🔬 Coinfection

The infection of a single cell by more than one virus.

by Stephen T. Abedon Ph.D. Steve Abedon, Ph.D., has taught well over 100 individual classes and ~10 individual courses (including introductory biology, microbiology, physiology, biochemistry, etc.) over his 30+ years as a college professor. He has over 150 publications, including multiple monographs, and is ranked in the top 1 or 2 percent among researchers of all disciplines worldwide. His research focuses on bacteriophage biology and phage therapy. (abedon.1@osu.edu)

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About this entry: Coinfection is one of a growing set of phage biology and phage therapy terms defined here. For more phage terms, see Abedon, S.T. (2025). Phage Therapy Annotated Glossary. Preprints.org. 10.20944/preprints202508.0347.v1
To share a particular section, use the 🔗 link beside its heading, which copies a web address that opens the page right there. To cite this page: Abedon, S.T. (2026). Phage Terms. terms.phage.org.  ·  DOI: 10.5281/zenodo.20173633

phage.org/terms/coinfection.html  ·  Abedon’s Books  ·  DOI: 10.5281/zenodo.20173633

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Coinfection: The infection of a single cell by more than one virus.

Discussion

Typically coinfection is seen, in the laboratory and with phages, as infection of a single bacterium by two or more phages of the same phage type. It is possible, however, for multiple phages to infect a single cell where those phages are not of the same type. In fact, it is fairly typical for phages to infect bacteria that are already infected lysogenically, with coinfection therefore occurring between a newly infecting phage and a preexisting prophage.

See superinfection, a term that is similar but not identical to coinfection. See also secondary phage, secondary adsorption, or secondary infection.

Note that coinfection does not necessarily follow co- or multiple adsorptions of a single bacterium since phages can display superinfection exclusion, which means that later phages are blocked from entering the bacterium's cytoplasm. (I use here the phage genome reaching the adsorbed bacterium's cytoplasm as a working definition of "infected".)

Note also that under most circumstances the burst size of a coinfected bacterium is either the same as that of a singly infected bacterium or declines relative to a singly infected bacterium. The latter can be described as a depressor effect.

Coinfection also can be defined more generally in terms of infection of especially multicellular organisms by more than one type of pathogen.

How to cite this page

Abedon, S.T. (2026). Phage Terms. https://terms.phage.org  ·  10.5281/zenodo.20173633

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