In a stunning twist of microbial survival, scientists have uncovered how a deadly cholera strain used sophisticated viral defense systems to fuel one of Latin America’s worst epidemics—and what it means for the future of infection control.
Key Points at a Glance
- EPFL researchers discovered multiple anti-viral defense systems in epidemic cholera strains
- The WASA lineage resisted dominant phages like ICP1 during the 1990s Latin America outbreak
- Defense systems include abortive infection and countermeasures to phage DNA camouflage
- Findings reveal why this strain spread so aggressively and endured longer than others
- Insights are critical for phage therapy development and outbreak preparedness
Cholera may be an ancient disease, but its bacteria are fighting a very modern war—one being waged at the molecular level against relentless viral predators. New research from EPFL’s Global Health Institute reveals that the strains behind one of the most devastating cholera epidemics in Latin American history harbored a secret weapon: an advanced immune system capable of outmaneuvering the very viruses meant to suppress them.
The story begins in the early 1990s, when a cholera epidemic swept through Peru and much of Latin America, infecting over a million people. While the strain responsible—part of the West African South American (WASA) lineage—was known to belong to the broader “7PET” family that dominates the current global pandemic, it stood apart in one dramatic way: it resisted attacks from bacteriophages like ICP1, viruses known to limit cholera outbreaks in other parts of the world.
Led by Melanie Blokesch and her team at EPFL, the study published in Nature Microbiology dissects how these WASA strains survived the viral onslaught. The answer lies in their genetic code. By examining archived strains from Peru, the researchers uncovered two powerful genomic regions loaded with phage-defense tools: one embedded in the WASA-1 prophage and another within the Vibrio Seventh Pandemic Island II (VSP-II). These functioned like microscopic military bases, deploying an array of strategies to fend off viral invaders.
Among the most fascinating of these tools is the WonAB system, which executes a bold strategy known as abortive infection. Rather than trying to eliminate the virus outright, WonAB sacrifices infected bacterial cells to prevent viral replication—essentially dying for the greater good of the colony. This preemptive containment buys time and space, limiting viral spread.
Other systems, like GrwAB and VcSduA, bring additional layers of protection. GrwAB specifically targets phages that mask their DNA with chemical modifications, while VcSduA covers gaps in defense by countering unrelated virus families. Combined, these systems form a multifaceted shield, allowing WASA strains to persist and proliferate even as phages swirl through water systems trying to take them down.
This arms race between cholera bacteria and phages is more than just a scientific curiosity. It reveals why some outbreaks spiral out of control while others fade. In countries like Bangladesh, the ICP1 phage has long been known to keep cholera in check. But in Latin America, WASA’s phage resistance helped the epidemic rage on unchallenged.
These insights also cast new light on phage therapy, an emerging alternative to antibiotics in the fight against bacterial infections. As multidrug resistance continues to threaten global health, viruses that infect bacteria are being reconsidered as precise, natural treatments. But if pathogens like V. cholerae can evolve to resist these viruses, the promise of phage therapy comes with caveats.
Understanding this dynamic is critical. As lead author David Adams points out, bacterial strains may gain pandemic potential not just through virulence or transmission efficiency, but by acquiring the right viral defenses at the right time. These hidden factors could shape the next outbreak as much as environmental conditions or public health response.
The findings from EPFL offer more than a historical explanation—they provide a genetic map of resilience, one that could help forecast future cholera threats or guide the design of smarter, more adaptive phage-based treatments. In the world of microbial conflict, knowledge is not just power—it’s survival.
