Initial symptoms of malaria usually begin a few days to several weeks after exposure to the parasite, but they can also appear up to a year later. Malaria is classified as either uncomplicated or severe. Severe or complicated malaria is a medical emergency that requires aggressive treatment. In most cases, malaria can be cured if it’s diagnosed and treated quickly, according to established medical guidelines. (1)
Incubation Period
Malaria has a delayed onset from time of exposure, known as an incubation period, that’s usually 7 to 30 days long. A short incubation period is typical for P. falciparum, the most common parasite variety in Africa and the deadliest form of the disease. P. malariae, found worldwide, tends to have a long incubation period. The onset of symptoms may be delayed beyond 30 days in people who take medicines to prevent malaria, as well as in people with frequent malaria exposure. In people who take drugs to prevent malaria, symptoms may develop weeks or even months after the usual incubation period. This can make it difficult for healthcare providers to screen for malaria in countries where it’s uncommon, like the United States. It’s important to remind your healthcare provider of any trips you took to an area where malaria was transmitted during the previous 12 months. (1)
Symptoms of Uncomplicated Malaria
The classic symptoms of malaria occur as attacks that last 6 to 10 hours. These attacks may recur every two or three days, depending in the specific parasite, and involve:
An initial stage of feeling cold and shiveringA second stage involving fever, headaches, and vomitingA third and final stage of sweating intensely and feeling tired
Most people, though, don’t experience symptoms that fit such a precise pattern. (1) Common symptoms of uncomplicated malaria include:
Fever, sweating, and chillsNausea and vomitingDiarrheaHeadache and body achesGeneral sense of illness or weakness (1,2)
Your healthcare provider (or, less commonly, you) may also observe:
An enlarged spleen or liverIncreased temperature, heart rate, or breathing rateMild jaundice (yellowing of your eyes and skin)
If you have any of the above symptoms and have been to an area where malaria is transmitted during the last 12 months, you should seek immediate medical care. (1)
Complications of Severe Malaria
In severe or complicated malaria, the infection leads to organ failure or abnormalities in your bloodstream or metabolism. (1) Many of these complications are due to infected red blood cells sticking to the inside of small blood vessels, creating blockages. (2) Some complications of severe malaria include: Cerebral Malaria This severe neurological complication occurs when infected red blood cells block blood vessels in your brain. It often first manifests as a seizure, and can progress rapidly to coma or death if left untreated. Cerebral malaria can cause abnormal behavior, impaired consciousness, or permanent neurological damage including blindness and deafness, especially in children. Hypoglycemia People with malaria may develop dangerously low blood sugar, especially pregnant women and children. This complication may be caused by malaria’s interference with the liver’s role in glucose storage, or by quinine, a drug used to treat the disease. Metabolic Acidosis This complication involves excessive acid in your blood and tissue fluids, and is often seen along with hypoglycemia. Pulmonary Edema In this complication, fluid accumulates in your lungs and can impair breathing. Acute Respiratory Distress Syndrome (ARDS) This inflammatory reaction in your lungs can lead to severe breathing difficulties. ARDS can develop even after your parasite count has gone down in response to treatment. Abnormalities in Blood Coagulation and Blood Pressure These complications may not be visible, but they can lead to tissue damage throughout your body. Hyperparasitemia This complication is defined as more than 5 percent of your red blood cells becoming infected with malaria parasites. Severe Anemia Destruction of red blood cells can lead to a low count of these cells. Organ Dysfunction Your liver or kidneys may fail, or your spleen may rupture. These problems can be acute (sudden) and life-threatening. (1,2)
Severe Malaria Risk Factors
Categories of people with the greatest risk for severe malaria infection include:
Pregnant womenInfantsYoung children (6 months to 3 years old)Travelers from areas without malariaPeople with immune system problems, including HIV/AIDSTravelers to sub-Saharan Africa, where the most dangerous form of malaria is widespread (1,2,3)
Children with severe malaria often experience hypoglycemia, metabolic acidosis, severe anemia, coma, convulsions, and cognitive developmental damage. Adults with severe malaria are more likely to develop severe jaundice, kidney failure, and pulmonary edema. (3)
Malaria Diagnosis
Malaria must be promptly recognized and treated to save an infected person’s life, and also to prevent the further spread of malaria. If your doctor suspects that you have malaria, you’ll need blood tests to check whether you have it and, if so, what kind you have. If possible, you should always have your diagnosis confirmed with a blood test before beginning treatment. (1) Blood tests can also detect signs of severe illness, such as anemia, metabolic acidosis, or liver or kidney problems. (2) Common blood tests for the malaria parasite include: Microscopic Diagnosis This test is widely considered the gold standard for laboratory confirmation of malaria. After your blood sample is stained and smeared on a microscope slide, experienced lab analysts can recognize the species of malaria and the percentage of red blood cells that have been infected. Rapid Diagnostic Tests (RDTs) These tests can provide results quickly, but they may not be as accurate as microscopic diagnosis. Some hospitals use RDTs for a preliminary result, then follow up with a microscopic confirmation. Molecular Diagnosis This process involves using polymerase chain reaction (PCR) tests to diagnose the species of malaria. Getting the results may take too long to help a patient who is acutely ill, so molecular diagnosis tends to be used only as a second step after a faster diagnostic test. Serology In some situations, your doctor may order tests that show whether you had malaria sometime in the past. Drug Resistance Tests These tests are used to make sure that your doctor gives you the right medicine to treat your malaria. In many areas of the world, malaria parasites have evolved to become resistant to certain drugs, so your treatment may need to be adjusted accordingly. (1,2)
