The Americas are currently experiencing a significant measles resurgence, with over 2,500 confirmed cases across the United States, Canada, and Mexico. This outbreak represents an 11-fold increase compared to the same period in 2024, prompting the World Health Organization to categorize the region as having a “high” risk for measles outbreaks, compared to a “moderate” risk globally.
The Current Situation
In Canada
Canada is facing its most severe measles outbreak in over 25 years, with more than 1,000 cases reported in Ontario alone since mid-October 2024. As of April 12, 2025, Canada has reported 1,069 confirmed and probable cases across seven provinces: Alberta, British Columbia, Manitoba, Ontario, Prince Edward Island, Quebec, and Saskatchewan. This far exceeds the 177 cases reported in 2024 and represents the highest annual case count since Canada achieved measles elimination in 1998.
The majority of Canadian cases (83%) are linked to a multi-jurisdictional outbreak that began when an internationally imported case attended a large gathering in New Brunswick in October 2024. Most affected individuals are either unvaccinated (84%) or have unknown vaccination status (12%).
In the United States
The U.S. has documented 1,001 confirmed measles cases across 31 jurisdictions as of May 8, 2025. Texas has become the epicenter of the outbreak, accounting for 683 of these cases. The outbreak has also significantly affected New Mexico, Oklahoma, and Kansas.
There have been 14 outbreaks (defined as 3 or more related cases) reported in 2025, with 93% of confirmed cases being outbreak-associated. Tragically, three deaths have occurred-two unvaccinated children in Lubbock, Texas (ages six and eight), and one adult in New Mexico-marking the first measles deaths in the U.S. since 2015.
Understanding Measles
Measles is one of the most highly communicable diseases in the world. The virus spreads through respiratory droplets and can remain airborne for up to two hours after an infected person leaves an area.
Symptoms and Progression
Measles develops in stages over 2-3 weeks:
- Incubation period: 10-14 days after exposure with no symptoms
- Initial symptoms: Fever (potentially as high as 105°F/40.6°C), dry cough, runny nose, sore throat, and inflamed eyes
- Distinctive signs: Koplik’s spots (tiny white spots with bluish-white centers inside the mouth)3
- Rash development: A red, blotchy rash that begins on the face and spreads downward to the rest of the body
- Recovery: The rash typically lasts about seven days, with cough and skin peeling potentially continuing for about 10 days
A person with measles can spread the virus for approximately eight days-from four days before the rash appears until four days after the rash has been present.
Who’s at Risk?
The current outbreak data shows clear patterns of vulnerability:
- Age distribution: In the U.S., 30% of cases are in children under 5 years, 38% in those aged 5-19 years, and 31% in adults 20 years and older
- Vaccination status: 96% of U.S. cases are in unvaccinated individuals or those with unknown vaccination status
- Hospitalization rates: 13% of cases (126 of 1,001) have required hospitalization
Prevention and Protection
Vaccination Recommendations
The most effective protection against measles is vaccination. Current recommendations include:
- Children: Two doses of measles-containing vaccine (MMR or MMRV). The first dose at 12-15 months of age and the second dose at 18 months or later, but no later than school entry
- Adults born in or after 1970: At least one dose of MMR vaccine if not previously vaccinated or without evidence of immunity
- Adults born before 1970: Generally presumed to have natural immunity, but certain groups (healthcare workers, travelers, military personnel, and post-secondary students) should receive MMR vaccination
The efficacy of a single dose of measles vaccine given at 12 or 15 months is estimated at 85-95%, while two doses provide almost 100% protection.
Post-Exposure Prophylaxis
If you’ve been exposed to measles and are not immune, post-exposure prophylaxis (PEP) may be recommended:
- Measles-containing vaccine or human immunoglobulin may be used depending on your specific circumstances
- PEP should be offered to individuals not expected to have immunity to measles4
- Different strategies exist for various populations (immunocompromised individuals, infants, pregnant women)
What to Do If You Suspect Measles
If you or someone you know develops symptoms consistent with measles:
- Call your healthcare provider before visiting in person to avoid exposing others
- Stay home and isolate to prevent further transmission
- Follow public health guidance for testing and treatment
- If you’re in an outbreak area, be especially vigilant about monitoring for symptoms
The Path Forward
Public health authorities are implementing a multipronged approach to control the outbreaks:
- Enhancing surveillance and preparedness in high-traffic border areas
- Establishing service corridors and care pathways to reduce healthcare setting exposures
- Increasing vaccination coverage while targeting at-risk settings and populations
- Enhancing awareness and education among health professionals and the public
The current measles outbreaks serve as a stark reminder of the importance of maintaining high vaccination rates. With continued vigilance and appropriate public health measures, we can work toward containing these outbreaks and preventing future ones.
Remember: Vaccination remains our most powerful tool against measles, with routine immunization being the best strategy to mitigate outbreaks and reduce the need for post-exposure interventions
