Measles is back in Idaho

October 6, 2023
Dr. Christine Hahn, Division of Public Health

Southwest Idaho is experiencing an outbreak of measles (“rubeola” or “red measles”), with 10 cases reported to date. Measles stopped being continuously spread in the United States in 2000. Only two cases of measles were reported in Idaho during the last 20 years, both in 2019.

Why are we worried about measles? Isn’t it a childhood disease that doesn’t last long?

Measles is a serious, highly contagious disease. Complications can lead to hospitalization, disability, and death.

  • About one in five unvaccinated people in the U.S. who get measles is hospitalized.
  • About one child in every 1,000 who get measles will have brain swelling that can cause seizures, permanent deafness, or intellectual disability.
  • About one to three of every 1,000 children with measles will die from lung and brain complications.
  • Measles may cause nonimmune pregnant women to give birth too soon or have a baby with a low birth weight.
  • A rare, fatal brain disease can occur seven to 10 years after an individual has measles, even if they appear to have fully recovered. About seven to 11 of every 100,000 individuals with measles could get this condition.

Complications from measles can occur in people of any age, but are more likely in:

  • Children younger than 5 years of age
  • Adults older than 20 years of age
  • Pregnant women
  • People with compromised immune systems, such as from leukemia or HIV infection

How did this measles outbreak happen?

The current measles outbreak in Idaho originated with an unvaccinated, nonimmune person who traveled to a country where there is an ongoing outbreak of measles. The person was exposed there and started having symptoms after returning to Idaho.

Several unvaccinated, nonimmune children were exposed to the first case in a household setting, and nine became ill with measles.

Because measles can be spread through the air, people seated near an infectious person on a plane or in a room,  or in a room within two hours after an infectious person, are considered exposed. Idaho public health officials are monitoring known exposed Idahoans. Nearly all were determined to be already immune except for an infant too young to receive vaccination against measles. None have had symptoms of measles to date. Although this is encouraging news, cases among unknown people exposed at one of the airports might yet be identified.

How can we prevent measles?

The most effective way to prevent measles is to get vaccinated against measles. The MMR vaccine protects against measles, mumps, and rubella. Two doses of the MMR vaccine are about 97% effective at preventing measles. Children 12 months through 12 years of age may get MMRV vaccine, which also protects against varicella (chickenpox). See measles vaccine recommendations at

Many countries abroad are reporting more measles cases. Make sure you and your loved ones are fully vaccinated at least two weeks before traveling abroad. Before travel, check if you are protected against measles or need a measles vaccine at

Call your healthcare provider if you or your child get sick with a rash and fever within three weeks after you return from abroad. This is especially important if you have a medical condition that prevents you from receiving MMR vaccine.

Could measles be continuously spread in the United States or Idaho again?

Yes. Several countries that had eliminated continuous spread of measles lost that status after 2019 because of ongoing outbreaks among the unvaccinated, nonimmune population. The United States almost lost measles elimination status the same year.

About 95% of a population needs to be immune from measles to prevent ongoing spread. The Centers for Disease Control and Prevention estimates that less than 95% of young children and adolescents are vaccinated against measles in Idaho and nationwide. 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.

Why has measles vaccination declined in Idaho?

Measles vaccination declined during the COVID-19 pandemic and after. Possible reasons for the decline during the pandemic include:

  • Difficulty accessing healthcare
  • Competing priorities
  • Increasing distrust of the government, science, and the health care industry and increasing disinformation and reliance on social media for information

How can barriers to measles vaccination in Idaho be overcome?

Routine childhood vaccines are available to Idaho children, under the age of 19 years, at no or significantly reduced cost. Your local public health district might offer MMR vaccine or can help refer you to a provider. Idaho’s Community Health Centers provide affordable access to healthcare for all ages. Medicaid participants can find a Healthy Connections Primary Care Provider by searching here. Find a free clinic near you and ask if they offer MMR vaccine. The Idaho Medical Association’s physician finder tool can also help.

If you are hesitant to have yourself or your child vaccinated, see credible sources of vaccine information and talk to your doctor. To help you evaluate sources of health information, see:

For more information about measles and MMR vaccine, see:

What are measles symptoms?

Typical initial symptoms of measles include a high fever, cough, runny nose, and red, watery eyes. Three to five days after those symptoms, a characteristic rash appears. Measles is highly contagious and can be spread for four days before and four days after the rash appears. Up to nine out of 10 nonimmune people who are exposed in a household will come down with measles.

Dr. Christine Hahn is Idaho’s state epidemiologist and the Division of Public Health’s medical director. She is board certified in infectious disease and works in an Idaho tuberculosis clinic twice monthly. She also serves on the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices.

Follow the Department of Health and Welfare on TwitterFacebook, and Instagram for updates and information you can trust.

The Idaho Department of Health and Welfare is dedicated to strengthening the health, safety, and independence of Idahoans. Learn more at 

Join the Discussion

Please note the following terms of participation in commenting on the DHW Voice blog.

To ensure a productive discussion you agree to post only comments directly related to this post and to refrain from posting obscenities; threatening, abusive or discriminatory language; sexually explicit material; and other material that would violate the law if published here; promotional content; or private information such as phone numbers or addresses. DHW reserves the right to screen and remove inappropriate comments.