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As of April 15, 2025, measles continues to spread across the nation and does not appear to be slowing down, . In addition to outbreaks in the U.S., international public health organizations are reporting rises in cases across the globe. has confirmed cases in Argentina, Canada, and Mexico. The highly contagious nature of the virus coupled with outbreaks in multiple countries raises concerns about measles spreading globally and becoming more difficult to contain.Ìý

In an updated interview, George Mason Â鶹¹ú²ú epidemiologist and infectious disease expert answers questions about the evolving measles situation. She outlines how the United States is at risk of losing its status as a country that had eliminated the measles virus. Read the interview with Roess, . Roess shares concerns about the strain outbreaks could have on global public health systems and warns of the danger of the virus mutating [developing in a manner that results in changes from the original strain].Ìý

What is unique about the current measles outbreak? Ìý

This outbreak emerged in a somewhat rural part of the U.S. and then quickly spread to neighboring states, then Mexico and to other countries. This is happening just as the U.S. is reshaping how we approach prevention, detection, and response to new and emerging diseases, and scaling back our infectious disease research and surveillance infrastructure. In addition, the U.S. health system is already strained following a large tuberculosis outbreak in Kansas, bird flu (H5N1) across the country, and the highest number of flu cases we've seen in 15 years. Health care providers and public health workers are reporting that their facilities are understaffed and that they are exhausted. ÌýÌýÌý

Does this affect the U.S. and Mexico’s efforts to maintain elimination status?Ìý

ÌýIn 2000, measles was declared eliminated in the U.S. and it was considered unthinkable that we would see a measles outbreak of this magnitude here, in one of the wealthiest countries in the world. In 2016, measles was declared eliminated in the Western Hemisphere (from North to South America). This was largely due to countries combining efforts to improve vaccination and surveillance. It was an incredible multi-national accomplishment by governments and health care professionals. We are at risk of reversing that progress to eliminate measles from our hemisphere, because the presence of the virus in one region places the others at risk of it spreading there as well.Ìý

Why is it important to stop the spread now?Ìý

Preventable deathsÌý

Hospitalizations and deaths from measles are preventable. There is no reason that in 2025 we should accept that measles is making a comeback in the U.S. We have a vaccine that has been shown to be effective in preventing measles infection and has been shown over and over again to be safe. The good news is that most people in the U.S. are already vaccinated, and most parents want to vaccinate their kids. There are small groups of individuals who oppose vaccination and they are fueling this outbreak, which is sickening and killing mainly unvaccinated individuals.ÌýÌý

Immunocompromised individualsÌýÌý

One of the things we worry about is that there are a lot of immunocompromised individuals who are at risk of severe illness if they get measles. Think about how many people you know who are on immunosuppressive medications, who have heart disease, diabetes, or cancer. It represents a growing percentage of the U.S. population.ÌýÌý

Possible strain mutationsÌý

We also have to consider what this growing outbreak means for the risk of mutations arising that can lead to an even more infectious virus. So far, no concerning mutations have been found. For decades, measles has been a relatively stable virus, soÌýthe same vaccine has been in use and has been very safe and effective. If measles is allowed to spread unchecked, we could be in serious trouble of risking the virus mutating, leading to the vaccine becoming less effective in protecting against the virus. Why risk it?ÌýÌý

What can we expect now that the virus has crossed international borders?Ìý

We should expect to see more cases. Measles vaccination coverage is lower in Mexico than in the United States. That means that the virus will likely spread faster in Mexico unless a robust response is put into place immediately to stop transmission and improve vaccination. In addition, like in the U.S., there is a growing number of immunocompromised individuals in Mexico. A large-scale measles outbreak in Mexico can result in hundreds of severe cases that will be difficult to treat. If the outbreak grows, their health system will be under tremendous strain, which will mean a potentially higher death rate than what we have seen in the U.S.ÌýÌýÌý

Since the beginning of the current U.S. outbreak that started in 2024, we have seen how difficult it has been for clinics and hospitals to prevent and slow the spread of measles. I have the same concerns for Mexico. In the U.S., many of us are immunocompromised or are using medications that can weaken the immune system, which is partly why we have seen more than 10 percent of measles patients become hospitalized. Mexico also has a large number of immunocompromised individuals. If the outbreak grows, they will have to consider setting up separate measles units, because you don't want a highly infectious pathogen like measles in your hospitals where there are immunocompromised patients, especially if you have limited resources.Ìý

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MEDIA INQUIRIES: For reporters who wish to speak to Amira Roess about measles or other emerging diseases, please email media contact Michelle Thompson at mthomp7@gmu.edu.ÌýÌýÌý

Amira Roess is a professor of global health and epidemiology at George Mason Â鶹¹ú²ú's College of Public Health, Department of Global and Community Health. She is an epidemiologist with expertise in infectious diseases epidemiology, multidisciplinary and multi-species field research and evaluating interventions to reduce the transmission and impact of infectious diseases. Roess currently oversees several longitudinal studies to understand emergence and transmission of zoonotic infectious diseases globally, including the emergence and transmission of Campylobacter (with support from The Bill and Melinda Gates Foundation), MERS-CoV (with support from the U.S. National Science Foundation), and the development of the microbiome during the first year of life. She studies links between food animal production and emerging infectious and zoonotic diseases emergence globally, and mHealth (especially apps) technology integration and evaluations to reduce the impact of infectious disease outbreaks, promote health care, and help reduce disparities.Ìý

About George Mason Â鶹¹ú²úÌýÌýÌýÌýÌýÌý

George Mason Â鶹¹ú²ú is Virginia’s largest public research university. Located near Washington, D.C., Mason enrolls more than 40,000 students from 130 countries and all 50 states. Mason has grown rapidly over the past half-century and is recognized for its innovation and entrepreneurship, remarkable diversity, and commitment to accessibility. In 2023, the university launched Mason Now: Power the Possible, a one-billion-dollar comprehensive campaign to support student success, research, innovation, community, and stewardship. Learn more at .ÌýÌýÌýÌýÌý

About College of Public Health at George Mason Â鶹¹ú²úÌýÌýÌýÌýÌý

The College of Public Health at George Mason Â鶹¹ú²ú is the first College of Public Health in Virginia and a national leader in inclusive, interprofessional, public health research, education, and practice. The college is comprised of public health disciplines, health administration and policy, informatics, nursing, nutrition, and social work. The college offers a distinct array of degrees to support research and training of professionals dedicated to ensuring health and well-being for all. The college’s transdisciplinary research seeks to understand the many factors that influence the public’s health and well-being throughout the lifespan.ÌýÌý