When symptoms appear

The time from the initial malaria infection until symptoms appear (incubation period) generally ranges from:¹

• 9 to 14 days for Plasmodium (P.) falciparum.
• 12 to 18 days for P. vivax and P. ovale.
• 18 to 40 days for P. malariae.

Symptoms can appear in 7 days. Occasionally, the time between exposure and signs of illness may be as long as 8 to 10 months with P. vivax and P. ovale.

The incubation period may be longer if you are taking medicine to prevent infection (chemoprophylaxis) or because you have some immunity due to previous infections.

Variation in symptoms

In regions where malaria is present, people may have the disease but-due to immunity or semi-immunity-they have few or no symptoms.² The severity of malaria symptoms can also vary depending on your immunity, your general health, and whether you still have your spleen.

Common symptoms of malaria

In the early stages, malaria symptoms are sometimes similar to those of many other infections caused by bacteria, viruses, or parasites. Symptoms may include:

• Fever.
• Chills.
• Headache.
• Sweats.
• Fatigue.
• Nausea and vomiting.

Symptoms may appear in cycles and may come and go at different intensities and for different lengths of time. However, especially at the beginning of the illness, the symptoms may not follow this typical pattern.

The cyclic pattern of malaria symptoms is due to the life cycle of malaria parasites as they develop, reproduce, and are released from the red blood cells and liver cells in the human body. This cycle of symptoms is also one of the major indicators that you are infected with malaria.

Other common symptoms of malaria

Other common symptoms of malaria include:

• Dry (nonproductive) cough.
• Muscle and/or back pain.
• Enlarged spleen.

Rarely, malaria can lead to impaired function of the brain or spinal cord, seizures, or loss of consciousness.

Infection with the P. falciparum parasite is usually more serious and may become life-threatening.

There are other conditions with symptoms similar to a malarial infection. It is important that you see your doctor to discover the cause of your symptoms.