Supermodel Bella Hadid shared an Instagram post revealing that she is "finally healthy" after over a decade of battling Lyme disease. A tick-borne illness, Lyme disease is caused by the bacterium Borrelia burgdorferi. The symptoms of the disease include fever, headache, fatigue, and a skin rash called erythema migrans. The 26-year-old was diagnosed with Lyme in 2012.