Southwest US Hit By Deadliest Measles Outbreak in a Generation

In late February, a school-aged child in Texas died from measles, marking the United States's first fatality from the virus in a decade. Less than 2 weeks later, a second suspected death—a deceased adult from New Mexico—was reported. 

An aerial photo of Seminole, Texas, currently at the heart of a massive measles outbreak. Source

These deaths are part of a massive measles outbreak that began in January 2025. In the just the last two months, the virus has spread like wildfire across the rural South Plains region of Texas and neighboring Lea County in New Mexico. Dozens of people have been hospitalized, and over 200 cases have been confirmed between the two states, though health officials warn that these numbers may represent a significant undercount. Infections are primarily concentrated in unvaccinated children, but the virus has infected multiple adults and several people who received at least one dose of measles vaccine. 

While the outbreak is still growing, it's already the region's worst epidemic in a generation and the biggest in the US since at least 2019. The surge in cases has come amid rising vaccine hesitancy in the United States, capped off by the appointment of Robert F. Kennedy Jr., a notorious vaccine skeptic, as US health secretary. 

With cases expected to rise further and vaccine supplies in the Southwest already stretched, people are asking questions. How contagious is measles? What kind of complications does it cause? Are vaccinated people safe? And perhaps most importantly, nearly 30 years after measles was declared eradicated in the United States, why is this outbreak happening in the first place?

An Ancient Enemy

Measles has been with humans for a long time. It began as the Rinderpest virus, a now eradicated scourge of cattle, spilling into humans as far back as the 6th century BCE. The virus evolved over the centuries to more efficiently infect people, aided by the emergence of increasingly large cities that could sustain its spread. 

While not as deadly as Ebola or HIV, measles currently holds the title of most contagious virus to infect humans. The average measles patient will spread the virus to 12-18 others in a population with no immunity or social distancing measures. Before vaccines and modern medicine, this extreme infectivity meant that the virus infected most people in early childhood, killing millions each year.

Causing fever, respiratory symptoms, and rash, measles is also associated with severe complications in a small subset of cases. 1 in 5 unvaccinated people are hospitalized, 1 in 20 children get pneumonia, and 1 in 1000 experience brain inflammation. The combined effects of respiratory and neurological complications can be fatal in up to 1 in 300 cases. Additionally, measles attacks the immune system, meaning many survivors experience profoundly reduced immunity to other diseases for years after infection, increasing all-cause deaths.

It wasn't until 1963 that the first measles vaccine was developed. In the early days of mass vaccination in the 1980s, nearly three million deaths still occurred each year. That number has since fallen to around 100,000, translating to 60 million lives saved from 2000 to 2023.

Vaccination

In any infectious disease outbreak, the average infected person must infect less than one other person for cases to slow. Since this value starts at 12-18 for measles, outbreaks only stop when 90-95% of a population is immune—at which point the virus has so few people left to infect that immune people shield the non-immune in a concept called "herd immunity."

Measles is difficult to stop and requires mass vaccination due to its high infectivity, far outstripping other diseases like Smallpox and Influenza. Source

Thankfully, two-dose measles vaccines are 97% effective against infection, and immunity to the virus barely wanes over a lifetime. Even a single dose is 93% effective. In rare cases where a vaccinated person is infected, they typically experience milder disease. As such, a two-dose vaccination is usually enough for personal safety. Assuming enough people are vaccinated for herd immunity, mass vaccination can control the virus nationally.

There are caveats: small outbreaks can occur in highly immune populations, while vaccination rates slightly short of herd immunity are sustainable if outbreaks are quickly detected and contained. If vaccination rates in a community fall substantially, however, even to a relatively high level of 80%, a single arriving traveler with the virus can quickly spark a rapid outbreak. The virus will spread exponentially and won't slow unless it infects most of the unvaccinated population, or aggressive interventions are put in place. 

Vaccine hesitancy

Thankfully, by 1998, such outbreaks were already a shrinking concern in most developed countries. Deaths were nearly zero in the US, and measles was on the brink of eradication in many countries. Then, a British physician named Andrew Wakefield published a paper in The Lancet, a reputable medical journal, that would have reverberations for generations. The paper alleged links between the widely-used MMR (measles, mumps, and rubella) vaccine and autism, sparking a global health scare. As scientists began to look into the issue, vaccination rates plummeted.

Before long, investigators alleged that Wakefield falsified data in his 1998 study. Reports from The Sunday Times and BMJ showed that he misrepresented patient histories (including some of the vaccinated children not even having autism), altered pathology results, and recruited subjects via anti-vaccine activists. Wakefield was even accused of planning to profit from the scare by selling diagnostic kits and alternative treatments, with potential annual earnings running into the tens of millions. His 1998 paper was formally retracted in 2010, and Wakefield was banned from medicine in his home country of Britain.

By then, however, the damage had already been done. Anti-vaccine sentiments rose, new theories emerged that soured public appetite for other vaccines, and Wakefield himself found a friend in Robert F. Kennedy Jr., the current US health secretary.

Andrew Wakefield (left) poses with US health secretary Robert F. Kennedy Jr. (Center) at an event for the anti-vaccine documentary Vaxxed II: The People's Truth (2019). Source

Though vaccine hesitancy had been on the rise for much of the early 21st century following Wakefield's scandal, it found new fuel in 2020 with the emergence of COVID-19. New vaccines were hurriedly developed as the world faced its worst pandemic in a century. Serious side effects from these vaccines were rare, and they mostly had high efficacy against severe disease and infection.

However, mutations in the virus significantly reduced this efficacy, damaging trust in vaccines' efficacy. This wasn't helped by lagging guidance from officials, who often failed to take into account the waning of vaccines. At the same time, rare but serious side effects like myocarditis (heart inflammation) occurred, amplified by how many people were being vaccinated so quickly compared to other vaccines. 

Anger only increased as governments widely instituted aggressive measures to encourage vaccination, such as workplace mandates, firings, and vaccine passports. These often applied to populations at lower risk for COVID and higher risk for vaccine side effects (mainly young men), raising questions about the cost-benefit analysis applied to the vaccination program.

These factors combined provide fertile conditions for anti-vaccine sentiments to take root. A lot of this involved understandable hesitancy about COVID-19 vaccines and the credibility of health officials, but concerns quickly spread to other vaccines, and full-blown anti-vaccine sentiments surged. Many people who had trusted vaccines before the pandemic suddenly found their belief in modern medicine shattered. Unfortunately, this phenomenon would have consequences extending far beyond the pandemic. This has included the measles vaccine, which increasingly fewer parents accept.

As of the 2023-24 school year, only a handful of states vaccinate more than 95% of kindergarteners for measles, creating a generation without herd immunity. This includes Texas, now the epicenter of America's deadliest measles outbreak in decades.

Measles vaccination rates among US kindergarteners for the 2023-24 school year. Source

The Current Outbreak

Given that 95% vaccination is generally required for herd immunity, it's unsurprising that the outbreak first erupted in Gaines County, Texas, where the vaccination rate is just 82%. In such a low-immunity environment, an average person infected with the measles virus would theoretically infect multiple others. Instead of increasing steadily, cases would experience exponential growth, multiplying every few weeks to rapidly engulf the county and nearby areas.

Gaines is highly religious and rural, full of vast stretches of empty land. It's also home to a large Mennonite community where religious exemptions from measles vaccination are high, and measles cases have erupted in church communities. Data collection is poor, and it doesn't help that Texas health officials don't appear to be doing outreach in the area.

Vaccination rates also lag in areas around the Mennonite community, so what started as an isolated outbreak quickly spread to the neighboring Texan counties of Dawson, Lubbock, and Lynn, as well as Lea County, New Mexico. As of March 7, there were confirmed cases in over 220 people. However, this number is likely a drastic undercount. In February, when there were still only 49 cases in the outbreak, it was already estimated that 200-300 suspected cases in West Texas had not been tested. 

The spread of measles in Texas and New Mexico. Source

Due to limited testing, it's impossible to know how many have truly been infected. However, we do know that two deaths are being investigated, 1-3 cases out of 1000 result in death, and deaths lag infections by weeks. This would imply that measles had already infected around a thousand people in Texas and New Mexico by mid-February. Given the speed at which the epidemic has grown, its likely that hundreds more have been infected since.

Hospitals in Texas are now facing an influx of seriously ill children, many refusing to eat or drink. Doctors report that several children have already been intubated due to the respiratory complications of measles, including one person under six months of age.

At a White House press conference, however, Health Secretary Kennedy contradicted these reports, claiming that the hospitalizations were mainly for quarantine purposes. He described the outbreak as "not unusual" and was quiet about using vaccines to contain the virus. As cases increased, Kennedy did walk back some of his positions, calling the outbreak a "top priority" and writing an op-ed that partially focused on promoting vaccination.

Robert F. Kennedy, the US health secretary facing scrutiny for his handling of the current measles crisis and views associated with vaccine skepticism. Source

Raising eyebrows, however, Kennedy's guidance has primarily emphasized the importance of vitamins and supplements, prompting Texan health officials and one of his advisors to jump in, clarifying that vaccines were still the primary solution. His agency's top spokesperson also resigned over the outbreak, and he has faced intense scrutiny over a perceived lack of action on the outbreak. Meanwhile, the CDC, which already has its hands complete with measles, bird flu, and widespread firings, is launching a study on vaccines and autism—not surprising given Kennedy's connections with Wakefield.

The current outbreak has had the positive effect of increasing measles vaccinations in Texas as panicked parents rush to protect their kids, though supply has struggled to meet demand. Reports have emerged of empty CVSs in Austin and Lubbock, with the CDC sending thousands of extra shots.

Thankfully, there are early signs of the outbreak peaking in epicenters like Gaines County, but the danger is not over yet. Health officials in both states are still scrambling to contain the epidemic and confirm new cases, especially as it expands to new areas. Emergency vaccination clinics have been set up, and local governments are advising parents to immunize their children. The CDC has also deployed epidemiologists to help coordinate response efforts.

The resurgence of measles in the United States is not just a failure of vaccine coverage but a sign of the broader health threats facing the nation. Confidence in vaccines and modern medicine, in general, are failing, old diseases from the past are re-emerging, and the country is no more prepared for new diseases like bird flu than it was for COVID-19.