Measles, Mumps, and Rubella Disease Issues
What is the current situation with measles, mumps, and rubella in the United States?
Since 2000, when measles was declared eliminated from the U.S., the annual number of cases has ranged from a low of 37 in 2004 to a high of 667 in 2014. The majority of cases have been among people who are not vaccinated against measles. Measles cases in the United States occur as a result of importations by people who were infected while in other countries and from transmission that may occur from those importations. Measles is more likely to spread and cause outbreaks in U.S. communities where groups of people are unvaccinated. A provisional total of 122 measles cases was reported in 2017.
Since the pre-vaccine era, there has been a more than 99% decrease in mumps cases in the United States. However, outbreaks still occasionally occur. In 2006, there was an outbreak affecting more than 6,584 people in the United States, with many cases occurring on college campuses. In 2009, an outbreak started in close-knit religious communities and schools in the Northeast, resulting in more than 3,000 cases. Since 2015, numerous outbreaks have been reported across the US, in college campuses, prisons, and close-knit communities, including a large outbreak in northwest Arkansas where almost 3,000 cases were reported in 2016. These outbreaks have shown that when people with mumps have close contact with a lot of other people (such as among students living in dormitories and students and families in close-knit communities) mumps can spread even among vaccinated people. However, outbreaks are much larger in areas where vaccine coverage rates are lower. A provisional total of 5,629 mumps cases were reported in 2017.
Rubella was declared eliminated (the absence of endemic transmission for 12 months or more) from the United States in 2004. Fewer than 10 cases (primarily import-related) have been reported annually in the United States since elimination was declared. Rubella incidence in the United States has decreased by more than 99% from the pre-vaccine era. A provisional total of 9 rubella cases and 2 CRS cases were reported in 2017.
How serious are measles, mumps, and rubella?
Measles can lead to serious complications and death, even with modern medical care. The 1989–1991 measles outbreak in the U.S. resulted in more than 55,000 cases and more than 100 deaths. In the United States, from 1987 to 2000, the most commonly reported complications associated with measles infection were pneumonia (6%), otitis media (7%), and diarrhea (8%). For every 1,000 reported measles cases in the United States, approximately one case of encephalitis and two to three deaths resulted. The risk for death from measles or its complications is greater for infants, young children, and adults than for older children and adolescents.
Mumps most commonly causes fever and parotitis. Up to 25% of persons with mumps have few or no symptoms. Complications of mumps include orchitis (inflammation of the testicle) and oophoritis (inflammation of the ovary). Other complications of mumps include pancreatitis, deafness, aseptic meningitis, and encephalitis.
Rubella is generally a mild illness with low-grade fever, lymphadenopathy, and malaise. Up to 50% of rubella virus infections are subclinical. Complications can include thrombocytopenic purpura and encephalitis. Rubella virus is teratogenic and infection in a pregnant woman, especially during the first trimester can result in miscarriage, stillbirth, and birth defects including cataracts, hearing loss, mental retardation, and congenital heart defects.
What are the signs and symptoms healthcare providers should look for in diagnosing measles?
Healthcare providers should suspect measles in patients with a febrile rash illness and the clinically compatible symptoms of cough, coryza (runny nose), and/or conjunctivitis (red, watery eyes). A clinical case of measles is defined as an illness characterized by
a generalized rash lasting 3 or more days, and
a temperature of 101°F or higher (38.3°C or higher), and
cough, coryza, and/or conjunctivitis.
Koplik spots, a rash present on mucous membranes, are considered pathognomonic for measles. Koplik spots occur from 1 to 2 days before the measles rash appears to 1 to 2 days afterward. They appear as punctate blue-white spots on the bright red background of the buccal mucosa.
Providers should be especially aware of the possibility of measles in people with fever and rash who have recently traveled abroad or who have had contact with international travelers.
Providers should immediately isolate and report suspected measles cases to their local health department and obtain specimens for measles testing, including viral specimens for confirmation and genotyping. Providers should also collect blood for serologic testing during the first clinical encounter with a person who has suspected or probable measles.
How contagious are measles, mumps, and rubella?
Measles is highly infectious. It is primarily transmitted from person to person via large respiratory droplets. Airborne transmission via aerosolized droplets has been documented in closed areas (such as an office examination room) for up to 2 hours after a person with measles occupied the area. Following exposure, more than 90% of susceptible people develop measles. The virus can be transmitted from 4 days before the rash becomes visible to 4 days after the rash appears. The contagiousness of mumps is similar to that of influenza and rubella but is less than that for measles or varicella.
How long does it take to show signs of measles, mumps, and rubella after being exposed?
For measles, there is an average of 10 to 12 days from exposure to the appearance of the first symptom, which is usually fever. The measles rash doesn't usually appear until approximately 14 days after exposure, 2 to 4 days after the fever begins. The incubation period of mumps averages 16 to 18 days (range: 12 to 25 days) from exposure to onset of parotitis. The incubation period of rubella is 14 days (range: 12 to 23 days). However, as noted above, up to half of rubella virus infections are subclinical.
What are the current recommendations for the use of MMR vaccine?
The most recent comprehensive ACIP recommendations for the use of MMR vaccine were published in 2013 and are available at www.cdc.gov/mmwr/pdf/rr/rr6204.pdf. MMR vaccine is recommended routinely for all children at age 12 through 15 months, with a second dose at age 4 through 6 years. The second dose of MMR can be given as early as 4 weeks (28 days) after the first dose and be counted as a valid dose if both doses were given after the child's first birthday. The second dose is not a booster, but rather is intended to produce immunity in the small number of people who fail to respond to the first dose.
Adults with no evidence of immunity (evidence of immunity is defined as documented receipt of 1 dose [2 doses 4 weeks apart if high risk] of live measles virus-containing vaccine, laboratory evidence of immunity or laboratory confirmation of disease, or birth before 1957) should get 1 dose of MMR unless the adult is in a high-risk group. High-risk people need 2 doses and include healthcare personnel, international travelers, and students at post-high school educational institutions.
Persons who previously received a dose of MMR vaccine in 1963–1967 and are unsure which type of vaccine it was, or are sure it was inactivated measles vaccine, should be revaccinated with either one (if low-risk) or two (if high-risk) doses of MMR vaccine. At the discretion of the state public health department, anyone exposed to measles in an outbreak setting can receive an additional dose of MMR vaccine even if they are considered complete for their age or risk status.
How does being born before 1957 confer immunity to measles?
People born before 1957 lived through several years of epidemic measles before the first measles vaccine was licensed in 1963. As a result, these people are very likely to have had measles disease. Surveys suggest that 95% to 98% of those born before 1957 are immune to measles. Persons born before 1957 can be presumed to be immune. However, if serologic testing indicates that the person is not immune, at least 1 dose of MMR should be administered.
Why is a second dose of MMR necessary?
Between 2% and 5% of people do not develop measles immunity after the first dose of vaccine. This occurs for a variety of reasons. The second dose is to provide another chance to develop measles immunity for people who did not respond to the first dose.
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