Malaria is a mosquito-borne disease caused by parasites of the Plasmodium genus, transmitted to humans through the bite of infected female Anopheles mosquitoes. It remains a global public health concern, especially in tropical and subtropical regions, where nearly half the world’s population is at risk. In 2022, there were an estimated 249 million cases of malaria worldwide, resulting in approximately 608,000 deaths.
Typical Manifestations
The initial symptoms of malaria can resemble a flu-like illness. These symptoms usually appear 10 to 15 days after an infective mosquito bite. Common signs include fever, chills, headache, muscle aches, and fatigue. Patients may also experience nausea, vomiting, and diarrhea.
Some individuals experience a malarial paroxysm, a cyclical pattern of symptoms. This paroxysm involves three stages: a cold stage (15-60 minutes) with shivering and intense cold; a hot stage (2-6 hours) with high fever, flushed skin, headache, and nausea; and a sweating stage (2-4 hours) where fever drops and profuse sweating occurs, causing extreme fatigue. The periodicity of these fevers can vary by parasite species; for instance, Plasmodium vivax and P. ovale infections often lead to fevers every 48 hours, while P. malariae can cause fevers every 72 hours.
Life-Threatening Complications
Untreated or rapidly progressing malaria, especially that caused by Plasmodium falciparum, can lead to severe complications. These complications can develop quickly, sometimes within hours or days, and may involve multiple organ systems. Cerebral malaria, a severe neurological manifestation, involves parasite-filled red blood cells blocking small blood vessels in the brain, potentially leading to swelling, seizures, and coma, and can result in significant brain damage.
Severe anemia is a common complication, resulting from the destruction of red blood cells by the parasites and impaired red blood cell production in the bone marrow. Acute kidney injury can also occur, ranging from mild proteinuria to severe renal failure. The kidneys may become impaired due to microcirculatory compromise and reduced tissue oxygenation.
Acute Respiratory Distress Syndrome (ARDS) is a severe inflammatory reaction in the lungs that hinders oxygen exchange, potentially occurring even after parasite counts decrease. Hypoglycemia, or low blood sugar, is another metabolic complication that can be difficult to recognize as its symptoms often mimic other signs of severe malaria. Circulatory collapse or shock, characterized by very low blood pressure, can develop, sometimes in conjunction with coexisting bacterial infections. While less common, splenic rupture is a complication, particularly associated with P. vivax infection, where the enlarged spleen becomes fragile and susceptible to trauma.
Specific Vulnerabilities
Malaria disproportionately affects certain populations, particularly young children and pregnant women, due to their physiological vulnerabilities. Children under five years of age are at a higher risk of developing severe malaria. In 2023, children under five accounted for approximately 76% of all malaria deaths in the WHO African Region. Their developing immune systems are less equipped to combat the parasitic infection, making them more susceptible to severe anemia, respiratory distress linked to metabolic acidosis, and cerebral malaria.
Pregnant women also face increased risks from malaria, which can impact both the mother and the developing fetus. Malaria during pregnancy can lead to severe anemia in the mother, increasing her risk of death. For the fetus, maternal malaria can result in adverse outcomes such as stillbirth, premature birth, and low birth weight. An estimated 872,000 children were born with a low birth weight in 2018 due to malaria in pregnancy. Congenital malaria, where the infection is transmitted from mother to unborn child, is also a potential consequence.
Long-Term Consequences
Even after recovering from acute malaria, individuals can experience lasting health effects. Persistent fatigue and general weakness are common post-malaria symptoms. Children who have suffered from cerebral malaria are at risk for long-term neurological and cognitive impairments, including developmental delays, learning disabilities, and issues with motor skills, visual coordination, and attention. These impairments can profoundly affect their quality of life.
Chronic anemia can persist following malaria, contributing to ongoing weakness and reduced overall health. Recurrent malaria infections are a concern, especially with P. vivax and P. ovale, which can form dormant liver stages (hypnozoites) that reactivate and cause relapses months or even years after the initial infection. Tropical Splenomegaly Syndrome, also known as hyperreactive malarial splenomegaly, can develop after repeated infections, leading to a massively enlarged spleen and liver, abnormal immune responses, and increased susceptibility to other infections. In severe cases, long-term organ damage, particularly to the kidneys and liver, can occur, potentially leading to chronic renal impairment or other functional limitations.