Pathology of alphavirus infections
The incubation period for most alphaviruses is approximately 3 to 15 days. Alphaviruses share a number of clinical features, of which fever, arthralgia, arthritis, and rash are characteristic. Arthritis is typically symmetric and polyarticular and frequently affects the hands, wrists, elbows, knees, and ankles. In the majority of alphavirus infections, joint symptoms resolve after 7 to 10 days, but may persist for >1 year. Researchers speculate that the inflammation associated with an alphavirus infection is due to macrophages releasing proinflammatory cytokines and matrix metalloproteinases.