Ehrlichia chaffeensis is a type of bacteria that causes a disease known as human monocytic ehrlichiosis (HME). It is primarily transmitted to humans through the bite of infected ticks, particularly the Lone Star tick. This bacterium infects white blood cells, leading to symptoms such as fever, headache, and muscle aches. Diagnosis of HME is typically made through blood tests that detect the presence of the bacteria or antibodies. Treatment usually involves antibiotics, such as doxycycline, which are effective in clearing the infection. Early detection and treatment are crucial to prevent complications.