Healthcare-Associated Transmission of Plasmodium falciparum Malaria in Westchester County, NY, 2023

Overview

A 65-year-old Westchester County resident was diagnosed with Plasmodium falciparum malaria without recent international travel, prompting an extensive epidemiological and genetic investigation. Findings implicated healthcare-associated blood-borne transmission from a hospitalized traveler with malaria, with no evidence of mosquito-borne transmission or additional cases.

Background

Malaria was declared eliminated in the United States in 1951, with certification as malaria-free in 1970. Most US cases are travel-associated, but rare locally acquired cases occur via mosquito transmission or other routes such as blood transfusion or breaches in infection control. In 2023, several states reported locally acquired mosquito-transmitted malaria cases, the first since 2003. New York's last locally acquired case was hospital-associated in 2012. This report details the first locally acquired malaria case in New York since then and the subsequent public health investigation.

Data Highlights

The patient presented with 16.8% parasitemia confirmed by blood smear and PCR. Mosquito surveillance was conducted from June to September 2023, with no Anopheles species linked to transmission identified near the patient's residence. Geospatial mapping of travel-associated malaria cases within a 5-mile radius of the patient's home and workplace was performed to assess mosquito transmission risk. Genetic analysis of specimens from the patient and epidemiologically linked cases confirmed healthcare-associated transmission.

Key Findings

• The patient had no recent international travel but had hospitalizations overlapping with a traveler diagnosed with malaria.
• Genetic and epidemiologic investigations implicated blood-borne transmission in a healthcare setting, likely due to infection control lapses.
• No mosquito-transmitted malaria cases were identified in New York during the investigation period.
• No additional induced or healthcare-associated malaria cases were detected following the index case.
• Mosquito surveillance and geospatial analysis did not support local mosquito-borne transmission.
• Prompt identification and investigation facilitated targeted control measures to prevent further cases.

Clinical Implications

Clinicians should consider malaria in febrile patients without travel history, especially with recent healthcare exposures. Strict adherence to infection prevention protocols is critical to prevent healthcare-associated malaria transmission. Public health surveillance and rapid epidemiological investigations are essential to identify transmission sources and mitigate risks of local spread.

Conclusion

This case represents a rare healthcare-associated Plasmodium falciparum malaria transmission in New York, highlighting the importance of vigilance for non-travel-related malaria and robust infection control practices to prevent nosocomial transmission.

References

1. CDC/US Malaria Elimination History/1951-1970
2. New York State Department of Health/2012 Malaria Case Report
3. Westchester County Department of Health/2023 Malaria Investigation