Malaria Surveillance - United States, 2015

Area of Science:

• Infectious Disease Epidemiology
• Public Health Surveillance
• Parasitology

Background:

• Malaria is transmitted by Anopheles mosquitoes and primarily affects travelers to endemic regions.
• In the U.S., malaria cases are mostly imported, but local transmission, congenital cases, and blood product exposure can occur.
• Surveillance is crucial for understanding malaria occurrence, guiding prevention, and controlling local transmission.

Purpose of the Study:

• To summarize confirmed malaria cases in the U.S. with symptom onset in 2015.
• To analyze trends in malaria cases and identify contributing factors.
• To assess antimalarial drug resistance and evaluate prevention measure adherence.

Main Methods:

• Data compilation from the National Malaria Surveillance System (NMSS) and National Notifiable Diseases Surveillance System (NNDSS).
• Diagnostic assistance and antimalarial drug resistance marker testing by CDC reference laboratories.
• Analysis of case investigations, travel history, and chemoprophylaxis use.

Main Results:

• 1,517 confirmed malaria cases reported in 2015, a decrease from 2014, largely due to fewer cases from West Africa.
• Plasmodium falciparum was the most common species (67.4%); 17.1% of cases were severe, and 11 deaths occurred.
• Chemoprophylaxis adherence was low (26.5% in 2015 vs. 32.5% in 2014), with 95.3% of U.S. residents not adhering to recommendations.

Conclusions:

• The decrease in cases may be linked to reduced travel to West Africa during the Ebola outbreak.
• Inadequate use of malaria prevention measures by travelers, particularly those visiting friends and relatives, persists.
• Enhanced surveillance, improved reporting completeness, and targeted prevention strategies are needed to reduce imported malaria cases.