Malaria - Overview

Malaria is a severe metabolic disease caused by unicellular parasites, primarily transmitted through the bites of infected female mosquitoes. This disease is widespread in tropical and subtropical regions worldwide, especially in African, Asian, and Central and South American countries, posing significant public health challenges. According to the World Health Organization, approximately 200 million confirmed cases are diagnosed annually, most of which occur in children.

The core pathogen of this disease is Plasmodium falciparum, whose complex life cycle involves interactions between humans and mosquitoes. In recent years, due to climate change and increased population mobility, the spread of malaria is expanding, making prevention and treatment critical global health issues. Understanding its transmission routes, symptom characteristics, and control strategies is vital for reducing infection risks.

Causes and Risk Factors

The transmission cycle of malaria involves three key components: infected mosquito vectors, human hosts, and the biological features of the parasite. When an infected female mosquito bites a human, the sporozoites in its saliva directly enter the bloodstream. These sporozoites then invade liver cells for replication, forming infectious erythrocytic stages.

High-risk groups include:

• Individuals residing in or traveling to endemic areas
• Children and the elderly with weakened immune systems
• Immunocompromised groups such as HIV/AIDS patients
• Residents in remote areas lacking mosquito prevention facilities

Environmental factors such as high temperature, humidity, and dense mosquito breeding sites also exacerbate disease transmission.

Symptoms

Typical symptoms usually appear within 7-30 days after infection, initially resembling influenza, including periodic fever, chills, and headache. Subsequently, severe symptoms such as splenomegaly, anemia, and liver and kidney dysfunction may develop. Infection with P. falciparum can lead to cerebral malaria, causing coma and neurological damage.

The manifestations vary significantly among different parasite species:

• Benign tertian malaria (P. vivax): periodic fever with splenomegaly
• Quartana malariae (P. malariae): low-grade fever and muscle pain
• Ovale malaria (P. ovale): incubation period can last several years

Severe cases may present with complications such as pulmonary edema and metabolic acidosis.

Diagnosis

The diagnostic process includes three stages: clinical assessment, laboratory testing, and molecular diagnosis. The first-line diagnostic methods are thin and thick blood smear staining to confirm parasite density and species. New PCR testing can improve early detection rates.

In special cases, the following are required:

1. Differential diagnosis: distinguishing from dengue fever, typhoid, and other febrile illnesses
2. Pregnant women require specific antiparasitic resistance testing
3. Severe cases should undergo blood biochemistry and imaging examinations

Diagnostic results should be combined with epidemiological history and laboratory evidence to ensure accurate treatment planning.

Treatment Options

Treatment strategies are tailored based on the parasite species and severity of infection. Mild cases are often treated with Artemisinin-based combination therapy (ACT), such as artesunate combined with mefloquine. Severe cases require immediate intravenous therapy and intensive care monitoring.

Drug selection should consider resistance patterns:

• Southeast Asia requires multi-drug combination regimens
• Most regions in Africa still prefer ACT as the first choice
• Cerebral malaria requires adjunctive corticosteroids and intracranial pressure management

Post-treatment, a 14-day follow-up is necessary to confirm parasite clearance.

Prevention

Comprehensive prevention includes personal protection, environmental control, and chemoprophylaxis. Travelers to endemic areas are advised to use DEET-containing repellents and sleep under insecticide-treated nets. Installing window screens and indoor residual spraying can effectively reduce vector mosquito populations.

Specific groups should undergo chemoprophylaxis:

• Travelers to high-risk areas should take doxycycline or atovaquone-proguanil
• Pregnant women should use the gold standard of mosquito nets
• In high transmission areas, intermittent preventive treatment (IPT) is recommended

Vaccination (RTS,S/AS01) provides about 30% protection in children and should be combined with other measures.

When Should You See a Doctor?

If you develop unexplained fever, periodic chills, or jaundice after returning from endemic areas, seek medical attention immediately and inform healthcare providers of your travel history. Signs of severe illness include altered consciousness, difficulty breathing, or severe anemia, which require emergency treatment.

Special groups should be particularly vigilant:

• Pregnant women with fever should be considered an emergency
• Children with a fever over 39°C accompanied by seizures
• Immunocompromised patients with rapid symptom progression

Delayed treatment may lead to fatal complications such as renal failure and metabolic acidosis.

 

Frequently Asked Questions

Does a fever after traveling to a malaria-endemic area necessarily mean malaria infection?

Fever is a typical symptom of malaria but not the only cause. If you develop fever, chills, or headache within a few weeks after staying in an endemic area, seek medical attention immediately and inform your travel history. However, other infections such as influenza or dengue fever can also cause similar symptoms; laboratory testing is necessary to confirm malaria.

Can using mosquito nets and repellents completely prevent malaria?

While mosquito nets and DEET-based repellents significantly reduce the risk of infection, they cannot provide complete protection. It is recommended to combine multiple preventive measures, such as wearing long-sleeved clothing, using indoor insecticides, and taking prophylactic antimalarial medications as prescribed, for optimal protection.

Is it possible to get malaria again after treatment?

Recovery from malaria does not confer lasting immunity, and reinfection is possible when traveling to endemic areas again. Continue mosquito prevention measures after treatment and avoid stopping medication prematurely. Even if symptoms disappear, complete the full course to prevent parasite resistance.

Which urban or town areas still pose a risk of malaria transmission?

Malaria is not limited to rural areas; some tropical cities in Africa or Asia may still have transmission if mosquito breeding environments exist. Check local epidemic information before traveling and follow health authorities’ prevention guidelines.

Why do some regions require long-term medication for malaria treatment?

Malaria parasites may reside in the liver stage, and some antimalarial drugs need to be used in stages to completely eradicate the parasites. For example, primaquine must be taken for several days to eliminate dormant hypnozoites and prevent relapse. Treatment plans should be adjusted by physicians based on the parasite type and regional drug resistance patterns.