WHO Disease Outbreak News | 27 March 2025
On 11 March 2025, the World Health Organization (WHO) received a report from the International Health Regulation (2005) (IHR) National Focal Point (NFP) of the United States of America (United States) on the ongoing measles outbreak in the country, notified under IHR because it is an unusual event with potential significant public health impact, with the number of cases and deaths in 2025 exceeding the numbers in previous years. Additionally, cases linked to the outbreak in the State of Texas, United States, have been reported in Mexico.
In 2000, measles was declared eliminated in the United States, since then imported cases of measles have been detected in the country, as the disease remains endemic in many parts of the world. WHO is working closely with countries in the WHO Region of the Americas to prevent the spread and reintroduction of measles.
On 11 March 2025, the NFP of the United States notified to WHO an ongoing outbreak of measles in the United States.
From 1 January to 20 March 2025, 378 cases have been reported from 17 States including: Alaska, California, Florida, Georgia, Kansas, Kentucky, Maryland, Michigan, New Jersey, New Mexico, New York State, Ohio, Pennsylvania, Rhode Island, Texas, Vermont, and Washington. Two deaths have also been reported, one confirmed in Texas and one under investigation in New Mexico. The majority of cases are in children who are unvaccinated or have unknown vaccination status. The hospitalization rate is 17%.
Ninety percent of the 378 cases (341 cases) have been associated with three distinct outbreaks (defined as three or more related cases) reported in 2025, while the remainder are sporadic cases that are part of the larger outbreak.
From 1 January 2025 to 20 March 2025, the US CDC reported 128 measles DNA sequences. Texas submitted 92 identical DNA sequences in genotype D8; while 10 DNA sequences from New Mexico and one DNA sequence from Kansas were identical to those from Texas. Texas also reported three genotype D8 sequences (a total of 19 D8 sequences have been reported from the affected States) with single nucleotide substitutions. Additionally, a total of five distinct genotype B3 sequences were reported from the States of Alaska, California, Florida, Kentucky, New York, Rhode Island, Texas, and Washington.
The source of this outbreak is unknown. Currently, there is no evidence of decreased vaccine effectiveness or changes in the virus that would result in increased severity.
The public health risk in the Region of the Americas for measles is considered high due to the persistence of the circulation of the virus from imported cases, which have resulted in a limited number of outbreaks, with several generations of cases and the appearance of cases associated with pre-existing outbreaks in new geographical areas.
Additionally, an increase in the susceptible population due to persistently low vaccination coverage related to factors such as the COVID-19 pandemic, increased vaccine hesitancy in some communities and sectors of the population, and limited access to health services, particularly for vulnerable populations.
Measles is only a car ride away! Measles is a highly contagious virus. Around 90% of people who are exposed to a person with measles will become infected if they are not vaccinated. Because measles is so contagious, it easily crosses borders. Currently, measles outbreaks are happening in parts of the United States and Canada, especially in Ontario, and around the world. With spring and summer travel season approaching, anyone who is not protected can get measles while traveling and can easily spread it to others when they return home. Large measles outbreaks are possible when measles cases reach at-risk populations with low immunization rates against measles. The best way to protect against measles is to make sure you are up-to-date on immunization with the measles-mumps-rubella (MMR) vaccine.
The best way to protect yourself and your loved ones is by getting the measles, mumps, and rubella (MMR) vaccine. You should plan to be fully vaccinated against measles at least 2 weeks before you depart. If your trip is less than 2 weeks away and you are not immunized, you should get a dose of MMR. The MMR vaccine protects against all 3 diseases.
CDC does not recommend measles vaccine for infants younger than 6 months of age. In addition, certain individuals cannot receive the MMR vaccine for medical reasons: people who have had an allergic reaction to a MMR vaccine, those with certain medical conditions, people who are immunocompromised, and people who are pregnant or planning to become pregnant soon.
Infants 6-11 months of age:
Children over 12 months of age:
Teens & adults with no evidence of immunity*:
*Acceptable evidence of immunity against measles includes at least one of the following:
Note: People who were vaccinated prior to 1968 with either inactivated (killed) measles vaccine or measles vaccine of unknown type should be revaccinated with at least one dose of live attenuated measles vaccine. This is important even when you are not travelling.
March 7, 2025, 2:00 PM ET | CDCHAN-00522
The Centers for Disease Control and Prevention (CDC) is issuing this Health Alert Network (HAN) Health Advisory to notify clinicians, public health officials, and potential travelers about a measles outbreak in Texas and New Mexico and offer guidance for prevention and monitoring. As of March 7, 2025, Texas and New Mexico have reported 208 confirmed cases associated with this outbreak (198 in Texas and 10 in New Mexico). As a part of this outbreak, two deaths have been reported: one in Texas and one in New Mexico. More cases are expected as this outbreak continues to expand rapidly.
With spring and summer travel season approaching in the United States, CDC emphasizes the important role that clinicians and public health officials play in preventing the spread of measles. They should be vigilant for cases of febrile rash illness that meet the measles case definition and share effective measles prevention strategies, including vaccination guidance for international travelers.
The risk for widespread measles in the United States remains low due to robust U.S. immunization and surveillance programs and outbreak response capacity supported by federal, state, tribal, local, and territorial health partners. Measles-mumps-rubella (MMR) vaccination remains the most important tool for preventing measles. To prevent measles infection and spread from imported cases, all U.S. residents should be up to date on their MMR vaccinations, especially before traveling internationally, regardless of the destination.
As of March 6, 2025, a total of 222 measles cases have been reported by twelve U.S. jurisdictions this year: Alaska, California, Florida, Georgia, Kentucky, New Jersey, New Mexico, New York City, Pennsylvania, Rhode Island, Texas, and Washington; 201 of which occurred in New Mexico and Texas. Most of the 222 cases are among children who had not received the MMR vaccine. There have been three outbreaks, with an outbreak defined as three or more related cases, reported in 2025, and 93% of cases are outbreak-associated. For comparison, 16 outbreaks were reported during 2024 and 69% of cases were outbreak-associated.
Talk to your doctor about the MMR vaccine, especially if you or your child plan to travel to an area with an ongoing outbreak or internationally. Two doses of MMR vaccine provide better protection (97%) against measles than one dose (93%).
