At the beginning of May, I received an update from the Maryland Department of Health about measles activity in our state. While we were not having an outbreak, the number of cases had increased to 3 for 2026. Like many of us, I have also been watching and reading with concern as measles cases and exposures continue to increase in the United States. In 2025, the Centers for Disease Control (CDC) reported 2288 cases in the United States, the highestnumber recorded since 1991. Since 2000, the number of measles cases has only occasionally surpassed 500 cases per year (in 2014 and 2019). So far in 2026, 2104 cases have already been reported in the U.S., meaning that we are on track to have another record year for measles cases.
For many people, measles may sound like an illness from another era. For those of us in medicine, it is a reminder that vaccine-preventable diseases can return quickly when community protection weakens.
How does measles spread and what does infection look like?
Measles is spread through the air when a sick person coughs or sneezes. Interestingly, the virus can stay in the air for up to two hours even after the infected person has left the space. It is also highly contagious and one person can infect up to 90% of nearby unprotected individuals. Put another way, asingle contagious person can spread the virus to between 12 and 18 other people.
Symptoms of measles typically begin 7-14 days after exposure, during which the virus is incubating and replicating. The disease usually begins with a high fever (>104° F) which is followed by the “three C’s” of cough, coryza, and conjunctivitis. Koplik spots, tiny white spots with bluish-white centers, may appear inside of the mouth. Finally, the distinctive red, maculopapular rash appears, beginning on the hairline and face and spreading downward to the trunk and extremities.
Why should we take measles seriously?
As I mentioned above, measles is one of the most contagious infections. Adding to the problem, a patient is contagious before any signs or symptoms appear. Aside from the cold-like symptoms and rash, measles infection can have significant sequelae. The most common are ear infections and diarrhea. If severe, ear infections may lead to hearing loss. Pneumonia is another complication of measles infection and the leading cause of death in children with measles infection. Acute encephalitis and subacute sclerosing panencephalitis (SSPE) can also develop. SSPE is a rare but fatal progressive neurologic disease that typically presents about 7 or more years after initial measles infection, but can occur decades after initial exposure. There is a higher incidenceof SSPE in children who are initially infected with measles before the age of 2. Initially, an individual may present with mild mental deterioration such as memory loss or behavioral changes. Then, the patient will progress to myoclonic seizures, motor disability and eventually a persistent vegetative state. Death typically occurs 1-3 years after diagnosis.
Measles infection in pregnancy is particularly dangerous and can lead to severe maternal complications such as pneumonia, miscarriage, stillbirth, preterm delivery, intrauterine growth restriction and congenital measles.
During the initial measles infection, supportive care is often the only recommended treatment. Ribavirin, a broad-spectrum antiviral medication, can be given to those with severe disease and complications. It is important to note that there is no specific antiviral medication for measles.
Measles Vaccination
The measles vaccination was first licensed in 1963. By 1971, the MMR vaccine was licensed and it included vaccines for measles, mumps and rubella. Studies have found this vaccine to be extremely efficacious with 93% protection with just one dose and 97% protection with 2 doses. In the United States, the first dose is given at 12-15 months of age, and the second is given between 4-6 years of age, before the child attends school. Because the MMR vaccine is a live, attenuated vaccine, there are contraindications to it including pregnancy, history of hematologic malignancy, current chemotherapy use, long-term immunosuppression and a history of a severe allergic reaction.
Laboratory Diagnosis
The gold standard for confirming a diagnosis of measles is real-time polymerase chain reaction (RT-PCR) testing. The CDC currently recommends BOTHserologic testing and RT-PCR testing for confirmation of measles infection. RT-PCR testing can be performed on serum or nasopharyngeal or oropharyngeal swabs. These specimens are ideally collected within 3 days of rash onset. Serology is useful for identifying both infection and immunity. Measles IgM is elevated 1-3 days after the onset of the rash and can be detected for up to 6-8 weeks. IgG appears a few days after IgM. For the diagnosis of measles, both IgG and IgM should be tested along with RT-PCR testing. IgM testing alone for diagnosis can be problematic, especially in settings with a low incidence of measles. IgM can have cross-reactivity with HHV-6 and parvovirus, infections which also can cause rashes.
If a question regarding a patient’s immunity to measles arises, IgG testing alone is appropriate.
The Bottom Line
Measles is a preventable illness, and vaccination is safe and important. We can all be a part of a healthier and safer environment when we vaccinate ourselves and confirm that we are vaccinated or immune to measles. This is especially important before we travel, before we get exposed, and before an outbreak reaches our community. From the medical and laboratory perspective, testing for immunity or early exposure leads to a healthier community. This is important not just for individuals with measles, but also important for those who cannot be vaccinated like newborns, cancer patients, transplant recipients, pregnant patients and others who rely on community immunity for protection. all find something useful in the course.