Measles returns to the United States: Why are eradicated diseases resurfacing?

The United States has seen measles cases within its territory increase by 180% so far this year compared to the previous year's total. A similar trend is occurring with whooping cough, which has doubled its incidence; and experts also warn of the threat of a possible return of other (or nearly) eradicated diseases such as rubella and polio.

The causes of this phenomenon are complex, but experts point to one key factor: the decline in vaccination rates among the population, a trend that could intensify following the arrival in government of figures with prominent anti-vaccine views.

Measles and whooping cough are on the rise in the United States.

The United States is currently experiencing a measles outbreak unprecedented in recent history. With its epicenter in West Texas, the disease has now spread to ten states (Indiana, Kansas, Michigan, Montana, Oklahoma, Ohio, Pennsylvania, New Mexico, Texas, and Tennessee), with more than 800 cases in total (600 of them in Texas alone) and three deaths, according to the Associated Press.

In addition, there are two more active outbreaks in North America : one in Ontario, Canada, with at least 1,020 reported cases, and another in Chihuahua, Mexico, with at least 514 cases. The WHO has linked the outbreak to the one in Texas.

At least in the United States and Mexico, the WHO explained late last month, the outbreak is spreading primarily in small, tightly knit communities where vaccination rates are low. A similar point is made by the Ontario Public Health Agency , which explains that the increase in the incidence of this disease is explained by "continued exposure and transmission among unimmunized individuals."

The pattern is similar in the case of whooping cough. According to NBC News , at least 8,064 cases have already been detected nationwide; in the same period last year, the figure was only 3,835, less than half that. Earlier this month, a study in the academic journal The BMJ warned that the United States is on track to record its highest incidence of this bacterial infection this year since 1948.

Again, in this case, experts point to the decline in vaccination rates, which they attribute directly to growing distrust of the virus . The Centers for Disease Control and Prevention itself admitted last year that the percentage of young children vaccinated against measles and whooping cough had dropped below 93%, down from 95% in 2019.

A warning of what can happen

Vaccine hesitancy is a growing problem globally, as the propaganda of certain anti-vaccine groups has taken hold. However, its impact is proving particularly devastating in the United States. There, the Trump administration has not only chosen an activist from these movements, Robert F. Kennedy Jr., as Secretary of Health and Human Services (i.e., the highest authority on public health matters); it is also cutting budget allocations for vaccination campaigns and is even discussing the possibility of completely eliminating vaccination against some infections.

The consequences of this shift could be terrifying . This Thursday, authors from Stanford, Baylor, Rice, and Texas A&M universities published a study in JAMA Network warning of the risk that several of these diseases could once again become endemic in the country, with the enormous cost in resources and lives that this would entail.

Specifically, these researchers performed mathematical simulations using large-scale epidemiological models that simulate the spread of infectious diseases in the United States based on different levels of childhood vaccination.

Thus, they concluded that, with current immunization levels, there is a high probability (83% of the simulations performed yielded this result) that measles endemicity will reestablish itself in the United States. In a scenario in which MMR vaccination coverage were reduced by 10%, the model estimated that 11.1 million measles cases would occur over the next 25 years; in contrast, a 5% increase in coverage would result in only 5,800 cases over the same period.

Other diseases will not necessarily become endemic again under current vaccination rates, according to the results of this experiment, but rubella, polio, and diphtheria could become so again if coverage continues to decline.

These predictions, however, do not take into account the possibility that immunizations could increase again in response to outbreaks and as a result of public health policies. Therefore, the authors emphasize the importance of these types of decisions moving in this direction, contrary to the course the current government seems determined to take.

Global consequences

Beyond the local consequences this infectious spread would have for the United States itself, the return of endemicity of these diseases in North American territory could have serious repercussions for the rest of the planet.

We must not forget, first of all, that these are highly contagious diseases that can spread through travel , as happened during the COVID-19 pandemic just five years ago. This wouldn't be the first time, either, that something like this has happened in the case of measles: in 2015, an outbreak of the infection occurred with its epicenter in Disneyland (California, United States) that, as the specialized journal Human Vaccines & Immunotherapeutics points out, crossed the borders of the United States and spread to Canada and Mexico.

This possibility is especially worrying for less developed regions , such as many Asian, Latin American, and African countries, where health systems are more fragile and vaccination coverage is lower among the population. Some of these areas, currently the last bastions of nearly eradicated diseases like polio, could become hotspots for a new spread of these diseases.

Along these lines, and even if they are capable of a more effective response, countries with the largest volume of travel to North America, such as the European Union or Japan, could also be severely affected by a potential endemicity in the United States.

Ultimately, we must view the current measles and whooping cough outbreaks in the United States as warnings of the devastating impact of vaccine misinformation. It's important to confront this pseudoscientific thinking for the problem it truly is; our best tools to combat it are aggressive and expansive health policies and accurate and rigorous information about the importance of vaccination to protect our health and that of others.

References

Kiang MV, Bubar KM, Maldonado Y, Hotez PJ, Lo NC. Modeling Reemergence of Vaccine-Eliminated Infectious Diseases Under Declining Vaccination in the US . JAMA (2025). DOI: 10.1001/jama.2025.6495

Devi Shastri. Tennessee joins nine other US states with minor outbreaks. Here's what to know. Associated Press (2025). Viewed online at https://apnews.com/article/measles-outbreak-texas-rfk-new-mexico-kansas-vaccine-e904ec9781f1d164c73afe4ab71774fe

WHO (2025). Disease Outbreak News - Measles - United States of America. Accessed online at https://www.who.int/emergencies/disease-outbreak-news/item/2025-DON561 on 25 April 2025.

Public Health Ontario (2025). Enhanced epidemiological summary - measles in Ontario. Accessed online at https://www.publichealthontario.ca/-/media/Documents/M/24/measles-ontario-epi-summary.pdf?rev=4a12b7e5656f446183ebc28c6a1c54c8&sc_lang=en&hash=F6B7451D53B1027FE47A0A142E4EEBA2 on April 25, 2025.

Owen Dyer. Whooping Cough: Cases soar in US. The BMJ (2025). DOI: https://doi.org/10.1136/bmj.r704 .

Ranee Seither, Oyindamola Bidemi Yusuf, Devon Draman et al. Coverage with Selected Vaccines and Exemption Rates Among Children in Kindergarten — United States, 2023–24 School Year. CDC - Morbidity & Mortality Weekly Report (MMWR). DOI: http://dx.doi.org/10.15585/mmwr.mm7341a3

Margaret K Doll, John W. Correira. Revisiting the 2014-15 Disneyland meals outbreak and its influence on pediatric vaccinations. Human Vaccines & Immunotherapeutics (2021). DOI: 10.1080/21645515.2021.1972707

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