US, Mexico and Guatemala risk losing their measles-free status

International health experts are meeting in Washington, DC, this week to determine whether the United States, Mexico and Guatemala retain their measles elimination status.

The Pan American Health Organization's (PAHO) Regional Monitoring and Re-Verification Commission (RVC) began its annual conference on Tuesday, and the conference will adjourn on Friday. The commission will review reports submitted by all 35 PAHO member states, with particular attention to countries experiencing prolonged outbreaks.

Measles elimination status is a designation that the virus has not spread uncontrolled domestically for at least 12 months. The Americas became the first region in the world to eliminate endemic measles transmission in 2016. This year's review is examining epidemiological data from 2025 and the first half of 2026.

The US has held its elimination status since 2000, but it risks losing it this year. The US has experienced sustained outbreaks since January 2025, in its largest and deadliest measles outbreak in nearly 30 years. Mexico has also reported prolonged transmission.

PAHO reported 57,666 confirmed measles cases across 17 countries and territories in the Americas between January and October 2026. Besides the US, Mexico and Guatemala, Peru and Bolivia are also at risk. Canada lost its status last November.

Reported cases or deaths alone do not determine whether a country loses its status. Some cases come from exposure during travel, and a limited outbreak from such exposure would not result in loss of status. Under PAHO's criteria, a country loses its elimination status if the same measles virus strain continues to spread uninterrupted for at least 12 months in a country or defined geographical area.

Investigators use genetic sequencing to determine whether infections are linked to the same virus strain. The commission also considers vaccination coverage, how healthcare systems monitor measles cases, and the speed of outbreak responses.

The RVC is an independent panel of international experts in epidemiology, public health and virology that advises PAHO, which is part of the World Health Organization. It will make recommendations to PAHO Director Jarbas Barbosa, who will make the final determination. The official announcement is expected early next week following the conclusion of the conference.