Deadly measles outbreak surges in US: CDC reveals highest case spike since 2019

Why is measles making a deadly comeback in the United States in 2025?

The United States is currently experiencing its worst measles outbreak in more than half a decade, according to new data released by the Centers for Disease Control and Prevention (CDC). As of April 10, 2025, the CDC has confirmed 712 measles cases spanning 24 states, the highest number reported since 2019, when 1,274 cases were recorded. If the trend continues, the country risks matching or exceeding the 2019 total, and potentially losing its measles elimination status—an achievement the US first secured in 2000.

The CDC reports that this dramatic rise in measles cases has largely stemmed from pockets of declining vaccination rates and persistent vaccine misinformation. These trends are fueling conditions for localized outbreaks, particularly in communities with lower immunisation coverage. Measles, a disease that was once nearly eradicated from the country due to widespread use of the MMR (measles, mumps, rubella) vaccine, is now resurging in ways that challenge public health agencies and local governments.

Which states are most affected by the current measles outbreak?

Measles cases have been confirmed in at least 24 US states, including California, Texas, New York, Florida, and Ohio. According to CDC surveillance, at least five of these states—Indiana, Kansas, New Mexico, Ohio, and Texas—are currently experiencing what it defines as “outbreaks,” meaning three or more related cases. Texas has emerged as the epicenter, with 541 cases reported to date, particularly concentrated in the western part of the state.

The outbreak in Texas began in January 2025 and continues to expand. The Texas Department of State Health Services has confirmed that most cases have occurred among unvaccinated children and teenagers, with the largest share in the 5-to-17 age group. As of the latest update, at least 56 people in Texas have been hospitalized due to complications from the disease. Tragically, two school-aged children who had not received the MMR vaccine have died. A third death, involving an unvaccinated adult in New Mexico, is currently under investigation.

How effective is the MMR vaccine, and what does the CDC recommend?

The CDC continues to underscore the effectiveness of the MMR vaccine as the most reliable form of protection against measles. One dose of the vaccine is about 93% effective, while two doses increase protection to 97%. The agency recommends the first dose be administered to children between 12 to 15 months of age, with a second dose given between ages 4 and 6.

Despite these recommendations, vaccination coverage has slipped in recent years. Among the confirmed cases in the current outbreak, approximately 97% are individuals who are either unvaccinated or whose vaccination status remains unknown. Only 1% of cases involve people who had received a single dose of the MMR vaccine, and just 2% were fully vaccinated with both doses.

Vaccinated adults typically do not need a booster, unless they fall into specific risk categories such as international travelers, healthcare workers, or individuals in areas experiencing active outbreaks. Nonetheless, the outbreak reveals a clear vulnerability among unvaccinated populations, especially in communities where vaccination hesitancy is common.

What is the risk of measles spreading further in the US?

According to health experts, the current pace of measles transmission raises serious concerns about the possibility of wider community spread, particularly in densely populated areas. Katherine Wells, public health director in Lubbock, Texas, which has reported over 30 cases, noted during a recent briefing that urban exposures—such as those occurring in grocery stores, shopping centers, or transit hubs—could significantly amplify the spread.

The contagiousness of measles is another critical factor. The virus is known to be among the most infectious pathogens, capable of lingering in the air for up to two hours after an infected person has left the area. One infected person can transmit the virus to 90% of non-immune individuals in close proximity, making outbreaks extremely difficult to contain without robust vaccination coverage.

According to the CDC, 11% of this year’s measles patients have required hospitalization, the majority of them under the age of 19. These complications can include pneumonia, encephalitis, and long-term neurological damage. Globally, measles remains a leading cause of vaccine-preventable death in children, despite the availability of a safe and effective vaccine.

How did the US eliminate measles, and what risks reversing that status?

Measles was declared eliminated in the United States in 2000, meaning there was no continuous disease transmission for more than 12 months within the country’s borders. This milestone was attributed to sustained, high vaccine coverage and a robust public health infrastructure capable of rapid case identification and contact tracing.

However, the CDC has warned that this status could be revoked if an outbreak within a region lasts longer than a year. The western Texas outbreak, already in its fourth month, has triggered concerns among federal health authorities that the country could be at risk of losing its elimination designation.

The situation echoes the 2019 measles resurgence, when outbreaks in New York’s Orthodox Jewish communities pushed the US dangerously close to losing its measles elimination status. That year’s outbreak prompted emergency declarations, mandatory vaccination orders, and school exclusions. Now, similar measures are being considered in parts of Texas and New Mexico.

What role do misinformation and policy gaps play in the outbreak?

Public health officials have repeatedly cited vaccine misinformation as a major factor behind declining immunisation rates. In many areas affected by current outbreaks, exemption rates for school-required vaccines have climbed in recent years, driven by philosophical or religious opposition, as well as disinformation campaigns around vaccine safety.

While the MMR vaccine has been rigorously studied and proven safe, social media has amplified unverified claims, including assertions that measles can be treated effectively with vitamin A or that natural immunity is preferable. Some of these claims have been circulated by public figures, including those who have previously campaigned against vaccine mandates.

The CDC has responded by ramping up its public education efforts and urging local health departments to target communities with low coverage for awareness campaigns. Nevertheless, enforcement remains inconsistent across states. Policies on non-medical vaccine exemptions vary widely, with some states allowing broad exemptions and others implementing strict mandates.

What are the implications for US public health going forward?

As the measles outbreak continues to expand, public health experts warn that the US may be entering a new phase in the battle against vaccine-preventable diseases. The COVID-19 pandemic disrupted routine immunisation schedules and led to a surge in vaccine skepticism, compounding existing gaps in MMR vaccine coverage. The current measles resurgence is being seen as a test of the country’s ability to rebuild trust in public health systems and maintain herd immunity.

Should the outbreak breach the 1,274-case mark set in 2019, it would become the worst measles surge in the US since 1992, when over 2,200 cases were reported. While the figures are still far below historic highs from the pre-vaccine era—when hundreds of thousands of cases occurred annually—they signal a concerning backslide.

Experts stress that the only viable path forward is through improved vaccination outreach, timely disease surveillance, and effective community engagement. Without high levels of vaccine uptake, diseases once thought eliminated may continue to return in preventable waves, placing the most vulnerable populations—especially children—at heightened risk.