What is Malaria
Malaria is a potentially fatal mosquito-borne disease caused by protozoan parasites of the genus Plasmodium that are transmitted to humans through the bite of infected female Anopheles mosquitoes. 1
Causative Organisms
Malaria in humans is caused by four distinct protozoan species: 1
- Plasmodium falciparum - the most dangerous species, responsible for most severe cases and deaths 2, 3
- Plasmodium vivax - capable of causing relapsing infections weeks to months after initial infection 1, 2
- Plasmodium ovale - less common, also capable of relapsing 1, 2
- Plasmodium malariae - typically causes milder disease 1
A fifth species, P. knowlesi, has also been recognized as causing human malaria, particularly in Southeast Asia. 1, 3
Transmission
All malaria species are transmitted exclusively by the bite of an infected female Anopheles mosquito. 1 Occasionally, non-mosquito transmission can occur through blood transfusion or congenitally from mother to fetus. 1
Clinical Presentation
The disease characteristically presents with: 1
- Fever - the hallmark symptom
- "Flu-like" symptoms including chills, headache, myalgia (muscle pain), and malaise
- Gastrointestinal symptoms such as nausea, vomiting, and diarrhea 4
- Cough 4
Additional clinical findings may include: 4
- Splenomegaly (enlarged spleen) - a predictive sign with likelihood ratio of 6.6
- Visible jaundice
- Thrombocytopenia (low platelet count <150,000/mL) - occurs in 70-79% of patients and represents the most frequent laboratory abnormality
Severe (Complicated) Malaria
Untreated P. falciparum malaria can rapidly progress to life-threatening complications including coma, kidney failure, pulmonary edema, and death. 4 Severe malaria is defined by the presence of vital organ involvement including shock, pulmonary edema, significant bleeding, seizures, impaired consciousness, and laboratory abnormalities such as kidney impairment, acidosis, severe anemia, or high parasitemia. 2
Global Impact
Malaria remains a major global public health problem with an estimated 300-500 million cases and approximately 1 million deaths occurring annually worldwide. 1 The disease threatens nearly half of the world's population and predominantly affects children in Africa. 3 The mortality rate is approximately 0.26% worldwide and 0.3% in the United States. 2
Geographic Distribution
Malaria transmission occurs in large areas of: 1
- Central and South America
- Sub-Saharan Africa (where most imported cases to the US originate - 80% of cases) 1
- The Indian Subcontinent
- Southeast Asia
- The Middle East
- Oceania
Key Clinical Pitfall
Although malaria can be a fatal disease, severe illness and death are largely preventable when prompt diagnosis is made and proper treatment is administered. 1 Any febrile patient who has traveled to an endemic area should undergo immediate screening, as delayed diagnosis of P. falciparum malaria is associated with increased mortality. 4