To have a ‘co-infection’ or be ‘co-infected’ means to have infection with two or more viruses at the same time. This term is often used in the context of hepatitis C and HIV, but can also be applied to other combinations of conditions.

There can be implications for care and treatment if someone has a co-infection. For example, one condition might affect how the other progresses, or there may be interactions between the drugs used to treat the two conditions.