The United States and Canada have experienced one of their worst measles epidemics for years, while the virus has also crossed in neighboring Mexico.
A total of 2,500 cases and four deaths were reported in epidemics in the three countries. The hesitation in the vaccine was blamed.
Here is what we know of epidemics so far and why cases of measles are increasing.
What is measles?
Measles is a very contagious viral disease that begins with symptoms, especially high fever, cough, flowing nose, red or aqueous eyes and light sensitivity. A few days after the infection, a red and stained rash rash generally appears on the face and spreads in the body. Fatigue and loss of appetite are also common.
Most people are recovered in two to three weeks, but complications, especially in young children and those whose weakened immune system, can be serious.
These include infections of the ear, diarrhea, pneumonia and swelling of the brain (encephalitis) which can cause permanent disability or death. In richer countries, measles causes approximately a death in all 5,000 cases, but in low -income regions with lower health systems, the mortality rate can be as high as in 100.
Before the introduction of the measles vaccine in 1963, approximately 3 to 4 million cases of measles were reported each year in the United States, with hundreds of deaths and thousands of hospitalizations. In 2000, after a generalized vaccination, measles was declared “eliminated” in the United States – which means that there had been no continuous transmission of the disease for more than 12 months. Countries that have eliminated a disease through vaccines are considered to have “immunity from the herd” as long as vaccines continue to be offered to everyone.
What is the immunity of the herd?
The immunity of the herd occurs when enough people in a community become sheltered from a disease, either by vaccination or by recovering from an infection.
The number of people who must be immunized in order to reach the immunity of the herd for the whole community varies from one illness to another. Measles, which propagates very easily, requires that 95% of a community have immunity.
When most people are sheltered, the disease has much more difficult to spread – which means that it is more likely to die before they can be transmitted to another host. This helps protect those who cannot be vaccinated for specific reasons, including newborns or people with certain health problems.
Experts say that the safest way to maintain the immunity of the herd is by vaccination due to the potentially serious effects of infection of measles.
What is the effectiveness of the measles vaccine?
According to the World Health Organization (WHO), vaccination against measles prevented around 31.7 million deaths worldwide between 2000 and 2020.
The measles vaccine, mumps and rubella (MMR), widely used worldwide, offers a protection of approximately 97% against measles virus, according to public health agencies.
The vaccine is normally given to children in two stages: the first dose at 12 months and the second at around three years and four months (when the child is approaching preschool), as part of routine immunization programs in countries like the United Kingdom.
Percée cases in vaccinated people are rare and generally mild.
Where is the measles spread to North America?
North America is experiencing significant resurgence of measles, with more than 2,500 confirmed cases in the United States, Canada and Mexico. Three deaths took place in the United States and one in Mexico. The epidemic began at the end of 2024 in Ontario, Canada, before spreading to Texas and northern Mexico at the beginning of 2025, with Mennonite communities (anabaptist Christian congregations), a historically undervacinated population, being the most difficult.
An WHO report in April said that cases of measles in the Americas in the first three months of this year were 11 times higher than during the same period in 2024. The region is now faced with a “high” risk of blast flambes, compared to a “moderate” risk worldwide, said the officer.
UNITED STATES
The United States has so far reported 935 cases of confirmed measles in 30 states, Texas being the epicenter of the epidemic, representing 683 of these cases. The epidemic has also spread to New Mexico (67 cases), Oklahoma (16) and Kansas (37).
Three people died of measles between February and April, including two unvaccinated children in Texas and an adult not vaccinated in New Mexico. These have mark the first deaths of the country’s measles since 2015.
In 2019, the United States has experienced its largest measles epidemic since 1992, with 1,274 confirmed cases reported in 31 states, but no deaths.
Canada
Meanwhile, Canada knows its worst measles epidemic in more than 25 years. Since mid-October 2024, Ontario has recorded more than 1,000 cases alone.
Canadian officials have confirmed that the epidemic came from a large rally in the New Brunswick province, which involved Mennonite communities, which aim for a simple life and tend to avoid modern technology and medicine.
Mexico
In Mexico, the number of measles cases has increased sharply this year in the northern state of Chihuahua, where 786 cases have been reported so far. Only seven cases were reported throughout the country last year. A 31 -year -old non -vaccinated man, Chihuahua, died of the disease in early April.
Why is measles spread?
According to WHO and US Centers for Disease Control and Prevention (CDC), the main reason why measles is that fewer people take vaccines. Disinformation and growing hesitation have seen the vaccination rates fall below the level necessary for the immunity of the herd.
In some Canadian American and province states, exemptions – give non -medical reasons for the drop in vaccines, as for personal or religious reasons – become more common. This has led to the existence of clusters of non -vaccinated people who are more vulnerable to epidemics when exposed to the virus.
The American CDC said that during the 2023-2024 school year, exemptions from one or more vaccines were claimed by parents or caregivers of 3.3% of preschool children, against 3% the previous year. Exemptions were higher in 40 states and in the Columbia district, with 14 states reporting exemption rates above 5%.
Health officials point out how closely connected to the United States, Canada and Mexico communities with people who travel between them. Mennonite groups, in particular, have solid cross -border links and lower vaccination rates, which facilitates the spread from one region to the other.
Who are the “anti-Vaxxers” and what are their concerns?
Anti-Vaccin defenders, often called “anti-vacuum”, oppose vaccinations for a certain number of reasons, including fears concerning side effects, distrust of pharmaceutical societies or government agencies and religious or personal convictions.
Mennonite groups of Ontario and Chihuahua have also historically hesitated to take vaccines, and health authorities claim that a significant share of recent cases of measles in these areas is concentrated in this population.
One of the most persistent myths stimulating the hesitation of vaccines is the assertion that vaccines cause autism. This belief follows from a 1998 study which has since been discredited and retracted.
The choice of RFK JR of Trump as a health secretary will still push the levels of vaccination further?
The appointment of Robert F Kennedy Jr, as an American secretary for health and social services, has aroused concerns among health experts, especially since cases of measles are up across North America.
Kennedy, a long -standing skeptic of the vaccine, has repeated false claims that vaccines are linked to autism and that the ROR vaccine contains “aborted fetus debris”.
Health experts have demystified this complaint. The rubella part of the vaccine was manufactured using laboratory cultivated cells which were copied from a single fetal sample taken in the 1960s. These cells have multiplied in laboratories for decades and are used to develop the virus necessary for the vaccine. But the cells themselves are eliminated during the process, so there is no fetal tissue in the real shooting.
Kennedy was criticized for having minimized the severity of the current measles epidemic and to promote unproven treatments for measles. He suggested alternatives, including vitamin A supplements and cod liver oil, which, according to experts, does not replace vaccination and are not supported by strong scientific evidence.
Kennedy has also made major changes to the Ministry of Health and Social Services, dismissed thousands of employees and reducing budgets for key agencies such as CDC, which, according to experts, could weaken the country’s ability to respond to health emergencies.
