A longshot technology first bankrolled by Bill Gates more than a decade ago has shown so much promise against the Zika virus that the tech billionaire is now helping fast-track its use in Brazil and Colombia.

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A longshot technology first bankrolled by Bill Gates more than a decade ago has shown so much promise against the Zika virus that the tech billionaire is now helping fast-track its use in Brazil and Colombia.

The method, which sounds more like science fiction than traditional disease control, involves infecting mosquitoes with bacteria that prevent the bloodsuckers from transmitting Zika to people.

“It’s really a novel paradigm,” said Steve Kern, deputy director of quantitative sciences at The Bill & Melinda Gates Foundation.

The Seattle philanthropy announced Wednesday that it is joining the U.S. and British governments and the Wellcome Trust to provide $18 million for field trials in the sprawling cities of Rio de Janeiro and Medellin.

If the approach works as well as it has in smaller trials, it could be cheaper and more effective than using insecticides to reduce the risk of Zika and related diseases, like dengue fever, Kern said.

Researchers had already been testing the method against dengue in South America when the Zika epidemic exploded, said Scott O’Neill, the Australian entomologist who originally pitched the unconventional idea to Gates. The new funding is part of an emergency response to scale those tests up quickly, after laboratory studies found the bacteria might also block transmission of Zika.

“Zika is a really scary thing,” O’Neill said. “It can be benign in many people, and yet so devastating to pregnant women.”

His approach to fighting mosquito-borne diseases seems counterintuitive — at first.

Instead of trying to reduce the population of Aedes aegypti mosquitoes, which transmit both Zika and dengue, O’Neill and his colleagues enlist local residents to release more mosquitoes into their neighborhoods.

These “good” mosquitoes are infected with a naturally occurring bacterium called Wolbachia (wol-bock-ee-uh), which prevents Zika and related viruses from proliferating inside the mosquitoes. Initial tests in Australia showed Wolbachia spreads quickly through mosquito populations, so that within a few weeks all of the mosquitoes in the immediate vicinity appear to carry the infection.

O’Neill, a professor at Monash University in Australia, hit on the idea of harnessing Wolbachia in the 1990s. His target was the dengue virus, which kills more than 11,000 people a year and sickens nearly 60 million.

When the Gates Foundation issued a call in 2003 for innovative research ideas to address what the foundation called Grand Challenges in Global Health, O’Neill submitted a proposal, even though he wasn’t sure he would be able to deliver on his own ambitious goals.

“I thought the probability of success was probably less than 50 percent,” he recalled.

Out of more than 1,500 proposals, his was one of 43 selected. With a $7 million initial grant, he launched the program now called Eliminate Dengue.

Several early breakthroughs helped propel the research, including development of a technique to insert Wolbachia into the eggs of Aedes aegypti, which doesn’t normally carry the bacteria. The project has received about $40 million from the Gates Foundation since its inception, and is one of only a handful of original Grand Challenges projects still standing.

So far, O’Neill and his team have conducted field tests in five countries, including Vietnam and Indonesia.

In all cases, local communities embraced the project.

The fact that Wolbachia is already present in about 60 percent of insect species, and doesn’t pose a danger to humans, helped allay fears, O’Neill said. The technique also doesn’t involve genetic engineering.

The “good” mosquitoes are delivered in large buckets or Chinese takeout-style boxes seeded with dried mosquito eggs. Residents add water, and wait for the eggs to hatch, Kern explained.

“It’s basically getting the neighborhood to agree: We will put these Chinese noodle boxes in our backyards and essentially replace the bad mosquitoes … with the good mosquitoes over time,” he said.

Preliminary data show that dengue transmission plummets in areas treated with the Wolbachia-infected mosquitoes. Controlled trials are under way in Asia.

The expansion in Brazil and Colombia will cover far larger population centers, and should provide solid data on Wolbachia’s impact on Zika as well as dengue, Kern said.

Modeling suggests that Wolbachia can persist in mosquito populations for decades, Kern added. That means it might be possible to treat each area once, then see disease reduction for years without any additional cost, unlike regular spraying. “In essence, it’s like we’re vaccinating the land,” Kern said.

Rutgers University senior research scientist Karl Malamud-Roam, who is not involved in the project, praised the Gates Foundation for sponsoring the research — but advised caution.

Just as insects evolve resistance to pesticides, mosquito-borne viruses will eventually fight back against Wolbachia’s choke hold, he said.

“I think it would be misleading to think this would permanently solve the dengue or Zika problem,” he said. “At best it would buy us time.”

Independent scientists who evaluated possible environmental risks found no cause for concern. But Malamud-Roam said a project that seeks to permanently alter mosquitoes requires extra scrutiny.

“There’s no opportunity to say: ‘Whoops, I didn’t mean it,’ if something goes wrong.”