What it is: Chikungunya, a mosquito-borne virus that most often occurs in the Caribbean, Africa, India, and South and Central America, has recently become more common in the United States. Patients usually experience severe joint pain that can last as long as 12 to 15 months. For some, that pain continues for years; those are the cases most likely to be confused with RA.
How it’s different from RA: Infection usually causes a sudden high fever, rash, headaches, and muscle pain, along with joint pain and swelling, according to the World Health Organization. Always let your doctor know if you've traveled to any of the affected regions.