Yes — North America is grappling with a serious measles outbreak. The World Health Organization (WHO) recently classified the region as at “high” risk for measles, a sharp contrast to the “moderate” risk at the global level. This designation stems from rising case numbers and growing vaccine hesitancy. The United States, Canada, and Mexico are now facing their worst measles outbreaks in decades, with over 2,500 confirmed cases and four reported deaths across the three countries.
As of May 2025, the U.S. has reported nearly 1,000 cases, with Texas accounting for 683 of them. Canada has recorded over 1,000 cases, mainly in Ontario, marking its most severe outbreak in 25 years. In Mexico, the state of Chihuahua reported 786 cases in 2025 alone, a massive increase from just seven cases the previous year.
Experts at the Centers for Disease Control and Prevention (CDC) continue to lead efforts to stop the virus, ramping up vaccination campaigns and public health messaging. Yet, the outbreak highlights how vulnerable communities become when immunization levels fall below protective thresholds.
What Is Measles and Why Does It Matter?
Measles is a highly contagious viral illness that typically begins with fever, cough, runny nose, and red eyes. A rash follows — starting on the face and spreading to the rest of the body. While many people recover within two to three weeks, complications can be severe. These include pneumonia, ear infections, diarrhea, and in rare cases, encephalitis (brain swelling), which can cause permanent brain damage or death.
In high-income countries, measles kills about 1 in every 5,000 people who get infected. But in lower-income areas, limited access to healthcare and vaccines often pushes the fatality rate as high as 1 in 100.
What Is Herd Immunity, and Why Is It So Critical?
Herd immunity munity protects entire communities by making it harder for contagious diseases to spread. When enough people become immune, either through vaccination or prior infection, even those who can’t receive vaccines — such as newborns or immunocompromised individuals — are protected.
To stop measles, which is extremely infectious, about 95% of the population needs immunity. The MMR (Measles, Mumps, Rubella) vaccine is 97% effective after two doses, making it the best defense against outbreaks.
Where Has Measles Spread in North America?
United States
As of May 1, 2025, the United States has confirmed 935 measles cases across 30 states — the largest outbreak in over 20 years. Texas is at the epicenter, particularly Gaines County, which alone reported 396 cases. Other affected states include New Mexico (67 cases), Kansas (37), and Oklahoma (16).
Tragically, three deaths have occurred: two unvaccinated children in Texas and one unvaccinated adult in New Mexico. Mennonite communities, where religious beliefs and limited healthcare access often lead to low vaccine uptake, cluster these cases. The Texas Department of State Health Services has issued statewide alerts and encouraged residents to check their vaccine records.
In neighboring New Mexico, officials linked the outbreak to the Texas cases. The majority of the state’s infections have emerged in Lea County, which borders Gaines County.
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Canada
Canada is battling its most significant outbreak in over 25 years, with more than 1,000 confirmed cases in Ontario alone since October 2024. Public Health Ontario traced the outbreak to a large religious gathering in New Brunswick involving Mennonite communities.
Most Canadian cases involve unvaccinated children and teenagers. Hospitals in Ontario have reported multiple intensive care admissions. The outbreak has also extended to Quebec and Alberta, putting Canada’s measles elimination status at risk.
Mexico
In Chihuahua, Mexico has documented 786 measles cases in 2025, compared to just seven nationwide the previous year. A 31-year-old unvaccinated man from Ascension, Chihuahua, died in early April.
The outbreak is tied to cross-border travel with Texas and is heavily concentrated in Mennonite communities that frequently travel between Mexico and the U.S. The Mexican Ministry of Health has issued a travel advisory for Canada and the U.S. and launched a National Vaccination Week to boost immunization rates, especially in rural areas.
Why Is Measles Spreading Again?
The key reason for the resurgence: declining vaccination rates. Measles is so contagious that one infected person can spread it to 90% of unvaccinated people nearby. To avoid outbreaks, 95% of the population needs to be immunized with two doses of the MMR vaccine.
In the U.S., CDC data shows that 3.3% of kindergartners had exemptions from at least one vaccine in the 2023–2024 school year — up from 3% the year before. In some states, like Idaho, Alaska, and Arizona, exemption rates are above 7%. These clusters of unvaccinated individuals form hotspots for outbreaks.
Canada has also seen provincial dips in immunization, and in Mexico, rural access challenges persist. Globally, the WHO reports that measles cases have increased by 30% over the past year, largely due to misinformation and vaccine hesitancy.
Who Are the Anti-Vaxxers and What Do They Believe?
Anti-vaccine groups — often labeled “anti-vaxxers” — cite fears of side effects, government mistrust, or religious beliefs as reasons for opposing vaccines. In Ontario and Chihuahua, Mennonite communities have historically opted out of immunization, which has fueled the spread of measles in 2025.
One persistent myth is the false claim that vaccines cause autism, which originated from a debunked 1998 study. Despite overwhelming scientific evidence disproving any link, the myth continues to circulate online and undermine public confidence.
How Well Does the Measles Vaccine Work?
The MMR vaccine is one of the most effective vaccines ever created. Two doses offer 97% protection; one dose provides about 93%. Health officials recommend children get the first dose between 12–15 months of age and the second between 4–6 years.
From 2000 to 2020, WHO estimates suggest the MMR vaccine prevented over 31.7 million deaths. In countries with high vaccine coverage, measles was nearly eliminated. However, lower vaccination rates have allowed it to make a dangerous comeback.
Breakthrough infections in vaccinated people do occur but are rare and far less severe. Fully immunized individuals usually avoid the most serious complications.
The MMR vaccine also remains extremely safe. Numerous studies from the CDC and Institute of Medicine have proven that it does not cause autism or other chronic health issues.
What Role Does U.S. Health Secretary Robert F. Kennedy Jr. Play?
The appointment of Robert F. Kennedy Jr. as U.S. Health and Human Services Secretary under President Donald Trump has sparked outrage among scientists and health officials. Kennedy, a longtime vaccine skeptic, has promoted widely debunked theories, including that the MMR vaccine contains aborted fetal tissue and causes autism.
Public health authorities have repeatedly refuted these claims. While the rubella component of the vaccine was developed using a fetal cell line from the 1960s, the final vaccine does not contain any fetal tissue.
Kennedy has also downplayed the measles outbreak, proposing unproven alternatives like vitamin A supplements and cod liver oil — despite scientific consensus showing these do not prevent infection.
His leadership has fueled distrust in official health messaging, making it even harder to combat the measles resurgence across North America.
