The enemy of my enemy is my friend. That ancient wartime dictum has taken on new meaning in the struggle against infectious disease, as researchers pit one microbial enemy of human beings against another.

Until recently, the strategy has largely trained on using viruses to kill dangerous bacteria. These bacteriophages—or simply, “phages,” as the viruses are known—might be one solution to the increasing problem of antibiotic resistance in a number of worrisome bacterial strains. The phages hijack a specific type of bacteria, injecting their own viral DNA into the microbes. The code instructs a bacterium to make endless copies of the virus until the germ explodes, which spreads the virus to the next target, and so on. (No one said biology wasn’t brutal.)

The approach, believe it or not, is an old one: In the 1940s, before the widespread use of antibiotics, Eli Lilly sold phages that were targeted against germs ranging from staphylococci to streptococci to E. coli. For those inclined, here’s a fascinating mini-review on phage history.

(And in a side note that speaks to the wonder and importance of basic science: It was by studying bacteria’s defense against these ravaging phages that scientists discovered the gene-editing technique, CRISPR Cas-9. For a discussion of that, see our Oct. 26 Brainstorm Health Daily.)

But now, in the fight against Zika, the battle lines are being redrawn—with bacteria going on the attack against the mosquito-carried virus. Scientists are studying how to use a group of bacteria called Wolbachia, which normally prey on insects (and are considered harmless to humans) to infect mosquitoes that carry Zika—homing in on the bugs’ reproductive systems and making them infertile.

The strategy is not without precedent. A research team in Australia has used Wolbachia to limit the ability of certain mosquitoes to carry dengue fever, which sickens more than 50 million people a year. You can find great articles on the effort here and here. Meanwhile, another laboratory group at the University of Kentucky has licensed its Wolbachia-based biotechnology—which targets the reproductive ability of male Asian Tiger mosquitoes—to a company that is awaiting regulatory approval for its product. (The company already has an experimental use permit for a limited trial in California.)

So who gives the nod to these new anti-infective weapons? Not the FDA, mind you, but rather the EPA: the Environmental Protection Agency. Yes, it’s a brave new healthcare world.

More news below.