A number of virus infections can induce acute, non-erosive arthritis. A thorough exploration of the patient's history and serological testing for viral infections are crucial to the diagnosis of virus-induced arthritis. Musculoskeletal involvement in infection with the HIV-virus is not a rare feature and will have to be considered more often in cases of acute arthritis, as the prevalence of HIV-infection is increasing. Whether chronic arthritis, like rheumatoid arthritis, is induced by viral infection, is still a subject of intensive research efforts.