Phage

Phage (pronounced feyj)

In microbiology & virology, a virus parasitic towards bacteria; a truncation of bacteriophage.

1917: from the Ancient Greek φάγος (phágos) (eater), from φαγ (phag), aorist (the tense of Greek verbs that most closely corresponds to the simple past in English) stem of ἐσθίω (esthíō) & ἔδω (édō) (to eat, to consume) and thus a combining form meaning “a thing that devours,” used in the formation of compound words, especially the names of phagocytes.  The noun bacteriophage (virus that parasitizes a bacterium by infecting it and reproducing inside it) was adopted in English in 1921, from the 1917 French original bactériophage, the construct being bacterio- (a combining form of bacteria) + -phage.

Some viruses can be helpful: A depiction of phages phaging.

Not all viruses are bad like SARS-CoV-2.  A bacteriophage, known almost always as a phage, is a virus which infects and replicates within bacteria.  Phages are composites of proteins that surround a DNA or RNA genome and may encode any number of genes from a handful to many hundreds.  Phages replicate within the bacterium following the injection of their genome into the target cytoplasm.  Phages exist naturally in the environment and are among the most common and diverse entities on earth.  Serious research began in several parts of Europe during the late nineteenth century and have been used for almost a century as anti-bacterial agents the former USSR and Central Europe.  In the West, phage therapy (using specific viruses to fight difficult bacterial infections) has been of interest for some time, attention heightened as the problem of antibiotic-resistant bacteria (superbugs in the popular imagination) began to grow in severity (the US CDC (Centers for Disease Control and Prevention) attributes one death every 15 minutes in the US to superbugs).  Since the discovery of penicillin, antibiotics have been used as a reliable cure for those suffering from once lethal bacterial infections but, over decades, a handful (compared with the trillions and trillions killed) of bacteria have proved resistant to antibiotics and as these survivors multiply, new infections emerge.  Historically this had prompted the development of revised or new antibiotics but the biological arms race has reached the point where some infections caused by called antibiotic resistant bacteria cannot be treated and for many other serious infections, the number of potent “last resort” antibiotics is dwindling.

Hence the interest in phages, a type of “friendly virus” which can be weaponized to fight even the most virulent and persistent bacterial infections.  Phages work as well as they do because viruses like the tiresome SARS-Cov-2 that makes humans sick, phages can infect only bacteria and are selective about which they target, a vital aspect of their role in medicine because human survival depends on the billions of bacteria in our bodies.  These phages are far from rare, existing in the natural environment almost everywhere on the planet and scientists conducting research find dirty waterways or damp, aerated, warm, decaying soil (both areas where high bacterial growth might be expected) are good places to collect samples.  The advantages phages offer are well known but there are also drawbacks and indeed some of the features of phages manifest as both.  For example, the great specificity of phages helpful in that they can be administered safely with the knowledge that no other organisms will be harmed but this can be a practical disadvantage in clinical medicine when it’s not known exactly which bacteria need to be targeted, which is why broad-spectrum antibiotics proved so effective at scale.  Being wholly natural, the shelf-life of phages is highly variable and there’s little experience in their administration beyond some communities in Eastern Europe where they’ve been part of medical practice for over a century.  Additionally, bacteria can develop resistance even to phages and one practical impediment to deployment not well recognized until recent years is that compared to chemical molecules, phages are quite big and there are sites in the human body which will be inaccessible.

However, looming over the treatment of bacteriological infection is the economics of the pharmaceutical business (big-pharma).  It was the ability in the twentieth century of the industry to mass-produce antibiotics at scale and at astonishingly low cost which meant what little research on phages was being undertaken quickly was abandoned; antibiotics truly were miracle drugs.  However, the economics which made antibiotics attractive to the public health community meant they added comparatively little to the profits of big-pharma compared with something lucrative like a blood-pressure drug which a patient would be required to take every day for the rest of their lives.  A cheap antibiotic, needed disproportionately in low-income countries was a less attractive path for the billions of dollars (and usually years of trials) required to bring a new drug to market.  What the industry likes are drugs which can be mass-produced to treat the “curse of plenty” diseases of first world customers.  Unless there’s some sort of molecular breakthrough (presumably at the level of DNA), phages seem likely for the foreseeable future to remain a niche treatment.

Little killing machines: Matt Cirigliano's graphical depiction of phages in action.

Potential phage research subject: In 2014, while on holiday in French Polynesia, Lindsay Lohan was infected with Chikungunya, a virus (CHIKV) spread by the bites of infected (usually the Aedes) mosquitoes; it causes severe joint pain, headache, fever, nausea, fatigue and rash and flu-like symptoms but can occasionally be fatal.  The word Chikungunya from the Kimakonde language and translates literally as "to become contorted"; the condition was first isolated in Tanzania in 1952 before spreading around the Indian Ocean region, south-east Asia and the Pacific islands, cases emerging for the first time in the Caribbean in 2013 while until recently, it was rare in the US and Europe, most victims having traveled from affected areas.  There is no cure or vaccine, and the illness can last from several days to as long as a few weeks.  Ms Lohan advised those in susceptible regions to use bug spray and posted on Instagram a photo from the beach, captioned "I refuse to let a virus effect (sic) my peaceful vacation."

In August 2025, wire services began reporting Sri Lanka was facing its worst Chikungunya outbreak in two decades, public health experts linking the spread (the virus since earlier in the year widespread in southern China) to climate change, mosquito habitats spreading as weather patterns shift.  In Beijing, despite Chikungunya not being spread by human-to-human contact, the ruling CCP (Chinese Communist Party) ordered mass quarantines with the southern province of Guangdong thought worst afflicted.  With the CCP having perfected the protocols established during the Covid-19 pandemic, infected residents were confined to “quarantine wards” in hospitals and placed in beds covered by mosquito nets; unless testing negative, there they must remain for seven days.  The CCP is applying technology to the problem, swarms of drones being deployed spraying insecticide, the missions said to be both “targeted” (ie the drone’s sensors being used by an on-board AI (artificial intelligence) engine to detect possible mosquito breeding areas) and “carpeting” (ie soaking a defined area in a way analogous to the “carpet bombing” (also as “area bombing”) of cities which was one of the more controversial strategies of World War II (1939-1945).

Chikungunya virus (CHIKV) assembly and egress.

Biological warfare is also being pursued: (1) millions of non-transmissive “elephant mosquitoes” being released, their larvae devouring the smaller, virus-carrying pests and (2) thousands of mosquito-eating fish being placed in public ponds.  Once the Aedes mosquito becomes endemic to an area, it’s reproduction can be difficult to restrict, one Chinese public health specialist confirming breeding was possible in as small a quantity of liquid as that which might accumulate in an upturned bottle cap.  In Guangdong, representatives of the CCP vowed to take “decisive and forceful measures” with residents ordered to remove stagnant water (threats of fines up to US$1,400 a nudge towards compliance).  As well as a north-south thing, climate change is also an east-west phenomenon and disease transmission vectors can travel with weather patterns, the ECDC (European Center for Disease Prevention and Control) in July reporting some quarter-million cases with 90 confirmed deaths.  The US CDC in August issued a Level 2 travel notice (practice enhanced precautions) for those going to China, two notches down for Leve 4 (avoid all travel to the region).