Prevalence of antibodies against a Sindbis-related (Pogosta) virus, a potential cause of chronic arthritis

Abstract

A disease characterised by arthritis, rash and fever was described in Northern Finland in 1974 and named, according to the region, Pogosta disease. It closely resembles Ockelbo disease in Sweden, and Karelian fever, occurring in Western Russia. When analysing the clinical picture during an outbreak we found that 93% of the patients had joint inflammation, 40% with polyarthritis. Rash was seen in 88% of the patients, and 23% had fever. It has been suggested that the disease is self-limiting, but in a follow-up study we found that 50% of the patients suffered from chronic muscle and joint pain at least 2.5 years after the initial symptoms. There have been several outbreaks of Pogosta disease in Northern Karelia. They seem to occur every seven years. It has been assumed that Pogosta disease is locally restricted, as is described also for Ockelbo disease and Karelian fever. All three diseases are attributed to Sindbis-related arboviruses, and the spreading vector appears to be the late summer mosquitoes. Pogosta disease is considered to affect mostly young adults and middle-aged people. In an epidemiological study we analysed, using a semi-purified Sindbis-virus as antigen, antibodies against Pogosta disease in 2250 serum samples. Four hundred sera were from healthy blood donors and 1850 samples from patients who were suspected to have some viral infection. The samples represented different parts of Finland. Eleven percent were positive for IgG and 0.6% for IgM class antibodies. The antibody prevalence was almost equally distributed throughout the country, highest in Western Finland (17%). Of all samples with IgG class antibodies 25% were taken from children below 10 years. Three conclusions can be made: 1) Pogosta disease is more common than was thought until now. 2) It is not only restricted to Eastern Finland but is spread throughout the whole of Finland. 3) It is also common in children, in contrast to an earlier belief.