Viruses are common etiologic agents of acute polyarthritis worldwide. Rheumatic symptoms are often accompanied by other viral symptoms such as fever, rash, myalgia or nausea, but isolated arthritis may occur resembling or imitating early rheumatoid arthritis. In Europe and North America, the most common arthritogenic viruses include parvovirus B19, rubella, hepatitis B and C, whereas mosquito-borne alpha-viruses are endemic in Africa, Australia, the western Pacific and South America. The latter have attracted the interest of European rheumatologists due to the increasing number of tourists travelling to these regions. Viruses may cause arthritis via various mechanisms, including direct synovial infection leading to cell lysis, immune complex formation or pro-inflammatory cytokine induction. Indirect viral pathogenic effects may induce autoimmune reactions via bystander activation or epitope spreading.