Scientists are re-exploring "phage therapy," the use of viruses to kill antibiotic-resistant bacteria, according to The Washington Post.

Why it matters: Antibiotic resistant bacteria pose one of the biggest threats to human health, according to the World Health Organization. Bacteriophage therapy could be another option as resistance to existing antibiotics grows because of the large number of phages on Earth (in excess of 10 million trillion trillion), each likely to target a different species of bacteria.

How it works: Bacteriophages kill specific bacteria by entering the cells and causing them to burst. To figure out which bacteria are being targeted, researchers take a sample from a patient, grow them with phages and see which cells they kill. They then grow that phage in large batches, purify it and administer it to the patient. The process takes five to 10 days, however scientists believe they will be able to shorten that time frame. The approach hasn't been approved for general use in people but WaPo says most scientists believe they are safe, in part because we are exposed to them daily, and the therapy has been used in a handful of emergency situations.