Malaria Symptoms and Signs

Malaria is an infectious disease caused by several species of parasites in the genus Plasmodium (P. malariae, P. vivax, P. falciparum, and others). Mosquitoes transmit the parasites to you. About 2 million deaths per year occur due to malaria, the majority of them being children. The largest numbers of deaths and infections occur in sub-Saharan African countries, but malaria can be found in some other tropical areas. Most people diagnosed with malaria in the U.S. have become infected while living in or travelling through a country where malaria is endemic.

After the initial mosquito bite, the incubation period is usually about one to three weeks but may range from a few days to about one year in some individuals. The initial symptoms are flu-like with fever, chills, muscle aches, and headaches. You may develop a cough, nausea, vomiting, and diarrhea. Within a few days, cycles of chills (shaking chills), fever, and sweating episodes that repeat every one, two, or three days (depending on the species) is typical for malaria patients. During these cycles, some patients are profoundly weak and have severe muscle aches and pains. Loss of appetite and weight loss can occur rapidly. You may develop jaundice (yellowing of skin and conjunctiva of eyes). Individuals infected with P. falciparum can further develop bleeding problems, liver and kidney failure, shock, seizures, and coma. P. falciparum infections can be lethal if not diagnosed and treated quickly; even with treatments, about 15%-20% of infected people die.

Diagnosis of malaria by identifying the parasite type(s) in blood smears or by PCR tests helps determine treatment because the tests can identify the infecting species. Treatments are individualized and are based on your clinical situation (child, adult, or pregnant with mild or severe malaria), the infecting species of Plasmodium, and on the drug susceptibility of the infecting species (for example, P. falciparum is resistant to drugs that can treat some other species). Although patients infected with species other than P. falciparum or P. knowlesi may show improvements in the cycles of chills and fevers in about 96 hours, symptoms of weakness or fatigue may remain either constantly or intermittently for months.