What does coinfection mean?
A coinfection is the simultaneous presence of two or more different infectious agents — such as viruses, bacteria, fungi, or parasites — within a single host at the same time. In medicine and public health, the term describes situations where one pathogen's presence coincides with another's, often making each illness more severe or harder to treat than either would be alone. Classic examples include people living with HIV who also acquire tuberculosis or viral hepatitis, and patients whose seasonal flu opens the door to a bacterial pneumonia. Clinicians and researchers use the word constantly in studies of disease interaction, diagnostic strategy, and treatment planning, because a coinfection can change which drugs are safe, which tests to order, and how likely recovery becomes. The word is clinical and neutral in tone, appearing mostly in formal scientific writing rather than casual speech. Understanding coinfection matters because it captures a central truth of infectious disease: pathogens rarely operate alone, and their combined effects can be far greater than the sum of separate infections.
nounThe simultaneous infection of a host by two or more pathogens, such as viruses, bacteria, or parasites.
- Simultaneous infection of one host by two or more distinct pathogens.
- By extension in medical literature: any co-occurrence of multiple infectious agents complicating diagnosis or treatment of a single patient.
"Patients with HIV are at heightened risk of coinfection with hepatitis B or tuberculosis."
"The study examined how influenza and pneumococcal coinfection worsens outcomes in hospitalized children."
"Screening for hepatitis C coinfection is now standard practice when patients test positive for HIV."
Standard plural form; used freely in clinical and research writing when referring to multiple cases or instances.
"Respiratory viral coinfections were documented throughout the winter season."
One patient can be fighting several invaders at once — doctors call it coinfection, and it can make each illness dramatically harder to treat.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of coinfection
Coinfection combines the Latin-derived prefix 'co-' (from 'com-', meaning 'together' or 'with') with 'infection,' from Latin 'inficere,' meaning 'to stain, taint, or corrupt.' The word arose as modern medical science developed germ theory and physicians recognized that multiple pathogens could occupy a single host simultaneously. Its sibling terms — reinfection, superinfection, and cross-infection — share the same Latin root and emerged alongside it as clinicians distinguished between these different patterns of disease.
Related word forms
How coinfection is actually used
Coinfection is a technical term used primarily in medicine, epidemiology, and public health. It appears in formal scientific writing far more often than in everyday conversation. The spelling 'co-infection' with a hyphen is also widely accepted; 'coinfection' without a hyphen has become increasingly standard in American medical literature. It carries a neutral, clinical connotation rather than an emotional one.
Easily confused with coinfection
A superinfection is a second infection that follows an initial one (often resistant or arising on top of treatment), whereas a coinfection is strictly simultaneous.
Reinfection is being infected again by the same pathogen after recovery, while coinfection means harboring two or more different pathogens at the same time.