Public health significance of chickenpox on ships - conclusions drawn from a case series in the port of Hamburg.

BACKGROUND Despite international notification requirements, the magnitude of disease transmission on board ships remains undetermined. This case series aims to exemplify that varicella aboard ships is a topic of interest for maritime medicine and of public health significance. MATERIAL AND METHODS Systematic presentation of cases of chickenpox reported to the Hamburg Port Health Authority between November 2007 and April 2008. A systematic literature search on 'ships and chickenpox' was performed. RESULTS Five crew cases of chickenpox were reported from two passenger ships and two cargo ships. The cases originated from Indonesia (2), the Philippines (1), and Sri Lanka (2). Three cases were notified by the shipmaster, one by a general practitioner, and one by the immigration service. Sources of infection were other crewmembers, passengers, and persons in the home countries. CONCLUSIONS This description of five varicella cases aboard ships points to the significance of the disease among seafarers. Many seafarers originate from tropical countries where seroconversion to varicella zoster virus generally occurs in late adolescents and adults. Thus, a substantial portion of the crew may be non-immune and have the potential to introduce the disease from their home country to the ship, or are at risk for infection on the ship. Port health authorities, shipmasters, and doctors need to be well informed about the relevance of chickenpox on ships and the recommended control measures. Travellers should be advised to report to the ship doctor with any signs of infectious disease.