Why the 2026 Measles Outbreak Is Different From Previous Years

The United States has dealt with measles outbreaks before. In 2019, over 1,200 cases were reported in what was then the worst year since 1992. In 2024, cases ticked up again with nearly 300 confirmed infections. But the 2026 outbreak is unfolding differently in several important ways, and understanding those differences is key to understanding the public health response and what it means for you.

The Scale Is Unprecedented in the Modern Era

As of mid-February 2026, more than 700 confirmed measles cases have been reported across 20 states. To put that in perspective, the U.S. typically sees fewer than 50 cases in an entire year during non-outbreak periods. We have already far surpassed that number in just the first six weeks of 2026, and the trajectory suggests the final count will be significantly higher.

The 2019 outbreak, which alarmed public health officials at the time, took a full 12 months to accumulate 1,282 cases. The current outbreak is on pace to exceed that total in a fraction of the time. Track the latest numbers on our outbreak map.

Geographic Concentration With Rapid Spread

One defining feature of the 2026 outbreak is the extreme concentration of cases in certain areas, combined with rapid geographic expansion. South Carolina accounts for more than 540 of the total cases, with the majority centered in specific communities with lower vaccination rates.

But unlike some previous outbreaks that remained relatively contained to a single community or region, this one has seeded cases across 20 states. The combination of a concentrated epicenter and widespread secondary transmission is a pattern that makes containment significantly more challenging.

The Vaccination Gap Has Widened

Perhaps the most consequential difference between 2026 and previous outbreak years is the size of the unvaccinated population. National MMR vaccination rates for kindergartners have declined from approximately 95% in the 2019-2020 school year to around 93% in recent years. While a two-percentage-point decline may seem small, it represents hundreds of thousands of additional unvaccinated children nationally.

More critically, the decline is not evenly distributed. Certain communities, schools, and counties have vaccination rates well below the threshold needed for herd immunity (generally considered to be 93-95% for measles). These pockets of low vaccination create vulnerability zones where the virus can spread rapidly once introduced.

Several factors have contributed to the widening gap:

• Pandemic disruption: Routine childhood vaccination rates dropped during the COVID-19 pandemic as families delayed or missed well-child visits. Not all of those missed doses have been caught up.
• Increasing vaccine hesitancy: Surveys show that confidence in childhood vaccines has declined in recent years, influenced by misinformation on social media and shifting public attitudes.
• Exemption trends: Non-medical exemptions from school vaccination requirements have increased in several states, allowing more children to enter school without full vaccination.

The Information Environment Has Changed

Previous measles outbreaks occurred in a different media landscape. In 2019, social media platforms were just beginning to grapple with vaccine misinformation. By 2026, the information ecosystem has become more fragmented, with anti-vaccine content reaching wider audiences through short-form video platforms, messaging apps, and algorithmically driven content feeds.

Public health officials have noted that countering misinformation is now a more significant part of outbreak response than in previous years. Inaccurate claims about vaccine safety, the severity of measles, and the effectiveness of alternative treatments circulate rapidly and can influence vaccination decisions in real time during an active outbreak.

This is one reason why reliable, fact-based resources matter more than ever. Our measles FAQ is built entirely on CDC guidance and peer-reviewed medical evidence.

Changes in Public Health Infrastructure

The public health infrastructure responding to this outbreak is also different from previous years. State and local health departments have experienced significant staffing changes and budget shifts following the COVID-19 pandemic. Some departments have fewer epidemiologists and disease investigators than they did in 2019, while others have restructured their operations in ways that affect outbreak response capacity.

At the federal level, the CDC's role in outbreak coordination continues to evolve. The agency provides technical guidance, laboratory support, and epidemiologic analysis, but the primary response responsibility falls to state and local authorities, whose capacity varies widely.

What Makes Measles Uniquely Challenging

It is worth remembering why measles outbreaks are so difficult to contain once they begin. Measles is among the most contagious infectious diseases known to science:

• The virus is airborne and can remain infectious in a room for up to two hours after an infected person has left.
• Each infected person typically transmits the virus to 12 to 18 other susceptible individuals (the R0 value), compared to 2 to 3 for influenza.
• Infected individuals are contagious for about four days before the characteristic rash appears, meaning they can spread the virus before they know they are sick.

These characteristics mean that even small gaps in vaccination coverage can lead to explosive outbreaks once the virus is introduced into a community.

What Public Health Experts Are Watching

Several indicators will determine how the 2026 outbreak unfolds over the coming weeks and months:

• Case trajectory: Whether the rate of new cases is accelerating, plateauing, or declining in affected areas.
• Geographic spread: Whether new states and communities report cases, or whether transmission remains concentrated in existing hotspots.
• Vaccination response: Whether outbreak-driven demand for MMR vaccine leads to meaningful increases in vaccination rates in affected communities.
• Complications: The rate of measles-related hospitalizations, pneumonia, encephalitis, and other serious complications.

The bottom line: The 2026 outbreak is a consequence of gradually declining vaccination rates meeting one of the most contagious viruses in existence. The solution remains the same as it has always been: the MMR vaccine is safe, effective, and widely available.

What You Can Do

Whether this outbreak continues to grow or begins to subside, the actions available to individuals remain straightforward:

1. Verify your vaccination status and your children's vaccination status. Two doses of MMR provide 97% protection.
2. Get vaccinated if you are behind on doses. Use our vaccine finder to locate a clinic near you.
3. Stay informed through reliable sources. Our outbreak map tracks confirmed cases by state.
4. Talk to your doctor if you have specific health conditions that affect your vaccination options.

The 2026 measles outbreak is different from previous years in scale, speed, and context. But the fundamental truth has not changed: measles is preventable, and vaccination is the most effective tool we have.