Red Book Online Outbreaks: Measles

Measles Cases in 2025

As of April 10, 2025, a total of 712 confirmed measles cases were reported by 25 jurisdictions: 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.

There have been 7 outbreaks (defined as 3 or more related cases) reported in 2025, and 93% of confirmed cases (660 of 712) are outbreak-associated. For comparison, 16 outbreaks were reported during 2024 and 69% of cases (198 of 285) were outbreak-associated.

Age of 712 Cases
Under 5 years: 225 (32%)
5-19 years: 274 (38%)
20+ years: 198 (28%)
Age unknown: 15 (2%)

Vaccination Status of 712 Cases
Unvaccinated or Unknown: 97%
One MMR Dose: 1%
Two MMR Doses: 2%

Hospitalization of 712 Cases
11% of cases hospitalized (79 of 712)

Hospitalization by Age of 712 Cases
Under 5 years: 20% (45 of 225)
5-19 years: 7% (20 of 274)
20+ years: 6% (12 of 198)
Age unknown: 13% (2 of 15)

US Deaths in 2025
There have been 2 confirmed death from measles and 1 death under investigation.

Measles Cases in 2024
As of December 31, 2024, a total of 285 measles cases were reported by 33 jurisdictions: Arizona, California, District of Columbia, Florida, Georgia, Idaho, Illinois, Indiana, Louisiana, Maryland, Massachusetts, Michigan, Minnesota, Missouri, New Hampshire, New Jersey, New Mexico, New York City, New York State, North Carolina, Ohio, Oklahoma, Oregon, Pennsylvania, South Carolina, South Dakota, Tennessee, Texas, Vermont, Virginia, Washington, West Virginia, and Wisconsin.

There have been 16 outbreaks (defined as 3 or more related cases) reported in 2024, and 69% of cases (198 of 285) are outbreak-associated. For comparison, 4 outbreaks were reported during 2023 and 49% of cases (29 of 59) were outbreak-associated.

Vaccination Status of 285 Cases:
Unvaccinated or Unknown: 89%
One MMR Dose: 7%
Two MMR Doses: 4%

Age of 285 Cases:
Under 5 years: 120 cases (42%)
5-19 years: 88 cases (31%) 
20+ years: 77 cases (27%)

Hospitalization by Age of 285 Cases:
40% of cases hospitalized (114 of 285 cases) for isolation or management of measles complications.
Under 5 years: 52% (62 of 120)
5-19 years: 25% (22 of 88)
20+ years: 39% (30 of 77)

US: Measles Cases and Outbreaks | CDC   |  GLOBAL: Global Measles Outbreaks (cdc.gov)

Clinical Guidance

• Presentation: Consider measles in patients with fever and rash and ask about recent international travel, exposure to international travelers, or exposure to people with measles. Patients may have non-specific symptoms (fever, cough, coryza, conjunctivitis) without rash in the prodromal phase of infection, so heightened suspicion, particularly during local outbreaks or in patients with recent travel, can be key to timely diagnosis. The incubation period between exposure and initial symptoms is approximately 8-12 days. For images of rash see the Red Book chapter on Measles.
• Diagnosis:  Measles virus infection can be confirmed by: (1) detection of measles viral RNA by reverse transcriptase-polymerase chain reaction (RT-PCR); (2) detection of measles virus-specific immunoglobulin (Ig) M; (3) a fourfold increase in measles IgG antibody concentration in paired acute and convalescent serum specimens (collected at least 10 days apart); or (4) isolation of measles virus in cell culture.
• Who is at highest risk of acquiring measles infection:
• Unvaccinated children or adults
• Incompletely vaccinated (<2 doses of MMR) children or adults
• Individuals with known exposure to measles or recent travel to areas with active measles transmission.
• Who is at highest risk of severe measles infection or complications of measles:
• Infants and children aged less than 5 years
• adults aged more than 20 years;
• pregnant women;
• people with compromised immune systems, such as from cancer, chemotherapy, or HIV infection
• Complications: Measles can cause serious illness, even in previously healthy children. Complications of measles can include:
• Ear infections
• Diarrhea
• Pneumonia (either from measles virus itself or from bacterial superinfection)
• Encephalitis
• Death
• In addition, measles infection increases the risk of other severe infections for months or years after measles through the mechanism of immune amnesia.
• Precautions for patients with suspected or confirmed measles infection: Airborne precautions are needed whenever there is any suspicion of measles exposure. Promptly isolate, collect specimens, and report patients with suspected measles to public health.
• Prevention of measles: Vaccination is the cornerstone of measles prevention. All children should receive measles vaccination as part of the routine childhood vaccine schedule. Unimmunized or incompletely immunized children should begin catch-up vaccination as soon as possible. During an outbreak, MMR vaccine should be offered to all people with known exposure or in the outbreak community who lack evidence of measles immunity. During a community-wide outbreak that affects infants, MMR vaccine has been shown to be effective in preventing symptoms after exposure and may be recommended for infants 6 through 11 months of age. Children who receive their first MMR vaccine prior to 12 months of age will require two additional doses after 12 months of age for full protection. IGIM administered exposed, measles-susceptible people (not previously vaccinated or immunocompromised) will prevent or attenuate infection if administered within 6 days of exposure.
• Treatment: There is no specific antiviral agent for treatment of measles infection. Treatment of children with measles with oral vitamin A decreases measles-related morbidity and mortality. Dosing of vitamin A for treatment of children with measles can be found in the Red Book chapter on Measles.
• Reporting: Involvement of state and local health departments is often advisable for any suspected diagnosis of measles, as there may be specific ways these departments wish to receive specimens and manage patients.
• For more information see the Red Book chapter on Measles.

Watch this CDC video to learn more about the signs and symptoms of measles to quickly diagnose infected patients. Measles Clinical Features and Diagnosis - YouTube

Resources

• Red Book chapters: International Travel | Immune Globulin Intramuscular (IGIM)
• Red Book Online webinars:
  • Diagnosing Measles in the Pediatric Setting
  • Identifying Measles in the Pediatric Setting
• CDC: Measles (Rubeola)
• CDC COCA Now: Stay Alert for Measles Cases