Because Robert had spent much of his time outdoors in an area of the world where the Anopheles mosquitoes that transmit malaria are common, the doctors immediately suspected he had contracted malaria. His symptoms matched those generally expected of people with malaria, but to confirm the diagnosis doctors collected a blood sample from Robert to analyze for the presence of the Plasmodium falciparum parasites that cause the disease.
Research malaria on the Centers for Disease Control (CDC) website.
What does a blood smear with malaria look like versus one without?