You're lying in a hospital bed, recovering from surgery. Everything went well—until it didn't. A bacterial infection takes hold, and the doctors cycle through antibiotic after antibiotic. Nothing works. The bacteria are resistant to everything in the medical arsenal. This nightmare scenario is becoming increasingly common, but an old solution is making a dramatic comeback: viruses that eat bacteria.
The Enemy of My Enemy
Bacteriophages—or phages for short—are viruses that exclusively infect and kill bacteria. They're the most abundant biological entities on Earth, with an estimated 10³¹ to 10³² phages floating around in oceans, soil, and even inside your body. Every day, they kill 20-40% of all bacteria in the ocean's surface waters. They've been doing this job for billions of years, long before humans arrived on the scene.
French-Canadian microbiologist Felix d'Herelle discovered phages in 1917 and immediately recognized their therapeutic potential. By 1919, he was using them to treat patients with bacterial dysentery. Throughout the 1940s, several American pharmaceutical companies produced phage preparations to fight various infections. The results were promising.
Then penicillin arrived, and everything changed. Antibiotics were easier to manufacture, more stable, and worked against multiple bacterial species at once. Phage therapy was largely abandoned in the West. But in Eastern Europe—particularly Georgia, Poland, and Russia—doctors kept using phages. They never stopped.
When Antibiotics Stop Working
We're now paying the price for our dependence on antibiotics. The CDC estimates that antibiotic-resistant infections cause 2 million illnesses and at least 23,000 deaths annually in the United States alone. Globally, the numbers are staggering: 1.27 million deaths in 2019 directly attributable to resistant bacteria. Projections suggest 39 million deaths over the next 25 years.
The economic toll matches the human cost. Resistant infections drain $55 billion from the U.S. economy each year. Methicillin-resistant Staphylococcus aureus (MRSA) alone kills more Americans than HIV/AIDS and tuberculosis combined.
Meanwhile, the antibiotic pipeline is running dry. Between 1983 and 1987, the FDA approved 16 new antibiotics. Between 2010 and 2016, only six made it through. Developing new antibiotics is expensive, time-consuming, and increasingly unprofitable for pharmaceutical companies. Bacteria evolve resistance faster than we can develop new drugs.
How Phages Work
Unlike antibiotics, which carpet-bomb your microbiome and kill friendly bacteria along with the bad guys, phages are precision weapons. Each phage has evolved to target specific bacterial strains or species. A phage that kills E. coli won't touch the beneficial bacteria in your gut.
When a phage finds its target bacterium, it attaches to the cell surface and injects its genetic material inside. The phage hijacks the bacterial machinery to make copies of itself—anywhere from a few to over 1,000 new viral particles. The bacterium bursts open, releasing the new phages to find more targets. This process, called the lytic cycle, continues until the bacterial infection is eliminated.
This specificity is both phage therapy's greatest strength and its biggest challenge. You can't just grab any phage off the shelf. You need the right phage for the specific bacterial strain causing the infection. Finding that match takes time—sometimes 28 days, sometimes over a year.
A Desperate Gamble That Worked
In 2015, Dr. Tom Patterson lay in a medically induced coma at a hospital in Frankfurt, Germany. The UC San Diego professor had contracted a multidrug-resistant Acinetobacter baumannii infection while vacationing in Egypt. The bacteria had formed biofilms on his organs. No antibiotic could touch it. His doctors gave him hours to live.
His wife, epidemiologist Dr. Steffanie Strathdee, refused to accept that prognosis. She'd heard about phage therapy during her career studying infectious diseases. Working frantically, she contacted researchers worldwide, looking for phages that could kill her husband's specific bacterial strain.
They found them. The FDA granted emergency authorization for the experimental treatment. Doctors administered the phages intravenously and directly into Patterson's abdomen. Within 48 hours, he began to improve. Within weeks, he was awake and recovering. Within months, he walked out of the hospital.
Patterson's case put phage therapy back in the spotlight. He and Strathdee co-founded the Center for Innovative Phage Applications and Therapeutics (IPATH) at UC San Diego—the first dedicated phage therapy center in North America.
The Path Forward
Today, approximately 90 clinical trials involving phages are underway worldwide. The FDA has granted emergency authorization for numerous cases, though phages aren't yet licensed for routine use in the United States. They're classified as biological products, not drugs, which creates unique regulatory challenges.
Phage therapy shows particular promise against ESKAPE pathogens—a group of bacteria that cause difficult-to-treat hospital infections and escape the effects of antibacterial drugs. These include Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species.
Phages can do things antibiotics can't. They can penetrate and degrade bacterial biofilms, those slimy protective layers that make infections so hard to treat. They demonstrate low toxicity to human cells. And perhaps most importantly, they can evolve alongside their bacterial targets. As bacteria develop resistance mechanisms, phages can adapt in response.
The Challenges Ahead
Despite the promise, significant hurdles remain. Manufacturing phages at pharmaceutical scale is complex. Unlike chemically synthesized antibiotics, phages are living biological entities. They're sensitive to temperature and pH. They require careful handling and storage.
Early commercial phage preparations actually included preservatives like phenol, which killed the phages and rendered them useless. This contributed to inconsistent results and damaged phage therapy's reputation.
The specificity that makes phages so effective also complicates their use. Doctors need to quickly identify the exact bacterial strain causing an infection, then find or create a matching phage. This takes time—time that critically ill patients may not have.
There's also the business model problem. Phages are naturally occurring and can't be patented in the same way as synthetic drugs. This makes them less attractive to pharmaceutical companies seeking return on investment.
A Complementary Tool
Phage therapy isn't meant to replace antibiotics entirely. Instead, it offers a complementary approach. For infections that don't respond to conventional treatment, phages provide an option where none existed before. Some researchers are exploring combination therapies, using phages and antibiotics together to attack bacteria from multiple angles.
The medical community is gradually recognizing that we can't antibiotic our way out of the resistance crisis. We need new tools, and phages represent one of the most promising options. They've been fighting bacteria for billions of years. Perhaps it's time we fully enlisted them as allies.
The irony isn't lost on scientists: the solution to our modern medical crisis has been hiding in plain sight all along, waiting in every drop of pond water and handful of soil. We just needed to look back to move forward.