Mumps Virus : Secular Trends in the United States
Mumps became a nationally reportable disease in the United States in 1968. However, an estimated 212,000 cases occurred in the United States in 1964. Following vaccine licensure, reported mumps decreased rapidly. Approximately 3,000 cases were reported annually in 1983–1985 (1.3–1.55 cases per 100,000 population).
In 1986 and 1987, there was a relative resurgence of mumps, which peaked in 1987, when 12,848 cases were reported. The highest incidence of mumps during the resurgence was among older school-age and college-age youth (10–19 years of age), who were born before routine mumps vaccination was recommended. Mumps incidence in this period correlated with the absence of comprehensive state requirements for mumps immunization.
Several mumps outbreaks among highly vaccinated school populations were reported, indicating that high coverage with a single dose of mumps vaccine did not always prevent disease transmission, probably because of vaccine failure Since 1989 when two doses of MMR vaccine were recommended for school-aged children for improved measles control, the number of reported mumps cases steadily declined, from 5,712 cases in 1989 to 258 cases in 2004. In 2006, the United States experienced a multi-state outbreak involving 6,584 reported cases of mumps.
This resurgence predominantly affected Midwestern college students with the highest attack rates occurring among those living in dormitories. In the following two years, the number of reported cases returned to usual levels, and outbreaks involved fewer than 20 cases.
Beginning in June 2009, the largest U.S. mumps outbreak since 2006 has occurred. The index case was an 11 year old male infected in the United Kingdom, where approximately 7,400 reports of laboratory-confirmed mumps were received by the Health Protection Agency in 2009. A total of 3,502 outbreak-related cases were reported, primarily from New York. The outbreak was confined primarily to Orthodox Jewish communities, with less than 3% of cases occurring among persons outside these communities. The largest percentage of cases (53%) occurred among persons aged 5–17 years, and 71% of the patients were male. Among the patients for whom vaccination status was reported, 90% had received at least 1 dose of mumps-containing vaccine, and 76% had received 2 doses.
From December 2009, through December 2010, the U.S. Territory of Guam also experienced an outbreak, with 505 mumps cases reported; the median age was 12 years. Of the 287 school-aged children aged 6–18 years with reported mumps, 270 (94%) had received at least two doses of MMR vaccine, 8 (3%) had received one dose, 2 (1%) were unvaccinated, and 7 (2%) had unknown vaccination status. Two-dose MMR vaccine coverage in the most highly affected schools ranged from 99.3%–100%.
Like the mumps outbreaks that occurred in 2006, much of the 2009-2010 outbreaks occurred in congregate settings, where prolonged, close contact among persons facilitated transmission. Although school settings and large household sizes likely promoted transmission, the high vaccination coverage in the affected communities likely limited the size of the outbreaks. In addition, high vaccination coverage and less intense exposures in surrounding communities are the most plausible reasons that the few cases outside of the affected communities did not cause other outbreaks.
In 2011, there were 404 cases of mumps reported, and in 2012 there were 229 cases reported.
For information about the clinical case definition, clinical classification and epidemiologic classification of mumps see http://www.cdc.gov/vaccines/pubs/surv-manual/chpt09- mumps.html.
Mumps Virus : Secular Trends in the United States,Mumps Virus,Mumps Virus : Secular Trends,Secular Trends in the United States,Mumps Virus : Secular Trends
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