Malaria Clinical Presentation

Updated: May 11, 2023
  • Author: William N Bennett, V, MD; Chief Editor: Michael Stuart Bronze, MD  more...
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In patients with suspected malaria, obtaining a history of recent or remote travel to an endemic area is critical. Asking explicitly if they traveled to a tropical area at any time in their life may enhance recall. Maintain a high index of suspicion for malaria in any patient exhibiting any malarial symptoms and having a history of travel to endemic areas.

Also determine the patient's immune status, age, and pregnancy status; allergies or other medical conditions that they may have; and medications that they may be using.

Patients with malaria typically become symptomatic a few weeks after infection, although the host's previous exposure or immunity to malaria affects the symptomatology and incubation period. In addition, each Plasmodium species has a typical incubation period. Importantly, virtually all patients with malaria present with headache. Clinical symptoms include the following:

  • Cough

  • Fatigue

  • Malaise

  • Shaking chills

  • Arthralgia

  • Myalgia

Patients experience a paroxysm of fever, shaking chills, and sweats (every 48 or 72 h, depending on species). The classic paroxysm begins with a period of shivering and chills, which lasts for approximately 1-2 hours and is followed by a high fever. Finally, the patient experiences excessive diaphoresis, and the body temperature of the patient drops to normal or below normal.

Many patients, particularly early in infection, do not present the classic paroxysm but may have several small fever spikes a day. Indeed, the periodicity of fever associated with each species (ie, 48 h for P falciparum, P vivax, and P ovale [or tertian fever]; 72 h for P malariae [or quartan fever]) is not apparent during initial infection because of multiple broods emerging in the bloodstream. In addition, the periodicity often is not observed in P falciparum infections. Patients with long-standing, synchronous infections are more likely to present with classic fever patterns. In general, however, the occurrence of periodicity of fever is not a reliable clue to the diagnosis of malaria.

Less common malarial symptoms include the following:

  • Anorexia and lethargy

  • Nausea and vomiting

  • Diarrhea

  • Jaundice

Notably, infection with P vivax, particularly in temperate areas of India, may cause symptoms up to 6-12 months after the host leaves the endemic area. Patients infected with P vivax or P ovale may relapse after longer periods, because of the hypnozoite stage in the liver.

P malariae does not have a hypnozoite stage, but patients infected with P malariae may have a prolonged, asymptomatic erythrocytic infection that becomes symptomatic years after leaving the endemic area.

Tertian and quartan fevers are due to the cyclic lysis of red blood cells that occurs as trophozoites complete their cycle in erythrocytes every 2 or 3 days, respectively. P malariae causes quartan fever; P vivax and P ovale cause the benign form of tertian fever; and P falciparum causes the malignant form. The cyclic pattern of fever is very rare.

Travelers to forested areas of Southeast Asia and South America have become infected by Plasmodium knowlesi, a dangerous species normally found only in long-tailed and pigtail macaque monkeys (Macaca fascicularis and M nemestrina, respectively). This species can cause severe illness and death in humans, but, under the microscope, the parasite looks similar to the more benign P malariae and sometimes has been misdiagnosed.

Because P malariae infection typically is relatively mild, Plasmodium knowlesi infection should be suspected in persons residing or traveling in the above geographic areas who are severely ill and have microscopic evidence of P malariae infection. Diagnosis may be confirmed via polymerase chain reaction (PCR) assay test methods.


Physical Examination

Most patients with malaria have no specific physical findings, but splenomegaly may be present. Symptoms of malarial infection are nonspecific and may manifest as a flulike illness with fever, headache, malaise, fatigue, and muscle aches. Some patients with malaria present with diarrhea and other gastrointestinal (GI) symptoms. Immune individuals may be completely asymptomatic or may present with mild anemia. Nonimmune patients may quickly become very ill.

Severe malaria primarily involves P falciparum infection, although death due to splenic rupture has been reported in patients with non– P falciparum malaria. Severe malaria manifests as cerebral malaria, severe anemia, respiratory symptoms, and renal failure.

In children, malaria has a shorter course, often rapidly progressing to severe malaria. Children are more likely to present with hypoglycemia, seizures, severe anemia, and sudden death, but they are much less likely to develop renal failure, pulmonary edema, or jaundice.

Cerebral malaria

This feature almost always is caused by P falciparum infection. Coma may occur; coma usually can be distinguished from a postictal state secondary to generalized seizure if the patient does not regain consciousness after 30 minutes. When evaluating comatose patients with malaria, hypoglycemia and CNS infections should be excluded.

Severe anemia

The anemia associated with malaria is multifactorial and usually is associated with P falciparum infection. In nonimmune patients, anemia may be secondary to erythrocyte infection and a loss of infected RBCs. In addition, uninfected RBCs are inappropriately cleared, and bone marrow suppression may be involved.

Renal failure

Renal failure is a rare complication of malarial infection. Infected erythrocytes adhere to the microvasculature in the renal cortex, often resulting in oliguric renal failure. Renal failure typically is reversible, although supportive dialysis often is needed until kidney function recovers. In rare cases, chronic P malariae infection results in nephrotic syndrome.

Respiratory symptoms

Patients with malaria may develop metabolic acidosis and associated respiratory distress, and pulmonary edema can occur. Signs of malarial hyperpneic syndrome include alar flaring, chest retraction (intercostals or subcostal), use of accessory muscles for respiration, or abnormally deep breathing.