Malaria is a protozoan infection. Anopheline mosquitoes release sporozoites into the blood. The sporozoites infect human hepatocytes. The hepatocytes release merozoites into the blood 1-2 weeks later. Malarial paroxysms are the invasion and rupture of red blood cells by these merozoites.

1,724 (US); 216,000,000 (Global)
Plasmodium falciparum; P. vivax; P. ovale; P. malariae; P. knowlesi;
9 days to 2 weeks (P. falciparum); 12-18 days (P. vivax & P. ovale); 18-40 days (P. malariae); Some strains of P. vivax from temperate areas: 8-10 months; [CCDM, p. 374]
Headache, fatigue & myalgias followed by fever; "Febrile paroxysms at regular intervals are unusual and suggest infection with P. vivax or P. ovale." [Harrisons, p. 611] Rash or lymphadenopathy suggests another cause of the fever. [Cecil, p. 2078]
Anopheline mosquitoes bite at night and release sporozoites into the blood. The sporozoites infect human hepatocytes. One to three weeks later, the hepatocytes release merozoites into the blood. Malarial paroxysms are associated with the invasion and rupture of red blood cells by these merozoites. Paroxysms are marked by fever, chills, headache, and nausea followed by profuse sweating. Other findings that may occur in all forms of malaria are anemia, jaundice, splenomegaly, and hepatomegaly. For P. vivax and P. ovale, infected hepatocytes can rest in a latent stage for 2-3 years. [Merck Manual, p. 1551-3] In one series of 160 patients in a travel clinic, symptoms were as follows: fever (100%), headache (100%), weakness/fatigue (94%), night sweats (91%), arthralgias (59%), myalgias (56%), diarrhea (13%), and abdominal pain (8%). The classic paroxysm lasts several hours and includes chills followed by high fever, then profuse sweating, and finally extreme fatigue and sleep. [PPID, p. 3310] As a general rule, uncomplicated malaria does not cause lymphadenopathy, pharyngitis, rash, or pulmonary consolidation. [Cohen, p. 1018; PPID, p. 3310] Variable or poor performance of RDT (Rapid Diagnostic Testing) for malaria species other that Plasmodium falciparum; [CDC Travel, p. 623]

The WHO criteria for severe malaria are any one of the following: cerebral malaria, respiratory distress, prostration, hyperparasitemia, severe anemia, hypoglycemia, jaundice, renal insufficiency, hemoglobinuria, shock, cessation of eating and drinking, repeated vomiting, and hyperpyrexia. P. falciparum can cause pulmonary edema and ARDS by sequestering in the tiny veins and capillaries of the lungs. Therefore, dyspnea is a finding in severe malaria. The urine may have the dark color of hemoglobinuria (black water fever) rather than the red color of hematuria. [PPID, p. 3311-12] Patients with P. falciparum malaria usually present within 4-6 weeks of their return from an endemic area. The fever pattern in falciparum malaria is "hectic." Cough and dyspnea are present in fewer than 20% of patients. Splenomegaly is present in about 25% of cases. Even less common are jaundice, abdominal pain, and hepatomegaly. Urticarial rash is rare. The WBC count is usually normal or slightly low (high in 5% of cases). Kidney function tests are usually normal at the time of presentation in the clinic. [ID, p. 2295] Inadequately treated patients with falciparum malaria may develop severe malaria: acute encephalopathy and coma, convulsions, renal failure, jaundice, pulmonary edema, bleeding diathesis, and shock. The other three malarias do not usually cause life-threatening disease. [CCDM, p. 372] Symptoms of cerebral malaria include deviated eyes, salivation, irregular breathing, opisthotonus, seizures, and coma. Complications, more common in children, include paralysis, aphasia, cerebellar ataxia, and cortical blindness. [Cohen, p.1019] Thrombocytopenia is commonly seen in malaria. [Wallach, p. 1200] Secondary pneumonia is a complication. Less than 5% of patients with severe malaria have bleeding complications including hematemesis. [Guerrant, p. 671, 656]
Microscopic examination of blood smears by expert is most sensitive method. Rapid diagnostic tests (RDTs) for HRP-2 or pLDH have high sens. & spec. [PPID] "Both positive and negative RDT results must always be confirmed by microscopy." [CDC Travel]
Large areas of Africa, Central and South America, Hispaniola, Asia (Middle East & South/Southeast Asia), Eastern Europe, and South Pacific; [CDC Travel]
  • >arthralgia
  • >fatigue, weakness
  • >fever
  • >fever, biphasic or relapsing
  • >myalgia
  • E pharyngitis
  • G abdominal pain
  • G diarrhea
  • G hematemesis
  • G hepatomegaly
  • G jaundice
  • G liver function test, abnormal
  • G nausea, vomiting
  • H anemia
  • H hemolysis
  • H hypergammaglobulinemia
  • H leukocytosis
  • H leukopenia
  • H splenomegaly
  • H thrombocytopenia
  • N confusion, delirium
  • N headache
  • N lethargy
  • N opisthotonus
  • N seizure
  • R chest pain
  • R cough
  • R dyspnea
  • S urticaria
  • U hematuria
  • X lung infiltrates
  • *acute renal failure
  • *ARDS
  • *bleeding tendency
  • *blindness
  • *glomerulonephritis
  • *myelitis
  • *paralysis
  • *pneumonia
  • *pulmonary edema
  • *sepsis
  • *shock
  • *stupor, coma




Needle (Includes Drug Abuse), Scalpel or Transfusion
Monkeys, Human
  • Asplenic patients
  • Have a blood transfusion
  • Injection drug users
  • Travel to endemic area
CDC Malaria Hotline: 770-488-7788 or 770-488-7100 (after hours);
1. (US) About 1500 cases/yr in the US, almost all acquired abroad; A few cases from blood transfusions and rare autochthonous (transmission by local mosquitoes that have bitten infected immigrants); [Merck Manual, p. 1551] Published in MMWR 2011: 1,724 cases;
2. (Global) 627,000 deaths in 2012, mostly in African children; Death rates have decreased 45% since 2000; [Fact sheets from WHO 2013] About 216 million cases/year; [CDC Travel, p. 267]