expired stocks at blood banks. 

Once the factory has bred millions of eggs and adult mosquitoes, they are ready to be released. The eggs are packaged in small gelatin capsules, each containing 300 eggs, which are given to residents to drop in water to hatch. The advantage of egg releases like this is that the eggs can easily be transported long distances and they can be hatched as needed.  The factory also releases adult mosquitoes by the thousands from the back of motorcycles roving the city. The World Mosquito team is also experimenting with releases from drones. The adult releases allow the Wolbachia mosquitoes to immediately begin mating with the wild mosquito population and spreading the virus-blocking bacteria.

It’s exciting to see how far the World Mosquito Program has come. Years ago, the idea of releasing mosquitoes as an ally in the fight against diseases struck many people as crazy. But support for this innovative solution has caught on in communities around the world. These amazing mosquitoes are taking flight and saving lives.

Malaria is deeply personal for this Kenyan scientist

True grit

Losing a brother to the disease supercharged her fight against malaria.

I know a lot of people who are driven to do something. When we were in high school, for example, Paul Allen and I would get quite absorbed in software projects—including neglecting sleep and showers. But that pales in comparison to the determination of Dr. Damaris Matoke-Muhia, a leader in the fight against malaria and other mosquito-borne diseases.

Damaris grew up in Birongo, Kenya, a rural village in the country’s western highlands. She showed remarkable talent in math and science from an early age, but she experienced discrimination at school and in her community because of her gender. Even some extended family members couldn’t understand why the family would “waste” (as they put it) precious resources on Damaris’s school fees, given that most girls in her village got married early or dropped out before completing secondary school.

Despite the social pressures, her father, who was a schoolteacher, was adamant that Damaris continue her studies. After Damaris graduated from secondary school, her father sold cows and a plot of land to pay for her tuition at the University of Mysore, in India. But he could afford to send her only $50 every three months for rent and living expenses. So five days a week, Damaris walked more than 15 miles to the university and back, and she barely ate enough to survive. “If I couldn’t eat a meal at a friend’s house, I would often go two days without eating,” she says. “But I refused to break, and I never missed a class.” She entered university weighing about 150 pounds, and when she finished her studies in India, she was down to only 90 pounds. Many neighbors assumed she had contracted HIV/AIDS. “They ridiculed my father. They said, ‘You spent all that money, and now she comes home to die.’”

On top of deprivation, Damaris suffered a huge loss while she was studying in India. She was 23 and working on a master’s degree in biotechnology when her younger brother Abel, also a gifted science student, died of an especially dangerous form of malaria. Damaris couldn’t afford a ticket home for the funeral services.

Abel’s death had a profound effect on Damaris’s life, giving her clarity on how she would use the education for which she and her parents had sacrificed. “For the first time, I knew my education was not a mistake or a waste,” she explains. “I knew I could play a role in eliminating malaria in my home country.”

After returning to Kenya, Damaris took on an almost-impossible load again. While pursuing a doctorate in molecular medicine, she also worked full time as a research officer at the Kenya Medical Research Institute (KEMRI) so she would have money to help put her seven surviving siblings—including three girls—through university. Thanks to her support, all seven earned undergraduate degrees, and two went on to complete post-graduate degrees as well.

Today, Dr. Damaris Matoke-Muhia is Principal Research Scientist at KEMRI and is manager for the Capacity Building, Gender Mainstreaming, and Career Progression program at the Pan-African Mosquito Control Association. In the field, she traps mosquitoes to study their behavior and learn how they develop insecticide resistance. In the lab, she is researching new techniques to counter this resistance and specific innovations to control malaria. In villages across Kenya, she surveys breeding sites, investigates the effectiveness of preventive tools, conducts health education for families, and screens for malaria infections. On the international level, she is helping women rise to leadership positions in the fight against malaria and other mosquito-borne diseases.

Dr. Damaris Matoke-Muhia and her colleague work in the lab researching new ways to combat mosquitoes and insecticide resistance management to reduce transmission of malaria and save lives.

Dr. Damaris Matoke-Muhia walks with her colleague, Rukiya Haji, at the Kenya Medical Research Institute in Nairobi, Kenya.

Dr. Damaris Matoke-Muhia and her colleague work in the lab researching new ways to combat mosquitoes and insecticide resistance management to reduce transmission of malaria and save lives.

Dr. Damaris Matoke-Muhia walks with her colleague, Rukiya Haji, at the Kenya Medical Research Institute in Nairobi, Kenya.

Her focus on women is not just a function of the gender discrimination she faces to this day. It’s also driven by the knowledge that the world has been trying to fight malaria with one hand tied behind its back.

Research demonstrates that men hold 75 percent of all leadership positions in global health—even though women perform 70 percent of all healthcare services worldwide and, perhaps even more important, hold the key to implementing effective malaria control measures at the household level. “Women are clearly in charge in the villages I travel to for field work,” Damaris says.

This is why our foundation is supporting Damaris’s work to open the doors to women in community-level initiatives and senior positions in international health organizations. As Damaris says, “If we’re serious about malaria elimination in Africa, women must help develop, design, deliver, and implement strategies that take account of the reality that women are in charge of ensuring things go well at the household level.”

Damaris and her colleagues have researched the major obstacles that make it hard for women to take top leadership roles, and now they’re addressing each one. For example, they are providing leadership training to women in science, helping rising leaders find mentors, and advocating for workplace policies that support women.

Damaris offers multiple reasons for optimism. For example, she will soon be able to use her networks of women leaders to help deploy RTS,S—the world’s first malaria vaccine. Other effective control measures include improved insecticide-treated bed nets and attractive targeted sugar baits. In combination, these new tools will prevent tens of thousands of children from getting malaria each year. They will also help free mothers to focus on things other than taking care of family members suffering with malaria—giving a big boost to their productivity at home and in the workplace.

Her greatest source of optimism is her own children. In addition to having a 10-month-old son, she and her husband have two daughters, ages 13 and 10, who are outstanding science students and want to pursue health as a career. Their older daughter, Amirah, wants to be a neonatologist. Their younger daughter, Anabel, wants to be a veterinarian. Thanks to their parents and their community of friends in Nairobi, neither girl sees any reason to limit her dreams.

Meet more of my heroes in the field

Sugar Fix

Sweet dreams

Mosquitoes love blood, but did you know they have an even bigger sweet tooth?

Everyone knows mosquitoes have a taste for blood, but did you know they have an even bigger sweet tooth?

Mosquitoes love sugar.

Just as humans are drawn to the sweet smell of a chocolate shop or bakery, mosquitoes find the smell of sugar irresistible.

All mosquitoes need sugar to survive. Female mosquitoes consume blood to lay eggs, but both male and female mosquitoes require sugar for energy. In fact, even though mosquitoes buzzing in your ears may appear single-minded about biting you, they need sugar more often than they need blood.

Exploiting this craving, researchers have developed a lethal new tool to kill mosquitoes and protect people living in areas at high risk for malaria and other mosquito-borne diseases.

Here’s how it works: In nature, mosquitoes get sugar from flower nectar and plants. But scientists have developed a tempting bait that lures mosquitoes with a highly attractive fruit scent. When they land on it to get their sugar fix, the mosquitoes begin feasting on a sweet meal laced with insecticide. Not long after, they drop dead, reducing mosquito populations and, researchers hope, the spread of malaria in the communities where the traps are used.

While other insects, like bees and butterflies, may also be drawn to the bait’s sweet scent, the bait is just lethal for mosquitoes. A protective membrane, only accessible to mosquitoes, covers the bait and prevents other insects from feasting on the deadly meal inside.

This new mosquito control tool, called Attractive Targeted Sugar Baits or ATSBs, developed by Westham Co., is simple to use, affordable, and has the potential to be a game changer in the effort to eradicate malaria.

And it couldn’t arrive soon enough.

Over the past two decades, the world has dramatically reduced the global burden of malaria, preventing 1.7 billion cases and saving 10.6 million lives. This progress has been attributed, in large part, to the widescale use of long-lasting insecticide-treated bed nets, which protect people from bites while they sleep, and indoor residual spraying, which kills mosquitoes that land on insecticide-treated walls and ceilings in homes.

As effective as these tools have been, both mosquitoes and the malaria parasite are constantly evolving, sometimes making these interventions less effective. We’ve seen this again and again with resistance to insecticides and malaria drugs. And that’s why it’s critical that the world continues to innovate with new ways to prevent the spread of malaria.

In response to the widespread use of bed nets and indoor insecticide spraying, mosquitoes have changed their behaviors, according to some researchers. In some areas, instead of seeking their blood meals only inside homes after bedtime, malaria-carrying mosquitoes are now biting outside homes, and earlier in the evening, when people will often cook and socialize.

And this is how the sugar baits fit in.

By attracting mosquitoes outside, sugar baits offer a highly effective mosquito control tool for households. About the size of a sheet of notebook paper, sugar baits can be easily installed with a hammer and a nail. Two baits hung on the adjacent outside walls of a home are enough to offer months of protection.

In studies conducted in Mali in 2016 and 2017 researchers found that the sugar baits dramatically reduced mosquito populations and malaria cases in the communities where they were used.

A more recent modeling analysis predicted that sugar baits, when used to complement long-lasting insecticide-treated bed nets and indoor spraying, could reduce malaria cases by 30 percent in areas with high malaria burdens.

In 2020, there were an estimated 241 million malaria cases. A 30 percent reduction in malaria cases would be a huge breakthrough and save many lives.

That’s why our foundation has been supporting the development of sugar baits, including sponsoring a large-scale field trial currently underway in Kenya, Mali, and Zambia. So far, the results have confirmed the effectiveness of the bait stations.

If all goes well with the trials, sugar baits could be available for widespread use as soon as next year.

No need to sugarcoat it. For the millions of people at risk of malaria around the world, that would be welcome news.