Activists often criticize “awareness” campaigns for attracting attention without actually alleviating the problem. But in the midst of the global Zika epidemic, two ad agencies in Brazil have turned their ad space into macabre mosquito-killing installations.

Rather than create a TV spot about an issue that’s been in headlines around the world, Rio-based marketing agency NBS enlisted out-of-home agency Posterscope Brasil — both part of Dentsu Aegis Network — to construct a billboard that would attract, trap, and kill aedes aegypti, the mosquito species that carries Zika, as well as other serious viruses like dengue and Chikungunya.

“Zika is a real problem here in Brazil,” said Andre Lima, creative vice president at NBS. “This idea reflects a lot of our beliefs in terms of what communication means in the contemporary world — that speech is not enough anymore. We need to do real things, not just talk about it.”

See also: Drugmakers respond to call for Zika vaccine

The billboards themselves operate on simple principles: fool mosquitoes into thinking they’ve found a human, and then trap them until they die of dehydration. The installations release an airborne combination of lactic acid and carbon dioxide, which mimics the composition of human sweat — a concoction that mosquitoes can detect from as far as 2.5 miles away. Fluorescent lights make the traps even more enticing.

Fans built into the device create positive pressure, which traps mosquitoes that enter the billboard seeking blood. Without a source of food or water, they eventually die and fall to the bottom of the display, where their bodies lie as proof of effectiveness. Cleaners remove about 100 dead insects from each billboard every day.

The slaughter is targeted. “We had to develop a solution that could guarantee that only aedes aegypti mosquitoes would be attracted — not other insects, only this specific one,” said Otto Frossard, planning director at Posterscope Brasil. That way, pollinating insects and beneficial wildlife remained unharmed.

The agencies have initially created two billboards, which were placed 10 days ago in two neighborhoods in Rio de Janeiro hardest hit by Zika — Tijuca and Downtown. The billboards will stay up for about a month before the agencies put up another in western Rio. But they’re hoping they won’t be the only ones.

“We’re now trying to convince brands, people, even governments to come with us to spread this idea,” Lima said.

“That’s why all the technology is open,” Frossard added. The schematics for the billboards are available for free to anyone under a Creative Commons license. The unregulated distribution is “one of the most important ideas in this project,” he said. “If anyone wants to create these billboards, we’re totally open to help.”

While there’s obviously a built-in space in the device for commercial messaging, the design doesn’t require it. NBS and Posterscope have essentially released blueprints for an all-purpose mosquito trap.

Those looking to make their own versions of the billboards should be able to construct one for about 10,000 Brazilian real, around $2,800, though mass production could bring down the cost considerably.

“The greatest thing would be not needing a billboard like this,” Lima said. “But while the situation is out of control, we can all do our part in the effort to stop the disease.”

This story originally appeared in Campaign.