The Ganges River, which today has a reputation for rampant pollution contrasted with a religious conception of the river as purifying, seems a strange place to look for a method of fighting disease. The river’s purifying properties turn out to have a basis in science—a basis that could also provide a powerful alternative for antibiotics, especially in light of growing concerns about antibiotic-resistant bacteria.
The Ganges stands out from other rivers in many ways, some of which remain scientifically perplexing. For one, despite the millions of people who bathe in the river for religious ceremonies, epidemics occur far less frequently and are less severe than might reasonably be expected. Theories vary about what about the Ganges disinfects the water, but its oxygen levels are remarkably high—in fact, 25 times higher than any other river—as a result. Normally, organic material exhausts the oxygen, but it appears that something in the Ganges kills enough organic material, including bacteria, to counteract this effect despite the massive amounts of bacteria entering the river from human bathing, raw sewage, and corpses.
One theory is that the Ganges may pick up something from the riverbed that explains its self-cleaning properties. More compelling is the view that what cleanses the Ganges is a type of bacteria-killing virus called a bacteriophage. Bacteriophages are parasites that target highly specific types of bacteria—while there are many types of phages, each phage is only capable of killing one or a few related types of bacteria. When killing a host, phages multiply, and the new phages seek out new hosts, exponentially increasing the number of phages and decreasing the number of bacteria.
Bacteriophages are far from unique to the Ganges; they can be found anywhere in the world. How is it that something so widespread might be an explanation for the Ganges’ apparent special properties? While the phages may be what’s killing the bacteria in the Ganges, it seems that their especially potent cleaning effect may well be a result of the polluted water of the river. Since phages are most capable of killing bacteria when they are able to multiply, they threaten large influxes of bacteria in a single location far more than many bacteria spread all over a river. When millions of people simultaneously bathe in the Ganges, the dramatic increase in bacteria creates an environment allowing the phages to take advantage of their exponential growth, rapidly killing huge populations of bacteria.
The bacteriophages’ role in cleaning the Ganges is intriguing for medicine because bacteriophages can be used for phage therapy, an alternative to antibiotics. Indeed, prior to the development of penicillin and other mass-produced antibiotics, doctors used phage therapy to treat many bacterial diseases. Because of the benefits of antibiotics, though, phage therapy fell by the wayside; only Eastern European countries and the former USSR continued research on it.
Now, though, phage therapy is on its way to becoming popular again. Concerns about antibiotic-resistant bacteria such as MRSA are prompting a search for alternative treatments. Since phages work so quickly, they leave less time for bacteria to develop a resistance. One of the most promising advantages—but also the biggest disadvantage—of phages is the specificity with which they target bacteria. Phages’ specificity prevents them from killing the good bacteria in our bodies, eliminating many of the side effects of antibiotics. However, because each type of phage kills only a specific type of bacteria, the use of phage therapy to fight an infection requires quick and accurate identification of the bacteria causing it. This means phage therapy must be developed alongside improvements in tests to identify bacteria and will often involve a phage cocktail consisting of a variety of types of phages to target a wider range of bacteria. Phages can also be engineered to improve their efficacy, deliver vaccines, or produce other benefits.
More testing and research is needed to take full advantage of bacteriophages in medicine, and they will not likely be able to entirely replace antibiotics in the foreseeable future. Nevertheless, they have the potential to drastically improve our ability to combat infections—a potential on display in the Ganges’ mysterious self-purifying ability.