America's measles comeback, explained

The United States is about to lose something it earned 26 years ago: its measles elimination status.

Not because measles disappeared from the planet. Because the country stopped being able to keep it out.

In the first two months of 2026, the US recorded 976 measles cases. All of 2025 saw 2,144 cases — the worst year since 1991. And now, public health experts are warning that a certification the country has held since 2000 is slipping away.

Here's what that means, why it's happening, and what comes next.

What is measles elimination status?

Elimination doesn't mean the virus is gone. It means the virus isn't spreading continuously inside your borders.

The Pan American Health Organization (PAHO) grants elimination status when a country proves it can interrupt measles transmission for at least 12 consecutive months. Cases still arrive from travelers. But they don't spark sustained outbreaks.

To keep that status, you need strong surveillance, high vaccination rates, and quick outbreak response.

The US earned it in 2000. The UK earned it in 2016, lost it in 2019, regained it in 2021 (mostly because COVID lockdowns reduced global transmission), and lost it again in 2026 after recording 2,911 cases in 2024.

Once you lose it, getting it back requires proving you've interrupted transmission for three years straight.

Why measles is different

Measles is one of the most contagious diseases on Earth.

Its basic reproduction number (R0) sits between 12 and 18. That means one infected person will typically infect 12 to 18 others in an unvaccinated population.

For comparison:

• COVID-19 (original strain): R0 of 2-3
• Ebola: R0 of 1.5-2.5
• Seasonal flu: R0 of 1-2

The virus can survive in the air or on surfaces for up to two hours. You can catch it by walking into a room 90 minutes after an infected person left.

That's why herd immunity requires 95% vaccination coverage. Anything less leaves enough gaps for the virus to spread.

The US national two-dose MMR vaccination rate is currently 92.7%. Close, but not close enough.

What actually happens when measles spreads

About one in four people infected with measles will be hospitalized. One to three out of every 1,000 will die.

The most common fatal complication is pneumonia, which accounts for 56-86% of measles deaths. Encephalitis (brain swelling) strikes about one in 1,000 cases, often causing permanent neurological damage.

Then there's subacute sclerosing panencephalitis (SSPE) — a rare but fatal brain disease that can develop 7-10 years after infection. Before measles was eliminated in the US, 7 to 11 people per 100,000 were at risk.

Young children and adults over 20 face the highest complication rates. But no age group is immune.

In 2024, measles caused an estimated 95,000 deaths globally — mostly among unvaccinated children under five.

How we got here

Measles never went away worldwide. It just stopped circulating in countries with strong vaccination programs.

Global cases have surged in recent years:

• 2024: 359,466 confirmed cases worldwide
• 2025: The Americas saw an 11-fold increase compared to 2024

In the US, vaccination rates have been slipping. The 2023-2024 school year saw MMR coverage at 92.7%, down from higher levels in previous decades. Some states and communities have rates well below the national average.

The result: 49 outbreaks in 2025, with 88% of cases linked to those outbreaks. Seven new outbreaks have already been reported in 2026.

International travel brings the virus in. Gaps in vaccination allow it to spread.

What happens if the US loses elimination status

Practically, not much changes overnight. The virus doesn't care about certifications.

But symbolically, it marks a shift: from a country that controlled measles to one where measles is circulating again.

It also affects global confidence. When wealthy countries with strong health infrastructure lose elimination status, it signals that vaccination rates are dropping and public health systems are under strain.

The UK has now lost its status twice. The first time, it took years of targeted vaccination campaigns to regain it — only to lose it again when coverage slipped.

The US could follow the same pattern. Regaining elimination status would require at least three years of proving the virus isn't spreading continuously. That means higher vaccination rates, better outbreak containment, and consistent public health investment.

The Samoa lesson

In 2019, Samoa's MMR vaccination rate dropped from 74% to around 31% after two tragic deaths linked to improperly prepared vaccines (mixed with expired muscle relaxant instead of water).

Within months, measles tore through the island nation. Over 5,700 cases. 83 deaths. An infection rate of more than 2.5% of the entire population.

Nearby Fiji and Tonga, which maintained high vaccination rates, saw outbreaks but no deaths.

The lesson: when vaccination rates fall below the threshold needed for herd immunity, measles spreads fast and kills children.

The bottom line

Measles elimination isn't permanent. It's something you maintain.

The US maintained it for 26 years by keeping vaccination rates high and responding quickly to imported cases. Now, with rates slipping and outbreaks spreading, that status is at risk.

The virus itself hasn't changed. What's changed is how many people are protected against it.

Getting elimination status back will be harder than losing it. And every gap in coverage is a place where measles can spread — and where children can die from a disease we know how to prevent.