As of April 18, 2025, a total of 2,318 cases of measles have been reported in six countries in the World Health Organization (WHO) Americas region, including three deaths. Compared with 205 cases in the same period of 2024, the number of cases has soared by 11 times. Most cases occurred among people aged 1 to 29, who were either unvaccinated or had an unknown immunization status. Furthermore, the majority of cases are related to imports or associated with imports. Measles is a highly contagious airborne viral disease that can lead to serious complications and even death. Although it can be prevented by two doses of the vaccine, in 2023, more than 22 million children worldwide still did not receive the first dose of the vaccine, leading to an increase in global measles cases in 2024 and a rising risk of imported infections. The World Health Organization is working closely with countries in the Americas region to prevent the spread and reintroduction of measles. At present, the risk in this region is assessed as high, while the global risk remains moderate.
Overview of Measles Epidemics in Various Countries
From January 1 to April 18, 2025, a total of 2,318 cases of measles were reported in the Americas region, involving six countries: Argentina, Belize, Brazil, Canada, Mexico and the United States.
Argentina
From January 1 to April 16, 2025, Argentina reported 21 confirmed cases of measles, among which 3 were imported cases, 13 were related to imported cases, and 5 were still under investigation. The first case was a child with an international travel history, reported on January 31, 2025. As of April 16th, another 19 cases have been confirmed, with ages ranging from 5 months to 40 years old. Among them, 2 cases had international travel records, and only 2 cases required hospitalization due to pneumonia.
Belize
On April 12, 2025, Belize confirmed two positive cases of measles, the first since 1991. The two 17-year-old male patients, who had no vaccination history, went to Chihuahua, Mexico to attend a religious gathering from January 5th to March 31st, 2025. The symptoms emerged on April 2nd and April 3rd. Despite Belize’s efforts to increase vaccination coverage, it still falls below the target range of 92-95%.
Brazil
From January 1 to April 18, 2025, Brazil reported five confirmed cases of measles at four locations. Two of the cases were children under one year old and neither had a history of vaccination. The cases in the Federal District and Rio Grande do Sul were adults with an international travel history. Sao Paulo reported one adult case with a vaccination history but no international travel history.
Canada
From January 1 to April 12, 2025, Canada reported 1,069 confirmed and suspected cases of measles from seven provinces. These cases far exceed the 177 cases reported in 2024. Most cases are related to large-scale multi-jurisdictional outbreaks that occur in undervaccinated communities. This epidemic was triggered by an international imported case who attended a large gathering in New Brunswick in October 2024.
Mexico
From January 1 to April 16, 2025, Mexico confirmed 421 cases of measles, including 2 imported cases, 35 cases related to imports, and 384 cases under investigation. The first confirmed case was an unvaccinated child with an international travel history. Later, another 419 cases were confirmed, most of which occurred among people aged 25 to 44.
The United States
As of April 17, 2025, a total of 800 confirmed cases of measles have been reported in 25 jurisdictions of the United States, including 2 deaths. 93% of the cases were related to the epidemic, and the epidemics in Texas, New Mexico and Oklahoma accounted for 82% of the reported cases. The vast majority of cases have not been vaccinated or their vaccination status is unknown. 11% of the cases require hospitalization, among which 19% are children under the age of 5.
Epidemiological Summary
The risk of measles transmission in the Americas remains high, especially among those who have not been vaccinated or whose vaccination status is unknown. The World Health Organization calls on all countries to enhance vaccination efforts to prevent the further spread of measles.
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