Emory University Hospital will begin stockpiling blood plasma from Ebola survivors, treated with a pathogen inactivation system that's never been used before in the United States, the company that developed the technology announced on Friday. So far, the US has had some amazing success in curing Ebola, possibly thanks to experimental plasma treatments. Drawn from survivors, the stuff comes enriched in antibodies that could help to fight off the disease—but it also has the potential to carry other diseases, like malaria, that are common in west Africa where Ebola is raging. The new system will kill off any extra contaminants that may be lurking in this potentially live-saving serum.

It’s the same one, Cerus Corporation’s Intercept system, that will be used in a Gates Foundation-funded study of Ebola treatments in West Africa. The pathogen-killing molecule at the heart of the system is amotosalen, part of a class of three-ringed molecules called psoralens. They’re the compounds in lime that cause what some doctors call “Mexican beer dermatitis”: Get a squirt of the citrus on your skin when you push it into your Corona, spend a few hours on the beach in the sunlight, and the molecules interact with the UV rays to give you a nasty rash.

Cerus' Intercept system activates a molecule with UV light to destroy genetic material in pathogens. Cerus Corporation

Amotosalen doesn't cause dermatitis, but it works by the same mechanism. When technicians add it to blood plasma, it nestles in the middle of DNA and RNA helices, linking the bases on either side. Then, activated by a burst of UV light, it irreversibly bonds to those bases—so the genetic material can’t replicate any more. Pathogens, inactivated.

Europe has long used blood purification systems—Intercept was first approved eight years ago, and there are other techniques, too. But the FDA has been slow to approve the same technology in the US, mostly, it seems, for lack of demand. Last week the agency approved the technique for restricted use in treating the plasma of Ebola survivors.

We already screen donated blood for several common contaminants: infectious diseases like hepatitis, West Nile, and Chagas disease. (The Red Cross also screens for HIV, but unfortunately the FDA still prohibits gay men from donating blood.) Those screens mean it’s very safe to use donated blood in the United States. But that can change when new diseases enter the pipeline—ones that we don’t test for, or ones that we don’t even know exist.

For the FDA, the tipping point might have been two diseases that are new to the US, Chikungunya and dengue. As temperatures rise, mosquitoes migrate northwards, carrying diseases that have historically been stuck in warmer, tropical countries. So in October, the FDA approved the Intercept system for use in areas like Florida and Texas where the mosquito-borne diseases are becoming a problem. (Nobody's used the treated plasma yet.) Because they’re so uncommon here, we don’t test for those two diseases, or malaria. But soon, testing may not be enough.

“There’s an increasing realization that it’s challenging to be proactive about epidemics with our current testing paradigm,” said William ‘Obi’ Greenman, Cerus’ president and chief executive officer. We may be confronting enough new pathogens in this rapidly changing climate of ours that inactivation will become necessary to keep our blood supply safe. If so, the FDA is ready; Greenman says they’re likely to decide whether to approve the Intercept system to treat all donated plasma in the next several months.

*Editor's note: this story has been amended to reflect that Emory University Hospital and not the FDA will be stockpiling treated plasma from Ebola patients. *