Measles is a highly contagious respiratory virus that is spread through airborne droplets from the coughing and sneezing of an infected individual. Measles is caused by a single-stranded, enveloped RNA virus, with humans being the only natural hosts¹.

Recent cases and outbreaks in the United States have primarily been attributed to travelers who contract measles abroad, bring it into the country, and then spread it to communities with unvaccinated populations. To date in 2025, the US Centers for Disease Control and Prevention (CDC) reports that 96% of individuals with confirmed measles cases are either unvaccinated or have an unknown vaccination status².

The symptoms of measles generally appear 7 to 14 days after infection. Initial symptoms include fever, runny nose, cough, red eyes, and sore throat, followed by a rash that spreads all over the body. The rash usually begins as flat red spots on the face at the hairline and spread downward to the neck, trunk, arms, legs, and feet. Small, raised bumps may also appear on top of the flat red spots. When the rash appears, an ill person’s fever may spike to more than 104°F. After a few days, the fever subsides and the rash fades. An ill person is usually contagious from four days before to four days after the rash appears³.

Some individuals who contract measles may develop one or more complications such as diarrhea, ear infections, pneumonia, or encephalitis⁴. Complications are more common in children younger than five, adults over 20 years, and immunocompromised individuals. Unvaccinated pregnant women are also at risk of premature birth or having a baby with low birth weight⁵.

Measles is one of the most contagious diseases. According to the World Health Organization (WHO), one infectious person can infect 90% of unvaccinated individuals around them⁴. The virus spreads when an infected person breathes, coughs, or sneezes. It is highly contagious through droplet transmission and the virus can survive in the air and on surfaces for up to two hours^4,6.

The most effective way to control and prevent measles is through vaccination. The measles vaccine can be on its own or combined in the MMR vaccine (measles, mumps, rubella). Two doses of the vaccine are recommended.

En los países en los que los ciudadanos no están vacunados, el virus altamente contagioso se puede expandir rápidamente entre comunidades. In 2023, an estimated 10.3 million people contracted measles, and that number continues to rise⁷.

Additional steps to reduce infection risk include:

• Hand hygiene using soap and water or alcohol-based hand rubs if soap and water is not available,
• Through cleaning and disinfection of surfaces and high touch objects with products effective against the measles virus,
• Cough etiquette and social distancing,
• Stay home when sick and try to isolate

1. CDC | Clinical Overview of Measles
2. CDC | Measles Cases and Outbreaks – current as of May 8, 2025
3. CDC | About Measles
4. WHO | Measles
5. CDC | Measles Symptoms and Complications
6. CDC | How Measles Spreads
7. CDC | Global Measles Outbreaks