Measles, eliminated in the United States in 2000, is being reported again across several states, already surpassing the low report rate from 2023.
A warning went out from the Centers for Disease Control and Prevention (CDC) when data from Dec. 1, 2023, to Jan. 23, 2024, showed 23 confirmed measles cases in the United States. The number almost tripled two months later. In March 2024, Illinois saw its first measles cases reported in Cook, Will and Lake counties.
Now a year later, in April 2025, there have been 800 confirmed cases of measles in 25 states in the U.S., reports the CDC, including the first confirmed case in Illinois, according to the Illinois Department of Public Health.
Measles may be the most contagious virus we know of, and it can cause severe disease and long-term complications. The CDC estimates that nearly 1-3 of every 1,000 children who become infected with measles will die from complications.
The best defense against measles is vaccination.
Local health departments and providers are trying to educate the public about the importance of the measles, mumps and rubella (MMR) vaccine to prevent the spread of this highly contagious infectious disease.
To get the benefit of herd immunity, you need to have 95% of the population vaccinated, said Jennifer Burns, APRN, a skilled nurse practitioner who specializes in pediatric infectious diseases and partners with Endeavor Health through the Chicagoland Children's Health Alliance (CCHA).
“If more children and parents are not getting vaccinated, then we will see more incidents of all vaccine-preventable diseases, including measles,” Dr. Burns said.
How measles spreads
A virus in the nose and throat is the cause of measles, also known as rubeola. The virus is highly contagious and spreads via droplets in coughs and sneezes, as well as laughing, talking or singing.
If someone with measles is in a room, for up to about 90 minutes after, the droplets hover in the air and others in the room inhale them. A person who is unvaccinated or not immune has a 90% chance of contracting measles when exposed.
Symptoms of the measles include: fever, dry cough, nasal congestion, sore throat, conjunctivitis (inflamed eyes), mouth sores that are white with bluish-white centers (Koplik’s sign), and rash with large flat blotches.
A person is considered highly contagious for eight days total, four days before and four days after the telltale rash first appears.
An incubation period starts off the measles process 10-14 days before symptoms appear, with the first signs being a fever, cough, nasal congestion, sore throat and conjunctivitis.
Next comes the distinctive seven-day rash with a common spread pattern that starts on the face to the upper torso of the arms, chest and back moving down the lower torso from the thighs to the lower legs and feet. With the rash comes a high fever, sometimes reaching over 104 F (40 C).
As the rash fades, so do the other symptoms, leaving darkened or peeling skin.
Rare complications of the measles include blindness, pneumonia and encephalitis. While the measles death rate has been zero in the United States for many years, about 128,000 people, mostly children, die annually in developing countries from the virus.
“Your child may not die, but I cannot promise that they will not suffer complications from the measles virus,” Burns said.
“We do not have any medication to treat measles if your child is infected. When you get this infection, it lowers your immune system function with complications of encephalitis, diarrhea, hospitalization and death. Most of the measles complications are seen in children less than 5 years old and adults.”
If exposed to the measles, the only people who need to quarantine are unvaccinated individuals for 21 days from the time of the exposure.
The measles vaccine
The first version of the measles vaccine was available in 1963. Prior to that, the majority of children had the measles by the time they were 15 years old. At that time, 400-500 people died annually from the virus, with about 48,000 hospitalizations.
As a result of the MMR vaccination, childhood measles was eliminated in the United States in 2000. In the United States, it hit an endemic level in 2019 when more than 1,200 cases were reported across 31 states. This was the highest reportable incidence of measles since 1992, and the majority of cases were in those not vaccinated against measles.
The spread of measles stops with MMR vaccination. This particular vaccine, available since the 1970s, comes in two doses at ages 12-15 months and 4-6 years. The CDC reports a 97% effective rate with this vaccine schedule. Talk to your doctor about the importance of vaccinations and to review your vaccination records.
Burns says, “It is hard to predict when you will have an outbreak. The best studied time to give the measles vaccine is using our routine pediatric immunization schedule. If your child is not up to date, work with your provider to get your child’s vaccine.”
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