< Volunteers Who Say 'Bite Me' Are Helping To Win The War Vs. Mosquitoes

MICHEL MARTIN, HOST:

What is the deadliest animal on the planet? Would you guess that for centuries it's been the tiny annoying mosquito? Mosquitoes still kill about half a million people each year. The Zika virus is just the latest example of the damage they can inflict, yet there is good news on the mosquito front. And one of the surprising key players fighting them is the U.S. military. NPR's Greg Myre reports.

GREG MYRE, BYLINE: The headquarters for the U.S. military's longest war isn't at the Pentagon. It's the war against mosquitoes here at the Walter Reed Army Institute of Research.

This suburban Washington lab is part of a global effort making mosquitoes far less deadly. But it does require volunteers. And their mission is to place a bare arm on a mug of mosquitoes infected with malaria and sit still while the parasites enjoy a feast.

The volunteers will malaria, and this allows the military to see how humans respond to the illness.

DEBORAH YOURICK: And that's the only way you can actually test a vaccine or an anti-malarial.

MYRE: That's Deborah Yourick, director of science education at Walter Reed.

YOURICK: It's a controlled malaria infection, one we know we can cure.

MYRE: Mosquitoes have chomped on 2,200 people in this malaria challenge. Volunteers are bitten at least five times. Some have been bitten a thousand times over several sessions. They've all survived, which shows how far we've come. The Zika virus is the latest reminder that mosquitoes have been the deadliest animal for centuries, but there's actually very good news on the mosquito front. For the first time in forever, humanity is getting the upper hand. According to the World Health Organization, mosquito-related deaths have fallen from an estimated 1 million a decade ago to a half million today. How did that happen? Well, scientists keep inventing more effective sprays and medicines. But the biggest differences come from bed nets coded with insecticides. They've saved millions of lives, particularly among children in Africa who account for the vast majority of victims. Still, many in this field, like Army Maj. Jeffrey Clark, say it's far too early to celebrate.

JEFFREY CLARK: I would caution in getting too optimistic because I think it was the late 1950s that we thought for sure within four or five years malaria would be wiped from the face of the earth.

MYRE: The first big breakthrough came around 1900 when Gen. Walter Reed linked mosquitoes to the diseases they transmit. A few years later, the military took over the Panama Canal project after yellow fever wiped out workers and bankrupted the French effort. When the Americans drained all the stagnant water...

YOURICK: Yellow fever infections went down dramatically, went to nearly nothing.

MYRE: That's Deborah Yourick again.

YOURICK: It was the first - uh-oh, this is where it's coming from. It's not coming from what are called fomites, which is...

MYRE: Right, bad air...

YOURICK: ...You know, bad air or, you know, vomits or sweat, whatever - it wasn't that. It was the mosquito.

MYRE: Yet every time science advances, mosquitoes adapt. They become resistant to sprays and medicines. They're even outsmarting bed nets by dining at an earlier hour.

CLARK: So instead of biting in the middle of the night now when people are sleeping, they're biting in the evening when they're sitting outside by the fire. So the bed nets are becoming less and less effective.

MYRE: That's Maj. Clark again. The military has been working with pharmaceutical companies on a malaria vaccine for years. That would be a huge advance, but it remains elusive. So the fight is still taking place on several fronts - with sprays and pills and nets. The battle isn't over, but humanity finally seems to be winning. Greg Myre, NPR News, Washington.

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