Fact Sheet: Preventing the Spread of Measles

Measles is a highly contagious respiratory illness that can be prevented with vaccination. Medical complications from the measles can have serious health effects and cause death in vulnerable populations. 

Measles outbreaks are reported annually worldwide. In 2024, 285 measles cases were reported in 33 U.S. jurisdictions. As of April 10, 2025, the Centers for Disease Control and Prevention (CDC) reported 712 confirmed measles cases in the U.S. so far this year, with two confirmed deaths and one under investigation. Affected states include Alaska, Arkansas, California, Colorado, Florida, Georgia, Hawaii, Indiana, Kansas, Kentucky, Maryland, Michigan, Minnesota, New Jersey, New Mexico, New York City, New York State, Ohio, Oklahoma, Pennsylvania, Rhode Island, Tennessee, Texas, Vermont, and Washington.  

In response to measles outbreaks in Texas and New Mexico, the CDC issued a Health Alert Network Health Advisory on March 7, 2025, to notify clinicians, public health officials, and potential travelers about exposure risks and provide contagious disease prevention recommendations.  

Exposure Risk 

Outbreaks typically occur in places where people are not vaccinated, or their vaccination status is not known. According to the CDC, measles may be spread locally or by infected domestic and international travelers.  

Measles was declared eliminated in the U.S. in 2000 after almost 1,300 cases were reported in 31 states in 2019, the most confirmed cases since 1992. During the COVID-19 pandemic, over 61 million doses of measles vaccine were postponed or missed worldwide, increasing the likelihood of outbreaks.  

The virus is transmitted by direct or airborne contact with infectious droplets that spread when an infected person breathes, coughs, or sneezes. Measles virus can remain infectious in the air for up to two hours after an infected person leaves an area. Measles is infectious from four days before the rash appears through four days after rash onset. 

People with a high risk for severe illness and complications from measles include: 

• Infants and children under age 5 

• Adults over 20 years old 

• Pregnant women 

• Those with compromised immune systems 

Vaccination  

Vaccination is the primary way to prevent the spread of measles. A measles shot is administered as the combination measles-mumps-rubella (MMR) vaccine, or in a combination that includes varicella (MMRV). Single-antigen measles vaccine is not available in the U.S. 

All states and the District of Columbia require vaccinations for children entering kindergarten. All states allow medical exemptions to these requirements, and some states also offer exemptions for religious or philosophical reasons.  

Public health officials report that one dose of MMR vaccine is approximately 93 percent effective at preventing measles, while two doses are approximately 97 percent effective. People who do not respond to the measles component of the first dose of MMR vaccine typically respond to the second dose. After two doses, a booster vaccine is not needed later in life. 

The more people who are vaccinated, the greater the protection for everyone – regardless of their vaccination status. This is referred to as herd or group immunity. Because measles is highly contagious, a significant percentage of the population needs to be vaccinated against it to help close potential exposure gaps. 

Immunity 

People are presumed to be immune to measles if they have:  

• Written documentation of adequate vaccination, either one or more doses of a measles vaccine administered on or after the first birthday for preschool-age children and adults not at high risk, or two doses of vaccine for school-age children and adults at high risk, including college students, healthcare personnel, and international travelers 

• Laboratory evidence of immunity or confirmation of having had measles 

• Birth date before 1957 (measles exposure is presumed)  

Symptoms, Diagnosis, and Treatment 

Measles typically begins with a mild to moderate fever accompanied by cough, coryza (inflammation of mucous membranes in the nose), and conjunctivitis (pink eye). Diarrhea, nausea, and vomiting may also occur. Two to three days later, Koplik’s spots, a characteristic sign of measles, may appear. Fever may spike to 104°F or even higher. A red blotchy rash appears, usually first on the face, along the hairline and behind the ears. The rash rapidly spreads downward to the chest and back, then to the thighs and feet. In about one week the rash fades in the same sequence that it appeared. 

Laboratory tests of blood samples are used to verify a measles diagnosis. During an outbreak, medical providers are encouraged to consider measles in patients of any age who have a fever and rash.  

There is no specific antiviral therapy for measles. Supportive medical care helps relieve symptoms and addresses potential complications such as bacterial infections. In severe measles cases among children, vitamin A is usually administered because deficiency is a risk factor. 

Post-Exposure Recommendations 

The MMR vaccine, if administered within 72 hours of initial exposure, or immunoglobulin (IG), if administered within six days of exposure, may help prevent measles or lessen measles symptoms. These interventions are called post-exposure prophylaxis (PEP). Other recommended measures include: 

• Offering vaccination to non-immune individuals 

• Providing PEP to susceptible contacts 

• Practicing social distancing (isolation, quarantine, exclusion) 

• Encouraging monitoring and reporting of symptoms 

U.S. public health recommendations include the following: 

1. People without evidence of immunity and/or who have been exempted from measles vaccination, and who do not receive PEP within the recommended time period should be excluded from affected institutions in the outbreak area until 21 days after the onset of rash. 

2. People who receive PEP should be monitored for signs and symptoms consistent with measles for at least one incubation period. 

3. Infected people should be isolated for four days after they develop a rash. 

4. Airborne precautions should be followed in healthcare settings regardless of presumptive immunity status.  

Occupational Safety and Health Administration (OSHA) standards intended to help protect workers from exposure to measles include the Personal Protective Equipment standard (29 CFR 1910.132) and the Respiratory Protection standard (29 CFR 1910.134). Employment law attorneys advise employers to develop policies regarding notifications of potential exposure or a confirmed case of measles.   

Other Preventive Steps 

In addition to vaccination, it’s important to practice good hygiene: 

• Cover the mouth and nose with a tissue when coughing or sneezing, then throw the tissue away 

• Wash hands often with soap and water 

• Avoid sharing drinks or eating utensils 

• Disinfect frequently touched surfaces such as doorknobs, tables, and counters; standard household disinfectants kill the measles virus. 

Healthcare personnel: People who work in healthcare settings should have documented evidence of immunity against measles. 

International travelers: Refer to the CDC’s Travelers’ Health webpage for guidance on global travel precautions for children and adults. 

Women of childbearing age: Women are advised to get at least one dose of MMR vaccine before they get pregnant if they do not already have immunity. Studies show that measles is associated with miscarriage and premature birth.  

Suspected or known exposure to measles should be reported to a personal healthcare provider for follow-up. Contact WorkCare for guidance on infectious disease prevention and management in the workplace.