Measles.

A highly contagious viral infection caused by the measles virus, the disease threat primarily affects a person’s respiratory system. Transmitted through respiratory droplets when an infected person coughs or sneezes, measles was declared eliminated from the United States in 2000 — meaning that the country did not see continuous spread of the virus for a year or longer.  

“Typically, we will see isolated cases imported due to travel,” says Bryant’s School of Health and Behavioral Sciences Director Kirsten Hokeness, Ph.D. “Currently, we are seeing multiple outbreaks that are defined as three or more related cases across several states. There's been one confirmed death from the measles — the first since 2015 — and a second under investigation. As of March 6, 2025, there were 222 cases across 12 states.”

Below, Hokeness discusses the viral infection’s comeback, its level of contagiousness, and what the outbreak could look like in coming months:

What factors have contributed to the increase in measles cases despite the availability of vaccines?

MMR vaccine series completion rates among kindergarteners have been decreasing steadily over the past few years while the number of vaccine exemptions has been increasing. Parents can apply for an exemption for a variety of reasons — such as a religious or personal belief that goes against getting immunized. Ninety-five percent of people must be vaccinated for the community to be protected. Many areas are seeing high levels but there are pockets, like in Texas, where the rates are below 50 percent. In addition to vaccine rates decreasing, travel is increasing, which facilitates the spread of the virus; viral infections such as this have no geographic boundaries.

What makes the measles virus so contagious? Is it more contagious than other disease threats we see, like the flu or COVID-19?

Measles is one of the world's most contagious diseases, far more so than the flu or COVID-19. One reason for this is because of the route of transmission. The measles virus is spread via droplets, which can remain suspended for some time in the air and can persist on surfaces for hours after contamination. The virus has a long incubation period, and you can effectively spread measles to others before you develop any symptoms — aiding in the spread since people don’t know they are sick yet. The R0 (or average number of people who contract the virus from one person) is between 12 and 18. To add perspective, the R0 for flu is 1-2 — meaning one infected person is likely to infect one to two additional people.

What symptoms and complications are associated with measles?

Measles symptoms usually include a fever, characteristic rash, cough, and red eyes. Significant complications can occur in vulnerable populations such as children under the age of five, pregnant women, and people with compromised immune systems; this can include hearing loss, brain swelling, pneumonia, and death.  

What are the most effective strategies for identifying and managing measles outbreaks in communities?

Of the cases reported in 2025, 95 percent of them were seen in people who were unvaccinated or with unknown vaccination status, and 20 percent of those cases resulted in hospitalizations. Therefore, vaccination remains to be a proven and effective means to block transmission. Restoring confidence in the effectiveness of the MMR vaccine is paramount to managing the current and future measles outbreaks. It is important to note that there is no therapeutic intervention available for measles, thus prevention remains key. In addition, being vigilant about any signs and symptoms and seeing a healthcare provider right away is important to limit spread.  

How do you foresee the current outbreak evolving in the coming months?

Due to the highly transmissible nature of the virus, and as spring travel increases with school vacations, I expect case numbers to continue to increase. Hopefully, increased vaccination efforts, such as the delivery of doses to Texas, can help collapse pockets where large numbers of children remain unvaccinated. It does take time for immunity to build up, so things won’t turn around right away.  

Looking ahead, what steps could communities take to ensure measles is once again eliminated as a public health threat?

Public health is a collective responsibility aimed at protecting individuals, especially the most vulnerable, by ensuring the dissemination of accurate information about vaccine safety and efficacy to prevent outbreaks of measles and other vaccine-preventable diseases. We must work collectively to restore confidence in public health systems to stay healthy as a population.