An Outbreak of Rubella aboard a Ship of the German Navy

Abstract.

Background: During May and June 1996, an outbreak of rubella occurred offshore aboard a ship of the German Navy. The outbreak spread among 330 crew members over a period of 9 weeks, ending 2 days after the ship's return. This is the first detailed epidemiological investigation of a rubella outbreak on a ship, describing temporal progression, clinical manifestations, immunization status and seroprevalence of the population exposed.

Patients and Methods: Outbreak investigation using a questionnaire, health records and rubella serology (hemagglutination inhibition (HI) test and EIA).

Results: Of the 330 crew members 298 (90%) participated in the investigation. The outbreak was continuous without a peak and ended abruptly after the ship's return. It resulted in 20 cases, 11 of which were clinically symptomatic. A total of 35 (12%) crew members were susceptible to rubella prior to the outbreak, resulting in an attack rate of 57%. The highest risk for infection was linked to accommodation aboard the ratings deck (χ²-test, p = 0.004) with most favorable conditions of transmission. Only 9% of the participating crew were able to provide complete proof of their immunization status. The positive predictive value of a past history of rubella for the presence of antibodies against rubella was 59%.

Conclusion: The transmission of rubella that we describe aboard a ship was facilitated by the unusually close proximity of the crew and their insufficient immunity. Documentation of immunization was inadequate in this population.