Bound for Sydney town: health surveillance on international cruise vessels visiting the Port of Sydney

The popularity and worldwide market for international cruises is growing; in 2000, 10 million people travelled on cruise ships worldwide, and this is expected to reach 22 million by 2010.1 However, cruise ships travelling in international waters have become increasingly recognised as a setting for infectious diseases outbreaks because of conditions that increase the chance of infection, such as presence of crew and passengers from many parts of the world, shared sanitation facilities, common food and drinking water supplies, exposure to air conditioning systems or water features potentially contaminated with legionella,2,3 and consumption of foods ashore where food safety standards may be poor. The semi-enclosed environment of the cruise ship facilitates rapid person-to-person spread of respiratory infection, such as influenza,4-6 or enteric infection, among which norovirus gastroenteritis has become prominent in recent years.7,8 A further consideration for the importance of disease control on cruise ships is that about a third of cruise passengers are older people, who may be more susceptible to infections and to complications arising from illness.4

A recent World Health Organization review of available information on outbreaks during 1970–2000 identified 108 enteric disease outbreaks affecting more than 16 000 people, and 50 legionella incidents comprising more than 200 cases. The authors acknowledged that many outbreaks are not reported and some may go undetected.1

Australian ports figure prominently in the itineraries of Pacific island cruises and, during the southern hemisphere summer, of around-the-world cruises. Sydney is the major Australian port of call for such cruises. Of the 207 visits to the major Australian ports (Cairns, Brisbane, Sydney, Melbourne, Hobart, Adelaide, Fremantle and Darwin) by international cruise ships carrying more than 215 000 passengers in the 2002–03 financial year, 88 visits (43%) were made to Sydney, accounting for 115 000 passengers (53%) (personal communications, port managers, 2004).

To assess the burden of disease occurring on cruise ships visiting Sydney and allow a timely and appropriate public health response to cases or outbreaks of disease on board, a system of routine health surveillance is necessary, tailored to the peculiar needs of international vessels.

In New South Wales, the Port of Sydney, comprising Sydney Harbour and Port Botany, falls within the jurisdiction of the South Eastern Sydney Public Health Unit (PHU). Over the past decade, but particularly since 1998, staff of the PHU have worked with Sydney-based shipping lines operating international cruises to improve health surveillance on cruise ships. The major change has been from reporting of quarantinable diseases only when a case occurs, to routine reporting of all infectious diseases of public health interest for every cruise, even when there are no cases. Although this reporting is voluntary, it is consistent with the requirements of the Public Health Act 1991 (NSW), the Quarantine Act 1908 (Cwlth) and the International Health Regulations (Box 1).

An “end-of-voyage medical report” is sent in the 24 hours before the ship berths in Sydney, and provides information on the vessel, cruise details, and crew and passenger complement; presentations to the medical centre for acute respiratory illness (ARI), influenza-like illness, pneumonia and gastroenteritis; hospitalisations; medical disembarkations; and deaths. This report used to be sent by fax to the PHU via the shipping agent’s Sydney office; it is now sent by email directly to designated PHU staff. With the advent of ready email communication from ship to shore, it has become routine for ships’ doctors to forward a series of progress reports during a cruise when there is concern about cases of disease or an outbreak.

The public health response varies depending on need. Information can be gathered from and advice provided to the ship at sea by email, satellite phone or fax. In most cases, a public health team with expertise in infectious diseases surveillance and response, epidemiology, environmental health, food safety and public health medicine meets the vessel shortly after it arrives in port. Team members speak with the ship’s doctor and staff officers, examine clinic records and any available documentation of the shipboard outbreak response, and conduct inspections of food-handling facilities, air conditioning systems and water supply as necessary. Interviews may also be conducted with passengers and crew, and appropriate clinical samples collected from those with recent illness (or from storage in the clinic) for processing by a public health laboratory.

In unusual cases, if an investigation is required urgently and the ship is still some days from an Australian port, the public health team may board the ship on the high seas. In most situations, the public health response is provided by the PHU in cooperation with the cruise ship operators and their land-based support staff, and in conjunction with the Australian Quarantine and Inspection Service (AQIS) and the NSW Health Department’s Communicable Diseases Branch.

Over the past decade, the South Eastern Sydney PHU cruise ship health surveillance program has provided a focal point for coordinated data gathering and response to public health concerns on Sydney-based cruise ships. The evolution of the program has led to a strengthening of relationships and communication protocols between the PHU, Sydney-based operators of cruise ships and the medical personnel that support them, the Sydney Ports Corporation, and AQIS. Expertise acquired by staff also informed the cruise ship vessel inspection and surveillance programs established for the Sydney Olympics.12,13

In practice, more open and earlier reporting of potential or actual public health issues on vessels has meant that the public health response may be more timely and effective. Moreover, public health staff have worked with vessel operators to:

• Educate ships’ doctors and masters of the need to report any case of infectious disease scheduled under the Quarantine Act;

• Strengthen the role of the medical clinic as the ship’s “surveillance office”, where data are routinely collected on illness and questionnaires are issued to patients if an outbreak is suspected;

• Advocate for improved preventive measures and messages, such as influenza vaccination of crew and inclusion of more comprehensive pre-travel vaccination advice to passengers in cruise brochures;

• Promote risk communication by the operators in the form of advisory letters to passengers during outbreaks and “pillow letters” advising incoming passengers of public health problems on the previous cruise;

• Encourage the waiving of professional medical fees by the major operator during outbreaks to remove this financial barrier to passengers’ use of the clinic (and thus to establishing the real extent of the outbreak); and

• Support the use in the medical clinic of rapid diagnostic kits for influenza,10 legionella and norovirus for earlier confirmation of the cause of outbreaks.

Finally, it is planned to negotiate with other operators of cruise ships using Sydney (and other Australian) ports to provide standardised end-of-voyage medical reports. A similar program has recently been initiated in Queensland, and discussions are underway towards a coordinated, national cruise ship surveillance program modelled on the Sydney program.