Reinfection, or ‘superinfection’ as it is sometimes known, means someone contracting a new or secondary infection from a virus with which they have already been infected.

In some viral diseases such as measles or mumps, reinfection does not occur because the original infection creates immunity. In other viral infections such as colds and flu, reinfection occurs frequently, due to different strains of the virus.

While rare, we now know that reinfection with HIV happens through unsafe sex or injecting with other people with HIV. One study has shown it is most likely to occur within the first three years of HIV infection in people who have not previously taken HIV treatments or who have taken treatment breaks.

However, recently there was a documented case where reinfection occurred between two HIV-positive gay men who had been in a long term relationship practicing unprotected sex (i.e. no condoms) and had a history of being non-adherent to their HIV treatments regime.