Mumps resurgences in the United States: A historical perspective on unexpected elements☆
Introduction
Mumps is an infectious viral disease, classically manifested by inflammation of salivary glands and fever [1]. Mortality is rare, but aseptic meningitis can affect 10% of case-patients [2]. Mumps is an important cause of pediatric deafness, and up to 37% of post-pubertal males develop orchitis, 13% of whom have impaired fertility [1]. In the absence of vaccination, most persons have been infected by young adulthood [2]. In 1967 a live, attenuated mumps virus vaccine was licensed in the United States, and by 2005 high two-dose childhood vaccination coverage reduced disease rates by >99% [3], [4].
In 2006 the US experienced a multi-state outbreak involving 6584 reported cases, with the highest attack rate among persons 18–24 years of age, many of whom were college students [4]. In affected colleges, most case-patients had received a second dose of the measles–mumps–rubella vaccine (MMR) ≥10 years previously [5], [6]. This was the first large-scale US mumps outbreak among two-dose vaccinees.
Waning immunity appeared to play a role in facilitating this outbreak, consistent with effectiveness data from the United Kingdom [7] and serological data from Finland [8]. However, certain epidemiologic features were unexpected. The onset was sudden – a >50-fold rise in case counts within a 30-day period, followed by a sudden decrease, so that three-quarters of the epidemic's total cases occurred within 3 months [4]. After a decade in which the geographical distribution of mumps cases had been proportional to population, 85% of case-patients during the 2006 epidemic came from eight rural states located in the central US, followed by a return to an unremarkable geographic pattern [4]. In parallel, the peak age-specific attack rate shifted suddenly from primary school children to the college age group, then began moving back toward primary school children [4], [9].
Previous resurgences of vaccine-preventable diseases in the United States had not shown these characteristics. The 1989–1991 measles resurgence had been preceded in the mid-1980s by a rising tide of incidence and increasing mean age of disease acquisition [10]. Lasting for 3 years, the measles resurgence saw outbreaks distributed widely across the US, but incidence was most intense in urban, rather than rural, areas [10]. The pertussis resurgence of the 1990s differed markedly from measles in many respects, but it too was widely distributed across the US, without any clear rural focality, and showed a slowly progressive pattern, both in terms of incidence and changing age-distribution [11].
We reviewed the history of mumps disease reports in the US to assess whether the 2006 resurgence patterns should have been unexpected – or whether they reflected recurrent phenomena that might shed light on the behavior of the mumps virus in the population, thereby helping us to anticipate and prevent future epidemics.
Section snippets
Data sources
National notification of mumps cases was begun in 1922, discontinued in 1950 (though some states continued to report voluntarily), then restored in 1968 [12]. Where incidence was unavailable (1922–1967), we used the method of Sistrom and Mergo to scan graphic data four times, recorded the average value, and then used a cubic spline to interpolate missing values [12], [13]. In 1968, printed monthly case counts by state were available. Beginning in 1977, case-patients’ age group was increasingly
Pre-vaccine Period: 1917–1967
Irregular epidemic cycles of relatively moderate amplitude (mean peak/trough 1.6, range 1.1–2.5) had a periodicity of approximately 3 years, and a superimposed secular trend peaked during World War II (Fig. 1A). By age 14 years, approximately 90% of urban children had been infected, with peak incidence at age 5–9 years [12], [16], suggesting that millions of cases occurred each year, but reported incidence was much lower (50–251/100,000). Cases were reported throughout the year, with highest
Discussion
Many of the unexpected features of the 2006 mumps resurgence had occurred before in the history of mumps activity in the United States. Both the 1986–1987 and 2006 resurgences were immediately preceded by historic low points in disease activity. Both resurgences had extremely abrupt onsets, with incidence rising 10- to >100-fold over baseline within a month. In both resurgences, a few states contiguously located in the central US contributed most cases. In both the 1986–1987 and 2006
Acknowledgments
The authors wish to thank Janaki Kari, MS and Randall Young, MA for producing maps; Angelia Eick, PhD and Steven Tobler, MD for advising on military incidence; Hayley Hughes, MPH for providing military vaccination policies; Kathleen Gallagher, DSc and Gregory Armstrong, MD for supervisory guidance; and Jane Seward, MBBS for subject-matter expertise. We also express appreciation to all US state and local health departments for collecting and submitting surveillance data.
References (41)
- et al.
Mumps vaccine
- et al.
Mumps vaccination coverage and vaccine effectiveness in a large outbreak among college students—Iowa, 2006
Vaccine
(2008) - et al.
Forty years and four surveys: how does our measuring measure up?
Am J Prev Med
(2001) - et al.
Adolescent vaccination: coverage achieved by ages 13–15 years, and vaccinations received as recommended during ages 11–12 years, National Health Immunization Survey 1997–2003
J Adolesc Health
(2008) - et al.
Mumps outbreak in a highly vaccinated population
J Pediatr
(1991) - et al.
Incidence of mumps and immunity to measles, mumps and rubella among US military recruits, 2000–2004
Vaccine
(2008) - et al.
ELISA underestimates measles antibody seroprevalence in US military recruits
Vaccine
(2008) Infectiousness of communicable diseases in the household (measles, chickenpox, and mumps)
Lancet
(1952)- et al.
Mumps and mumps vaccine: a global review
Bull World Health Organ
(1999) Mumps vaccine
MMWR Morb Mortal Wkly Rep
(1967)
Recent resurgence of mumps in the United States
N Engl J Med
Mumps vaccine performance among university students during a mumps outbreak
Clin Infect Dis
Vaccine effectiveness estimates, 2004–2005 mumps outbreak, England
Emerg Infect Dis
Persistence of measles, mumps, and rubella antibodies in an MMR-vaccinated cohort: a 20-year follow-up
J Infect Dis
Mumps epidemiology in the United States (US) before and after the 2006 outbreak
Epidemiology of measles in the United States in 1989 and 1990
Pediatr Infect Dis J
Changing epidemiology of pertussis in the United States: increasing reported incidence among adolescents and adults, 1990–1996
Clin Infect Dis
A simple method for obtaining original data from published graphs and plots
Am J Roentgenol
Age incidence of the common communicable diseases of children
Pub Health Rep
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The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention, US Department of Health and Human Services.