The patient develops an acute illness with fever, shivering rigors and flu-like symptoms 1 to 2 weeks after being bitten by an infected mosquito. Headache, nausea and body pains are common in uncomplicated (mild) malaria. The symptoms and signs of malaria are very non-specific, making the clinical diagnosis difficult to confirm or exclude.
Severe headache, repeated vomiting and drowsiness suggest the development of severe malaria. Mild malaria may become severe and even fatal within hours.
Infection of other organs such as the liver (jaundice), gut (diarrhoea), lungs (respiratory distress) and kidneys (oliguria with renal failure) may occur. Massive haemolysis (blackwater fever) causes anaemia, with dark urine.
Anyone who develops fever in a malaria area, or within 2 weeks of leaving a malaria area, must be suspected of having malaria. Thinking of malaria is the most important step in the clinical diagnosis. As the clinical symptoms and signs of malaria are very varied, it is always important to confirm the clinical suspicion. There are often no clinical signs at presentation.
Suspect malaria in anyone with a flu-like illness who lives in or has recently visited a malaria region.