A 2009 outbreak of mumps in the USA that primarily affected Orthodox Jewish teenage boys may have been perpetuated by close schooling conditions, say the authors of a study published in TheNew England Journal of Medicine.
Albert Barskey (Centers for Disease Control and Prevention, Atlanta, Georgia, USA) and colleagues explain that the chavrusa style of schooling, where boys spend up to 15 hours a day studying closely with multiple work partners, could explain why the disease affected this group without spreading to other populations.
"The high proportion of cases among males attending yeshivas [single-sex religious schools] in this study suggest that a high-density setting, in which there are certain behaviors that facilitate transmission of the virus, may overwhelm existing antibody levels," they write.
Notably, Orthodox girls, who attend conventional schools, and non-Orthodox persons were affected to a much lesser extent.
The authors used data received by the Centers for Disease Control and Prevention showing that between June 2009 and June 2010, 3502 cases of mumps were reported from multiple communities in New York and New Jersey.
In all, 97% of the cases occurred in Orthodox Jewish persons, and 71% were in males. Just over a quarter occurred in adolescents between 13 and 17 years of age.
The Orthodox Jewish population had similar mumps, measles and rubella (MMR) vaccine coverage to the surrounding communities. In patients whose vaccination status was known, 76% had received the recommended two doses of the vaccine, as had 89% of the adolescents who were infected.
However, the authors found that patients who had been vaccinated experienced fewer common complications. For example, orchitis occurred in 7% of patients aged 12 years and over, but the rate significantly differed between vaccinated and unvaccinated patients (7 vs 4%). Similarly, rates of deafness, meningitis and oophoritis in female patients were less common in vaccinated patients, although this did not reach statistical significance.
The authors say that their findings underline the importance of vaccination programs.
"There remains an ongoing threat of imported infections and of endemic transmission of mumps virus. The outbreak reported here highlights that importance of maintaining a high rate of two-dose MMR vaccine coverage in all communities," they conclude.
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