Malaria

Malaria is a potentially fatal parasitic disease caused by Plasmodium species, transmitted by the Anopheles mosquito. It is a medical emergency — clinical deterioration or death can occur within 24–36 hours in a non-immune patient. [1-2] Approximately 2,000 cases are diagnosed annually in the US, predominantly in returning travelers. [1]

• Travel history is the single most critical HPI element — destination, dates, duration, rural vs. urban exposure, and time since return [1-2]
• Chemoprophylaxis use: agent, adherence, timing of discontinuation
• Symptom onset relative to return: P. falciparum typically presents within 4 weeks; P. vivax/ovale can present months to >1 year later [1][3]
• Symptom characterization: fever (often paroxysmal), chills/rigors, headache, myalgias, malaise, nausea/vomiting, diarrhea, abdominal pain, cough, fatigue [1][4]
• Classic cyclical fevers (q48h for P. falciparum/vivax/ovale, q72h for P. malariae) are highly variable and should not be relied upon for diagnosis [2-3]
• Important negatives: rash (uncommon), neck stiffness (suggests meningitis), hemorrhage (suggests viral hemorrhagic fever) [2]
• Prior malaria episodes, blood transfusion history, organ transplant history [3]

• Altered mental status / impaired consciousness (GCS <11) — cerebral malaria carries ~40% case fatality [3]
• Seizures (>2 in 24 hours)
• Respiratory distress (SpO₂ <92%, RR >30, labored breathing) — suggests acidosis or pulmonary edema [4]
• Prostration (unable to sit/stand/walk)
• Shock (capillary refill ≥3 sec, SBP <80 mmHg in adults, <70 mmHg in children) [4]
• Hypoglycemia (glucose <40 mg/dL)
• Significant bleeding (hematemesis, melena, mucosal bleeding)
• Jaundice with high parasitemia
• Parasitemia ≥2% in non-immune travelers or ≥5% by any measure defines severe disease [2][4]
• Inability to tolerate oral medications [4]

Uncomplicated malaria (chloroquine-resistant or unknown)

• Artemether-lumefantrine (Coartem) — first-line ACT; administer with fatty food; safe in all trimesters of pregnancy [4-5]
• Atovaquone-proguanil (Malarone) — alternative; contraindicated in pregnancy and infants <5 kg [5]
• Quinine + doxycycline/tetracycline/clindamycin — 7-day regimen [5]

Uncomplicated malaria (chloroquine-sensitive)

• Chloroquine phosphate[5]

Severe malaria

• IV artesunate — 2.4 mg/kg at 0, 12, and 24 hours, then q24h; for patients <20 kg use 3.0 mg/kg [1][4]
• Transition to oral ACT once parasitemia ≤1% and patient tolerates PO (minimum 24h IV) [4]
• If artesunate unavailable: IM artemether or IV quinine [4]

Relapse prevention (P. vivax/P. ovale)

• Primaquinetafenoquinemust check G6PD[5-6]

Medications to avoid

• Do not treat with the same agent used for prophylaxis [2]
• IV quinidine is no longer available in the US [1]

Key caution: Post-artemisinin delayed hemolysis can occur 1–3 weeks after IV artesunate (4.8% of US patients) — monitor hemoglobin, LDH, and haptoglobin for 4 weeks. [1]

The following table from the 2025 NEJM review summarizes treatment regimens:

• Administer artemether-lumefantrine with fatty food or milk to optimize absorption — this is clinically significant and affects drug levels [4]
• Maintain adequate hydration, especially in febrile patients
• Monitor and correct hypoglycemia aggressively (glucose <40 mg/dL defines severe malaria) — quinine and severe malaria itself both cause hypoglycemia [4]

• Neuro: headache, confusion, altered mentation, seizures, visual changes
• GI: nausea, vomiting, diarrhea, abdominal pain (can mimic gastroenteritis)
• Pulmonary: cough, dyspnea, chest tightness (ARDS can develop, often after treatment initiation) [4]
• Heme: pallor, easy bruising, dark urine (blackwater fever)
• MSK: myalgias, arthralgias
• GU: decreased urine output (AKI)
• OB: pregnancy status — pregnant women are at increased risk for hypoglycemia, severe anemia, and placental malaria [3-4]

• Confirm travel itinerary with companions; patients may underreport rural or nighttime mosquito exposure
• Immigration history — patients from endemic regions who have been in the US may have lost partial immunity (typically within ~6 months) [1][3]
• Blood transfusion or organ transplant history (rare non-mosquito transmission)
• Heritable protective factors: sickle cell trait (HbAS) provides 85–90% protection against severe P. falciparum; G6PD deficiency may confer some protection but is critical to identify before primaquine/tafenoquine use [4]
• Duffy-negative blood type (common in sub-Saharan Africans) provides near-total protection against P. vivax [4]

• Travel to sub-Saharan Africa (highest risk; most P. falciparum) or South/Southeast Asia, Central/South America [1]
• Non-immune travelers (no prior malaria exposure)
• Visiting friends and relatives (VFR travelers) — often do not take prophylaxis
• Non-adherence or suboptimal chemoprophylaxis
• Pregnancy (especially primigravidas) [3]
• HIV/immunosuppression — increases parasitemia and severity [4]
• Children <5 years in endemic areas
• Splenectomy or functional asplenia
• Iron-replete status (iron deficiency is paradoxically protective) [4]

• Prior malaria episodes (species, treatment, complications)
• Splenectomy — increased risk of severe parasitemia
• Sickle cell disease/trait — protective but important for management
• G6PD status — must be known before prescribing primaquine or tafenoquine [6]
• HIV status — affects immunity and drug interactions
• Pregnancy — alters treatment selection and risk profile [4]
• Chronic kidney or liver disease — affects drug dosing and severity assessment
• Prior chemoprophylaxis regimen and adherence

• Vitals: Fever (often >39°C, may be absent between paroxysms), tachycardia, hypotension (severe), tachypnea
• General: Diaphoresis, rigors, prostration, pallor, jaundice [8]
• HEENT: Scleral icterus, pallor of conjunctivae
• Lungs: Crackles/crepitations (pulmonary edema, ARDS); deep labored breathing (Kussmaul — acidosis) [4]
• Abdomen: Hepatomegaly, splenomegaly (tender), RUQ tenderness [8]
• Neuro: GCS assessment, meningismus (absent in malaria — if present, consider meningitis), seizure activity, abnormal posturing [4]
• Skin: Petechiae (DIC), no rash expected (rash suggests alternative diagnosis)
• Extremities: Capillary refill (≥3 sec = compensated shock), cool peripheries [4]

• Thick and thin blood smears (Giemsa-stained) — gold standard; species identification and parasitemia quantification [2][5]
  • Repeat q12–24h × 3 if initial smear negative [2]
  • After treatment: repeat q12–24h to confirm declining parasitemia [1]
• Rapid diagnostic test (BinaxNOW) — results in 2–15 minutes; sensitivity 99.7% for P. falciparum at >5,000 parasites/µL; less sensitive for non-falciparum species [1]
  • Must be confirmed by microscopy[9]
• CBC: Anemia, thrombocytopenia (common and helps differentiate from viral illness), leukocytosis or leukopenia [5]
• CMP: Creatinine (AKI if >3 mg/dL), glucose (hypoglycemia <40 mg/dL), bilirubin (>3 mg/dL in severe), transaminases (elevated AST/ALT) [4-5]
• Lactate: ≥5 mmol/L defines severe disease [1]
• Coagulation studies: PT/INR, fibrinogen (DIC screen)
• LDH, haptoglobin, reticulocyte count — hemolysis markers
• Blood gas: Base deficit >8 mEq/L or bicarbonate <15 mmol/L = severe acidosis [4]
• G6PD level — before prescribing primaquine/tafenoquine [6]
• Type and screen — anticipate transfusion needs
• Blood cultures — to rule out concurrent bacteremia

• Chest X-ray: Indicated if respiratory symptoms, SpO₂ <92%, or suspected ARDS/pulmonary edema [4]
• CT head: If altered mental status to rule out other intracranial pathology; cerebral malaria is a clinical diagnosis
• Routine imaging is not required for uncomplicated malaria
• Abdominal ultrasound: May show hepatosplenomegaly; consider if concern for splenic rupture

• PCR (nucleic acid testing): More sensitive than microscopy; useful for species confirmation and detecting mixed infections; results not immediately available — not for initial clinical decision-making [5][9]
• Point-of-care glucose: Check immediately and serially — hypoglycemia is both a complication and a treatment side effect (quinine) [4]
• Point-of-care lactate: Rapid severity assessment
• CDC Malaria Hotline (770-488-7788, after hours 770-488-7100): Available 24/7 for diagnostic and treatment guidance [2][9]
• CDC telediagnosis service: Assists with blood smear interpretation remotely [9]

• Obtain ECG if using quinine (QT prolongation risk), hydroxychloroquine (QT prolongation), or mefloquine (neuropsychiatric effects) [5]
• Monitor for QTc prolongation — particularly with quinine and chloroquine
• Assess for arrhythmias in severe malaria with acidosis, electrolyte derangements, or shock

Severity stratification is the most critical assessment step and determines treatment pathway:

• Uncomplicated malaria: Symptomatic parasitemia without WHO severe criteria; can tolerate oral medications [1]
• Severe malaria (any one criterion): GCS <11, seizures, parasitemia ≥5% (or ≥2% in non-immune), AKI (Cr >3 mg/dL), hypoglycemia (<40 mg/dL), ARDS, shock, severe anemia (Hgb <7 in adults), acidosis (lactate ≥5, bicarb <15), jaundice with high parasitemia, DIC, prostration, inability to take PO [2][4]

The presence of multiple complications dramatically increases mortality — from ~6% with one complication to ~43% with multiple. [4] Impaired consciousness and respiratory distress are the strongest predictors of death. [10]

Initial stabilization (severe malaria)

• ABCs, IV access, continuous monitoring
• IV artesunate 2.4 mg/kg at 0, 12, and 24 hours (minimum 3 doses), then q24h until PO tolerated and parasitemia ≤1% [1][4]
• Aggressive glucose monitoring and correction (D50 bolus PRN)
• IV fluids — use judiciously; avoid fluid overload (ARDS risk) [2]
• Blood transfusion for severe anemia (Hgb <5 g/dL in children, <7 g/dL in adults)
• Antipyretics (acetaminophen)
• Transition to full oral ACT course once criteria met [4]

Uncomplicated malaria

• Artemether-lumefantrine (with fatty food): 4 tablets BID × 3 days (adults) — first two doses 8 hours apart [4-5]
• OR Atovaquone-proguanil: 4 adult tablets daily × 3 days [5]
• OR Chloroquine (if chloroquine-sensitive species) [4]

Radical cure (P. vivax/P. ovale)

• [5-6]

Consult infectious disease and contact the CDC Malaria Hotline for all confirmed cases. [2][9]

Admit (ICU for severe)

• Any WHO severe malaria criteria [2]
• P. falciparum with parasitemia ≥2% in non-immune patients [4]
• Inability to tolerate oral medications
• Pregnant patients [2]
• Immunocompromised patients (HIV, asplenic) [2]
• Children and patients with no prior malarial immunity [2]
• Uncertain species identification with clinical concern

Outpatient treatment may be considered if

• Confirmed uncomplicated malaria with no severe criteria
• Able to tolerate oral medications
• Reliable follow-up ensured
• Non-P. falciparum species with low parasitemia [2]

Most patients will require admission for treatment initiation and monitoring. [8]

• Post-treatment blood smears q12–24h until parasitemia clears (two consecutive negative smears) [1]
• Monitor for post-artemisinin delayed hemolysis for 4 weeks after IV artesunate — check CBC, LDH, haptoglobin at 1, 2, 3, and 4 weeks [1]
• P. vivax/P. ovale: Counsel on relapse risk if radical cure not completed; relapses can occur months later [3]
• Report all cases to the state health department [1][9]

Return precautions (patient counseling)

• Return immediately for recurrent fever, dark urine, jaundice, confusion, shortness of breath, or inability to keep medications down
• Complete the full course of antimalarials even if feeling better
• Fever after travel to an endemic area — even months later — warrants repeat evaluation [9]
• Expected recovery: uncomplicated malaria typically improves within 48–72 hours of appropriate treatment; fatigue may persist for weeks

1. Diagnosis, Treatment, and Prevention of Malaria in the US: A Review. — Daily JP, Minuti A, Khan N. The Journal of the American Medical Association. 2022.

2. Malaria: Prevention, Diagnosis, and Treatment. — Shahbodaghi SD, Rathjen NA. American Family Physician. 2022.

3. Guidelines for the Prevention and Treatment of Opportunistic Infections in Adults and Adolescents With HIV. — Constance Benson, John Brooks, Shireesha Dhanireddy, et al Infectious Diseases Society of America; Office of AIDS Research Advisory Council (2025). 2025.

4. Malaria. — Poespoprodjo JR, Douglas NM, Ansong D, Kho S, Anstey NM. Lancet. 2023.

5. Malaria. — Daily JP, Parikh S. The New England Journal of Medicine. 2025.

6. Guidelines for the Prevention and Treatment of Opportunistic Infections in Children With and Exposed to HIV. — Bill G. Kapogiannis, Franklin Yates, Wei Li, et al Office of AIDS Research Advisory Council (2025). 2025.

7. Case 4-2024: A 39-Year-Old Man with Fever and Headache after International Travel. — Ryan ET, Succi MD, Paras ML, Klontz EH. The New England Journal of Medicine. 2024.

8. Malaria: A Focused Review for the Emergency Medicine Clinician. — Long B, MacDonald A, Liang SY, et al. The American Journal of Emergency Medicine. 2024.

9. Malaria. — Alison D. Ridpath and Erika Wallender CDC Yellow Book. 2025.

10. Indicators of Life-Threatening Malaria in African Children. — Marsh K, Forster D, Waruiru C, et al. The New England Journal of Medicine. 1995.