Babesia infection often is asymptomatic or associated with mild, nonspecific symptoms. The infection also can be severe and life threatening, particularly in people who are asplenic, immunocompromised, or elderly. In general, babesiosis, like malaria, is characterized by the presence of fever and hemolytic anemia. Infected people may have a prodromal illness, with gradual onset of symptoms, such as malaise, anorexia, and fatigue, followed by development of fever and other influenza-like symptoms (eg, chills, sweats, myalgia, arthralgia, headache, anorexia, nausea, vomiting). Less common findings include hyperesthesia, sore throat, abdominal pain, conjunctival injection, photophobia, weight loss, and nonproductive cough. Clinical signs generally are minimal, often consisting only of fever and tachycardia, although mild hepatosplenomegaly may be noted. Thrombocytopenia and a normal or low white blood cell count are common. If untreated, illness can last for several weeks or months; even asymptomatic people can have persistent low-level parasitemia, sometimes for longer than 1 year.