This year, in 2025, more measles have been reported in 3 months than all of 2024.  As of March 20, 2025, a total of 378 confirmed measles cases were reported by 18 jurisdictions: Alaska, California, Florida, Georgia, Kansas, Kentucky, Maryland, Michigan, New Jersey, New Mexico, New York City, New York State, Ohio, Pennsylvania, Rhode Island, Texas, Vermont, and Washington..

According to the American Academy of Pediatrics, measles is an airborne virus transmitted by an infectious person when they cough, sneeze or breathe. Measles virus can remain infectious in the air up to two hours after an infected person leaves an area.  It is one of the most infectious known viruses. One infectious person can infect up to 18 others.

The only way to prevent a measles infection is vaccination.  One dose is 93% effective in preventing illness, and two doses is 97% effective.  It is recommended that children are inoculated for the first time between 12 to 15 months of age and the second dose administered between 4 and 6 years old.

The incubation period for measles is 10 to 14 days.  A person is most infectious 4 days before the rash appears and 4 days through 4 days after the rash appears.

Illness onset (high fever, cough, runny nose and red, watery eyes) begins a week or two after someone is infected. A few days later, a rash breaks out as flat, red spots on the face and then spreads down the neck and trunk to the rest of the body.

Other measles symptoms may include small spots in the cheek area inside the mouth, diarrhea and ear infection. Measles can lead to serious complications that may require hospitalization: pneumonia, swelling of the brain, deafness, intellectual disability and death. Measles can be serious for all ages, but children under the age of 5 are at the highest risk for serious complications.

Vaccinations for measles began in 1963 in the United States and it resulted in a “a greater than 99% decrease in the reported incidence of measles, with declaration of measles elimination.” (Red Book, AAP.org; https://doi.org/10.1542/9781610027373-S3_012_002). This declaration was the end of endemic measles.

As vaccination rates among school-age children have dropped communities are at risk for spread again.  According to Idaho Health and Welfare, when a community drops below a 95% vaccination rate, it is susceptible to an outbreak.  “In Idaho, only about 80.7% of kindergartners had records indicating receipt of two doses of MMR vaccine by the 2022-23 school year. Those are statewide percentages. In some communities, MMR vaccination may be even lower, increasing the risk of an outbreak if someone brings in measles.” (Idaho Health and Welfare, https://healthandwelfare.idaho.gov)