Conditions · Systemic conditions
Malaria !
Malaria is a parasitic infection spread by Anopheles mosquito bites that causes cycles of fever and destroys red blood cells; one type can quickly turn deadly.
Updated 2026-10-30
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In biochemistry
Microorganisms that cause it
In immunology
In the clinical exam
In physiology
Why it happens
- Systemic effects of inflammation: fever, acute-phase proteins, leukocytosis, sepsis
- Health effects of climate change
- Anemia physiology and compensation
- Blood cells on a smear: erythrocytes, leukocytes, platelets
What it is
A parasitic infection by Plasmodium species, spread by the bite of infected female Anopheles mosquitoes, that causes cyclic fever and destroys red blood cells; P. falciparum can quickly become life-threatening.
Who gets it
Endemic in tropical regions. In Colombia transmission is mainly in lowland rural areas such as the Pacific coast and the Amazon; P. vivax and P. falciparum are the main species, and their share varies by area. In 2016 Colombia reported 83,356 cases, 57% due to P. falciparum and 39.7% to P. vivax (preliminary figures from non-WHO sources).
Causes
- Plasmodium falciparum, P. vivax, P. malariae, P. ovale and P. knowlesi
- Bite of an infected female Anopheles mosquito
- Less often: blood transfusion, shared needles or mother-to-child (congenital) transmission
Risk factors
- Living in or travelling to endemic areas, especially rural lowlands
- Outdoor work at dusk and night (mining, farming, logging)
- No prior immunity: young children, travellers, pregnant women
- Not using bed nets, repellents or chemoprophylaxis when indicated
- Pregnancy and HIV infection (more severe disease)
Pathophysiology
Sporozoites infect the liver, then merozoites invade red cells and multiply; synchronous rupture of red cells causes the fever paroxysms and hemolysis. P. falciparum-infected cells stick to small-vessel walls (sequestration), impairing flow to brain, kidney and other organs. P. vivax and P. ovale can stay dormant in the liver (hypnozoites) and relapse.
Classification
- Uncomplicated malaria
- Severe (complicated) malaria
- By species: falciparum, vivax, malariae, ovale, knowlesi
- Malaria in pregnancy and congenital malaria
Symptoms and signs
- Fever with chills and sweats, sometimes in cycles
- Headache, muscle aches and malaise
- Nausea, vomiting or diarrhea
- Pallor and fatigue from anemia
- Enlarged spleen and liver
- Mild jaundice
Diagnosis
- Clinical
- Fever in anyone who lives in or has visited an endemic area is treated as possible malaria until tested; clinicians look for signs of severe disease.
- Tests
- Thick blood smear detects and counts parasites; thin smear identifies the species. Rapid antigen tests help where microscopy is not available. Blood count, glucose, kidney and liver tests, and lactate assess severity.
- Imaging
- Not needed to diagnose; chest X-ray or brain imaging only when complications are suspected.
Differential diagnosis
- Dengue
- Typhoid fever
- Leptospirosis
- Viral hepatitis
- Bacterial sepsis
- Meningitis or encephalitis
Goal of treatment
Clear the parasite quickly, prevent progression to severe disease and death, eliminate dormant liver forms in vivax and ovale malaria, and reduce transmission.
Treatment
- Medical
- Uncomplicated malaria: oral antimalarials chosen by species and local guidelines, such as artemisinin-based combination therapy for falciparum and chloroquine where vivax remains sensitive.
- Medical
- Vivax and ovale: an 8-aminoquinoline (primaquine or tafenoquine) to clear liver hypnozoites, after G6PD testing.
- Acute
- Severe malaria: hospital care with intravenous artesunate, management of glucose, fluids, anemia (transfusion), seizures and kidney failure.
- Follow-up
- Repeat smears to confirm parasite clearance and follow-up for relapse.
Drugs for this condition
Complications
- Cerebral malaria
- Severe anemia
- Acute kidney injury
- Acute respiratory distress syndrome
- Hypoglycemia and metabolic acidosis
- Splenic rupture
- Low birth weight, miscarriage or stillbirth in pregnancy
Prognosis
Uncomplicated malaria treated early usually resolves fully. Severe falciparum malaria carries a substantial risk of death even with treatment; vivax can relapse months later without radical cure.
Prevention
- Insecticide-treated bed nets and indoor residual spraying
- Repellents and protective clothing
- Chemoprophylaxis for travellers, according to the destination
- Early diagnosis and treatment to cut transmission
Test yourself
Think of the answer, then tap the question to see it.
Which Plasmodium species causes most severe malaria and why?
P. falciparum: infected red cells stick to small-vessel walls (sequestration), it reaches high parasite densities and it invades red cells of all ages.
What is the difference between the thick and the thin blood smear?
The thick smear concentrates blood to detect parasites and count them; the thin smear shows parasite morphology to identify the species.
Why do P. vivax and P. ovale relapse and how is this prevented?
They leave dormant liver forms (hypnozoites). An 8-aminoquinoline clears them; G6PD deficiency must be ruled out first because of hemolysis risk.
Which features define severe malaria?
Impaired consciousness or seizures, severe anemia, hypoglycemia, acidosis, kidney injury, pulmonary edema, shock, bleeding, jaundice or high parasitemia (criteria vary slightly).
Related conditions
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Malaria (StatPearls (NCBI Bookshelf), 2023); Malaria in Brazil, Colombia, Peru and Venezuela: current challenges in malaria control and elimination (Malaria journal, 2017) · adapted, CC BY 4.0.
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