Viruses have a bad press, and this is not surprising. COVID-19 is caused by the virus SARS-CoV-2 and the pandemic is estimated to have caused at least 15 million deaths. But our planet Earth hosts enormous numbers of viruses and not even one in a million infects us humans, it is just that these less than one in a million viruses are the ones we mostly care about. So 99.999% + of Earth’s viruses infect other organisms. When they infect us and make us sick that is bad but when they infect an organism we don’t like that could be good.
This has motivated a century of research into using bacteriophages* – viruses that infect bacteria – to kill bacteria that are infecting us. The idea is the same as with antibiotics. Antibiotics are chemicals that are toxic to bacteria and poison the bacteria (but not us). Bacteriophages infect bacteria and when they reproduce rapidly they kill the bacteria. So a virulent bacteriophage will rip through the population of bacteria infecting someone, killing most of the bacteria, and so acting just like an antibiotic. Viruses are very specific, a bacteriophage typically infects only one type of bacteria, they cannot infect our cells.
But despite a century’s work, bacteriophages are not used at any scale in humans. They do not fit well into the tightly-regulated big-business pharmaceutical model. This is well described in The Good Virus: The Untold Story of Phages: The Most Abundant Life Forms on Earth and What They Can Do For Us, by Tom Ireland.
One of things I learnt from Tom Ireland’s book is that bacteriophages are being trialled in agriculture, as an alternative to the widespread use of antibiotics in industrial farming. I assume the regulations here are less strict so it is easier to get approval.
It will be interesting to see if they take off in agriculture, if so this may make it easier to get approval for human use. Bacteria are constantly evolving resistance to antibiotics and people are dying of antibiotic-resistant infections, so we need new ways to attack bacteria. And bacteriophages have been evolving to avoid bacteria evolving resistance to them, for billions of years.
* For historical reason, viruses that infect bacteria are usually called bacteriophages not viruses.
Chance & Necessity 