As of May 17, there have been 880 cases of measles reported in the United States this year. While this case number pales in comparison to other areas of the world, it represents the highest number of cases in the U.S. in a single year since 1994 — and it’s only May. Due to successful vaccination and surveillance programs, measles was eliminated from the U.S. in 2000; however isolated cases and small outbreaks still occur. The current situation has been linked to exposure from countries experiencing much bigger measles outbreaks including Israel, Ukraine, and the Philippines, spreading domestically by transmission among unvaccinated and under-vaccinated people living in close-knit communities.   

Measles is a highly contagious viral infection transmitted person-to-person by respiratory droplets. The virus can live in the air or on surfaces for up to two hours after an infectious person has coughed or sneezed, making it among the most contagious pathogens known. The incubation period is 10-12 days, while the infectious period starts about four days prior to the onset of rash and lasts about eight days. Given the timing of symptomatology, an infected person can transmit the virus during the asymptomatic incubation period, contributing to the infectiousness of the virus.

Initial symptoms are vague and include fever, runny nose, cough, red eyes and sore throat. Physicians should make sure to check for Koplik spots in the oral mucosa of patients presenting with general upper respiratory infection symptoms, as it is a pathognomonic sign of measles. Two to four days after the fever starts, the characteristic rash arises first on the face and head, and spreads downward over the body. Suspected cases should be reported to local health authorities, and either an antibody test or reverse transcriptase-polymerase chain reaction (RT-PCR) can confirm the diagnosis.

The best way to prevent measles infection remains two-dose vaccination with live-attenuated MMR or MMRV.

Though some patients require hospitalization, there is no specific antiviral therapy available. Infection can cause serious complications including pneumonia and encephalitis, with long-term sequelae including blindness, deafness, cognitive decline, motor deficits, and seizures. Measles infection during pregnancy can lead to spontaneous miscarriage, prematurity, and low birth weight. Deaths due to measles have dropped substantially since implementation of widespread vaccination, but one person in about 1,000 infected with measles will succumb to the disease.

The best way to prevent measles infection remains two-dose vaccination with live-attenuated MMR or MMRV, which protects against measles, mumps, and rubella viruses, plus or minus varicella virus. The Centers for Disease Control and Prevention (CDC) recommend MMR or MMRV for all children first at 12-15 months and a second dose at four to six years of age. Two doses of either vaccine are about 97% effective at preventing measles (and quite protective against the other viruses).

Other select populations may benefit from vaccination. Adults without evidence of immunity (written documentation of adequate vaccination with live vaccine, laboratory confirmation of immunity or infection, or birth before 1957) should get at least one dose of MMR. Healthcare professionals without evidence of immunity should get two doses of MMR vaccine separated by at least 28 days. Additionally, those planning international travel should be protected against measles. Prior to travel, infants six to 11 months old should receive one dose of MMR vaccine (infants who get a dose prior to 12 months of age should get two additional doses), and children 12 months and older should receive two doses separated by 28 days. Teenagers and adults without evidence of immunity should get two doses separated by 28 days prior to travel.

Revaccination may be considered for some people who were originally vaccinated in the 1960s because a prior version of the vaccine was not effective. People with documentation of vaccination with either inactivated (killed) measles vaccine or measles vaccine of an unknown type prior to 1968 can be revaccinated with at least one dose of live-attenuated measles vaccine. 

While there have been more cases of measles in the U.S. this year than in any of the past 25 years, a long-standing vaccination program coupled with a well-resourced surveillance system prevents most imported cases from causing large outbreaks.


DynaMed Team

Infectious Disease, Immunology, and Rheumatology publishing group at DynaMed:

Vito Iacoviello, MD, Deputy Editor
Jill Angelosanto, PhD, Assistant Managing Editor
Karen Clarke, PhD, MS, Principal Editor, HIV
Heather D. Marshall, PhD, Senior Medical Writer
Anne Selig, PharmD, Clinical Writer
Jimmy DeRosa, MPH, Medical Writer
Muriel Herd, BS, Medical Writer