CDC Operational Guidance for Investigating Locally Acquired Mosquito-Transmitted Malaria — United States, 2026

During 2023, 10 cases of locally acquired mosquito-transmitted (autochthonous) malaria were reported to CDC from four U.S. states after a 20-year period with no autochthonous cases.These cases highlight that although the United States eliminated malaria transmission in the early 1950s, the country remains susceptible to malaria reintroduction.This report provides operational guidance to local, state, tribal, territorial, and Federal public health responders on public health investigation and response to a suspected autochthonous malaria case in the United States.The guidance in this report updates the 2006 guidance (CDC.Locally acquired mosquito-transmitted malaria: a guide for investigations in the United States.Atlanta, GA: US Department of Health and Human Services, CDC; 2006) and is based on CDC subject-matter expertise, outbreak response experience from 2023, and targeted literature review.Investigations of suspected autochthonous malaria cases often raise public concern and can require substantial public health resources.Public health investigations of these cases should include epidemiologic, entomologic, and laboratory components and frequently require coordination among local, state, and Federal jurisdictions.This report provides an outline of the essential actions for such investigations conducted by describing the components of the investigation and providing resources and tools to assist public health personnel at the local, state, and Federal level.