Common early symptoms are gradual onset of fever, malaise, headache, and abdominal pain. Other symptoms are conjunctivitis, facial swelling, sore throat, non-productive cough, retrosternal pain, nausea, vomiting, diarrhea, back pain, and myalgia. Respiratory rate, temperature, pulse rate are increased and blood pressure decreased. Neurological symptoms may also occur, including hearing loss, tremors, and encephalitis. Severe infections produce hemorrhagic manifestations, pleural effusions, and shock.
Pregnant women are more likely to die than are others.
Laboratory animals may be intracerebrally inoculated with acute phase blood or throat washings. Mild cases are similar to a variety of self-limited febrile illnesses. Other possibilities are typhoid fever, typhus, leptospirosis, rickettsial spotted fever, and meningococcemia. Whole blood and platelet transfusions may be given. Centers for Disease Control.