Malaria

What malaria is

Malaria is caused by single-celled parasites. When an infected female Anopheles mosquito bites, usually between dusk and dawn, it injects parasites into the blood. They travel to the liver, multiply silently for about a week or longer, then burst out and invade red blood cells. Inside the red cells they multiply again, rupture the cells and infect new ones. Each cycle of rupture releases toxins that cause fever and chills.

Worldwide, the WHO reports more than 240 million cases and around 600,000 deaths a year, mostly young children in Africa. In the US, about 2,000 cases are diagnosed each year, almost all in travelers and immigrants returning from affected countries. Local spread in the US is very rare but has occurred.

Malaria does not spread person to person through casual contact. It can rarely spread through blood transfusion, organ transplant, shared needles or from mother to baby during pregnancy.

Types of malaria

Malaria symptoms

Symptoms usually start 7 to 30 days after the infective bite. They can be delayed beyond that in people who took prevention tablets, and vivax or ovale malaria can appear for the first time up to a year or more after travel.

Early symptoms resemble flu:

• fever, often high and coming in waves
• shaking chills followed by heavy sweating
• headache
• muscle and joint aches, back pain
• tiredness and weakness
• nausea, vomiting, diarrhea and abdominal pain
• cough

The textbook pattern of fevers every 48 or 72 hours is uncommon, especially early on, and its absence does not rule malaria out. Children may simply be feverish, irritable, sleepy or off their food.

Severe malaria

Severe malaria is a medical emergency, mostly from P. falciparum. Signs include:

• confusion, abnormal behavior, seizures or coma (cerebral malaria)
• severe anemia, causing pale skin, breathlessness and weakness
• jaundice (yellow skin and eyes)
• kidney failure, with dark urine and reduced urine output
• low blood sugar, especially in children and pregnancy
• breathing difficulty from fluid in the lungs or acid buildup
• shock and abnormal bleeding

Who is at highest risk

• Travelers without immunity, including people born in malaria areas who now live abroad and return to visit friends and relatives. This group accounts for most US cases and often skips prevention.
• Young children and pregnant people, in whom malaria can cause severe disease, miscarriage, low birth weight and stillbirth.
• People without a spleen or with weak immune systems.

Some inherited conditions offer partial protection against severe falciparum malaria, including sickle cell trait, which is one reason the trait is common in malaria regions.

Diagnosis

Malaria cannot be diagnosed from symptoms alone because it looks like flu, dengue fever, typhoid fever and many other infections. Tell your doctor exactly where and when you traveled.

• Thick and thin blood smears: blood is examined under a microscope to confirm parasites, identify the species and measure the percentage of infected red cells. If the first smear is negative, it is repeated every 12 to 24 hours for a total of 3 sets.
• Rapid diagnostic tests (RDTs): detect parasite proteins within about 15 minutes. A positive or negative RDT is confirmed with a smear.
• PCR: confirms species in reference labs.
• Other blood tests: blood count, platelets, kidney and liver tests, glucose and lactate to judge severity.

Treatment

Treatment depends on the species, how severe the illness is, where the infection was caught (because of drug resistance) and whether the person is pregnant.

Uncomplicated malaria

• Artemisinin-based combination therapy (ACT) such as artemether-lumefantrine is the main treatment for falciparum malaria. Atovaquone-proguanil is an alternative.
• Chloroquine still works for vivax, ovale and malariae acquired in some regions, but resistance is widespread.
• People with falciparum malaria who have not been to malaria areas before are often admitted to hospital at first, because they can deteriorate quickly.

Severe malaria

IV artesunate is the treatment of choice. It is followed by a full course of oral treatment. Supportive care can include ICU monitoring, blood transfusion, treatment of low blood sugar and seizures, and dialysis.

Preventing relapse

For vivax and ovale malaria, an additional medicine, primaquine or tafenoquine, kills the dormant liver forms. A G6PD deficiency test must be done first, because these drugs can destroy red blood cells in people with that condition.

Complications

• cerebral malaria with lasting brain injury in some survivors, especially children
• severe anemia and hemolytic anemia
• acute kidney injury and acute respiratory distress syndrome
• spleen enlargement and, rarely, rupture
• in pregnancy: miscarriage, preterm birth, low birth weight and maternal death

Malaria prevention

Use the ABCD approach:

• Awareness of risk: check whether your destination has malaria and which species, using CDC or national travel advice.
• Bite prevention: use EPA-registered repellents such as DEET (20% to 50%) or picaridin, wear long sleeves and pants at dusk and night, sleep under an insecticide-treated bed net, and stay in screened or air-conditioned rooms.
• Chemoprophylaxis (prevention tablets): options include atovaquone-proguanil, doxycycline, mefloquine, tafenoquine and, in a few regions, chloroquine. The choice depends on destination, length of trip, other medicines, pregnancy and side effects. Start and stop exactly as directed, often continuing after you return.
• Diagnosis: seek testing promptly for any fever during or after travel, even if you took tablets.

No prevention method is 100% effective. Two malaria vaccines, RTS,S and R21, are used for young children in high-risk African regions. They are not currently available for travelers.

Frequently asked questions

What are the first signs of malaria?

The first signs are usually fever, chills, sweating, headache and muscle aches, often with nausea or vomiting. It feels like flu. Anyone with these symptoms during or after a trip to a malaria area should get a same-day malaria blood test.

How long after a mosquito bite do malaria symptoms start?

Most people develop symptoms 7 to 30 days after being bitten. Falciparum malaria usually appears within a month of return. Vivax and ovale malaria can appear months later, and occasionally more than a year later, because the parasite can lie dormant in the liver.

Can malaria be cured?

Yes. Malaria is curable with the right medicines, especially when treated early. Severe falciparum malaria can be fatal even with treatment, so speed matters. Vivax and ovale need an extra drug to clear dormant liver parasites and prevent relapse.

Is malaria contagious between people?

No. You cannot catch malaria from someone by touching, coughing or sexual contact. It spreads through infected mosquito bites. Rarely, it passes through blood transfusions, organ transplants, shared needles or from a pregnant person to their baby.

Do I still need malaria tablets if I grew up in a malaria country?

Yes. Partial immunity fades within months to a few years of living elsewhere. People visiting friends and relatives make up most travel-related malaria cases and deaths. Get prevention tablets and use bite prevention before every trip.

What is the difference between malaria and dengue?

Both cause fever after tropical travel and are spread by mosquitoes, but by different species. Dengue is a virus with severe body and eye pain and often a rash, and has no specific cure. Malaria is a parasite treated with antimalarial drugs. Only blood tests can reliably tell them apart.