Isolation of rubella virus from synovial fluid in five cases of seronegative arthritis.

A cytopathic agent indistinguishable from rubella virus was isolated from the synovial fluid of five patients (two male and three female). In two patients isolations were made on two separate occasions, and in two others on five separate occasions. The patients ranged in age from 9-58 years, and they presented with a variety of clinical syndromes. In particular, none had clinical features suggestive of recent rubella infection; but most cases had very high serum rubella haemagglutination inhibition titres. The identity of the cytopathic agent was shown by a variety of virological techniques to be rubella virus.