Malaria is a life-threatening disease caused by Plasmodium parasites, transmitted to humans through the bites of infected female Anopheles mosquitoes. The parasite’s life cycle begins when it is injected into a person’s bloodstream, travels to the liver to mature, and then enters the bloodstream to infect red blood cells, initiating the symptomatic phase. The majority of cases and related deaths occur in the WHO African Region, and while the disease is preventable and curable, its initial symptoms can be mistaken for other illnesses. The Plasmodium falciparum species is responsible for the most severe forms of malaria and the majority of deaths.
The Initial Sickness
The first signs of malaria appear 10 to 15 days after an infected mosquito bite and often resemble the flu, making early recognition difficult. The illness begins with a combination of fever, headaches, muscle aches, nausea, and fatigue.
A defining characteristic of uncomplicated malaria is the cyclical pattern of symptoms known as a paroxysm. This cycle starts with a sudden feeling of intense cold, leading to shivering, followed by a period of high fever. The cycle concludes with intense sweating as the body’s temperature falls, often leaving the individual exhausted.
This recurring pattern is a direct consequence of parasites multiplying inside red blood cells. When these infected cells rupture in unison, they release new parasites and toxic waste into the bloodstream. The body’s immune system responds by producing cytokines, which trigger the fever and other symptoms. Depending on the specific Plasmodium species, these cycles can recur every 36-48 hours.
Progression to Severe Malaria
If uncomplicated malaria caused by P. falciparum is not treated promptly, it can advance to a severe stage with serious organ complications. The underlying cause of these failures is linked to the behavior of infected red blood cells, which become “sticky.” These cells adhere to the inner walls of small blood vessels, creating blockages that obstruct blood flow and starve vital organs of oxygen.
One of the most significant complications is severe anemia, which arises from the massive destruction of red blood cells. The bone marrow is often unable to produce new red blood cells fast enough to compensate, leading to weakness and an inadequate oxygen supply.
The disease can also cause acute organ damage. Acute kidney injury is a common development, as waste products from destroyed red blood cells can clog the kidneys’ filtering units. The liver is also frequently affected, leading to jaundice, a yellowing of the skin and eyes from an accumulation of bilirubin.
Neurological Consequences
The most severe neurological complication of malaria is cerebral malaria, almost exclusively caused by P. falciparum infections. This medical emergency is characterized by the onset of neurological symptoms, including confusion, disorientation, and a decreased level of consciousness that can rapidly progress to a coma or seizures.
The development of cerebral malaria stems from the same process that damages other organs. The “sticky” parasitized red blood cells obstruct blood flow in the brain, leading to reduced oxygen supply, inflammation, and potential brain swelling.
While prompt treatment can be lifesaving, survivors, particularly children, face an increased risk of long-term neurological and cognitive deficits. These can include difficulties with memory, motor impairments, and the development of epilepsy months or years after the illness.
Chronic and Recurring Malaria
Beyond the acute illness, malaria can persist in the body, leading to chronic issues and recurrent episodes of sickness. This is particularly true for infections caused by Plasmodium vivax and Plasmodium ovale. These two species create dormant parasite forms, called hypnozoites, that remain in the liver for months or even years after the initial infection has been treated.
The reactivation of these dormant liver-stage parasites causes a relapse, where the individual experiences a new bout of malaria without being bitten again. This phenomenon is different from recrudescence, which is a resurgence of symptoms from a low level of parasites remaining in the bloodstream, a characteristic that can occur with P. falciparum infections.
Chronic or repeated malaria infections can also lead to an enlarged spleen (splenomegaly) and persistent, low-grade anemia.
Vulnerable Populations
While malaria can affect anyone, its impact is disproportionately severe in certain vulnerable groups, primarily young children and pregnant women. These populations are more susceptible to the disease’s worst outcomes due to immunological and physiological factors.
Children under the age of five are at the highest risk for severe malaria and death. Having not yet developed sufficient partial immunity from previous infections, their bodies are less equipped to control the parasite’s proliferation. This lack of acquired immunity means the disease can progress rapidly to severe anemia and cerebral malaria.
Pregnant women also face heightened risks. Changes in their immune system during pregnancy make them more susceptible to infection and severe complications. A dangerous form is placental malaria, where parasites accumulate in the placenta, interfering with the transfer of nutrients and oxygen to the fetus. This can lead to maternal anemia, miscarriage, stillbirth, or delivering a baby with low birth weight.