HEALTH TOPICS A TO Z

Ship sanitation and health

Shipping and health

A recently released World Health Organization (WHO) literature review¹ has identified over 100 disease outbreaks associated with ships since 1970. This is probably an underestimate because many outbreaks are not reported and some may go undetected. Such outbreaks are of concern because of their potentially serious health consequences and high costs to the industry. The main diseases associated with ships are gastrointestinal disease and Legionnaires' disease.

The passenger shipping industry (cruise ships and ferries) has expanded considerably in recent decades. In 2000, 10 million people travelled on cruise ships. This figure is expected to double by the year 2010.

The cargo shipping industry is also growing. It is estimated that 1.2 million seafarers are employed on general cargo vessels. Many spend months at sea, sometimes in remote regions of the world. Naval vessels also carry considerable numbers of crew, sometimes over 5,000 per ship.

Gastrointestinal disease

A wide range of pathogens affected passengers and crew during ship-associated gastrointestinal disease outbreaks. These included Vibrio parahaemolyticus, Salmonella species, Hepatitis A, enterotoxigenic Escherichia coli, enterohaemorrhagic Escherichia coli O157, Shigella species, Staphylococcus aureus, Norwalk-like virus (NLV), Cryptosporidium, Giardia lamblia and Cyclospora.
Most of the detected gastrointestinal disease outbreaks were associated with cruise ships and were linked to food or water consumed onboard ship. Factors contributing to outbreaks included contaminated bunkered water, inadequate disinfection of potable water, potable water contaminated by sewage on ship, poor design and construction of potable water storage tanks, deficiencies in food handling, preparation and cooking and use of seawater in the galley.
NLV is the most common pathogen implicated in outbreaks. Symptoms often start with sudden onset of vomiting and/or diarrhoea. There may be fever, abdominal cramps and malaise. The virus can spread in food or water or from person to person. NLV is a very infectious virus, and, in one outbreak on a cruise ship in 1998, over 80% of the 841 passengers were affected.
Outbreaks of acute gastroenteritis are also frequently reported aboard naval ships. One outbreak of viral gastroenteritis on a naval vessel in 1997 affected 1,806 (43%) crewmembers. Another outbreak of a waterborne infection in 1998 affected 200 crew or 22%. These outbreaks cause substantial morbidity among military personnel during deployment.
Very little information is available on the incidence of infection among seafarers on general cargo vessels. Many outbreaks and cases of infection probably go undetected. However, inspections on ships carried out in the year 2000 revealed that 9.2% had deficiencies relating to food and catering2.

Legionnaires' disease

Legionnaires' disease is a potentially fatal form of pneumonia, first recognized in 1976. The disease is normally contracted by inhaling legionella bacteria deep into the lungs. Legionella species can be found in tiny droplets of water (aerosols) or in droplet nuclei (the particles left after the water has evaporated).
The WHO review showed that over 50 incidents of Legionnaires' disease, involving over 200 cases, were associated with ships in the past three decades.
For example, an outbreak of Legionnaires' disease occurred on a single cruise ship in 1994: 50 passengers were affected on nine different cruises and one passenger died. The disease was linked to a whirlpool spa on the ship.
The problem is not restricted to passenger ships. Surveys carried out on general cargo ships have shown drinking water and air conditioning systems to be contaminated with Legionella pneumophila3.
Serologic surveys of seafarers on cargo ships have also shown that a high proportion have antibodies to Legionella pneumophila, suggesting that those on board ships are at increased risk of legionellosis compared with communities onshore3.
Control measures, such as proper disinfection, filtration and storage of source water, avoidance of dead ends in pipes and regular cleaning and disinfection of spas are therefore required to reduce the risk of legionellosis on ships.

International Health Regulations

The International Health Regulations (IHR), adopted by the World Health Organization (WHO) in 1969, provide a regulatory framework to support public health security by preventing the international spread of infectious diseases through permanent public health measures for travellers, cargo, and points of entry. These regulations replaced the 1951 International Sanitary Regulations.
The purpose of the IHR is to provide the maximum protection against the international spread of diseases with minimum interference with world traffic.
The current requirements of the IHR relate to provision of potable water at ports, public health inspections of ships, proper disposal of waste from ships, appropriate facilities for examining and isolating travellers and maintaining vector free zones and vector surveillance.
The IHR are currently being updated. It is proposed that the revised IHR cover both urgent and routine public health services at ports, airports and ground crossings.

WHO Guide to Ship Sanitation

The WHO Guide to Ship Sanitation4 is the official global reference on health requirements for ship construction and operation and is directly referenced in Article 14 of the IHR.
Its purpose is to standardize the sanitary measures taken in ships, to safeguard the health of travellers and to prevent the spread of infection from one country to another. The present edition of the Guide is based on the results of a survey of 103 countries and represents a synthesis of best national practice.

Revision of the Guide to Ship Sanitation

The Guide was first published in 1967 and was reprinted with minor amendments in 1987. The construction, design and size of ships have changed dramatically since the 1960s and the greatly increased level of transport by ships poses new hazards (e.g. Legionnaires' disease) that were not foreseen when the 1967 Guide was published.
Therefore, WHO is now updating the Guide in close collaboration with the International Labour Organization (ILO) and the International Maritime Organization (IMO).
A meeting was held in Miami, United States on 3-4 October 2001 to discuss and recommend the proposed contents of the revised Guide. Participants represented the ship building industry, cruise ship operators, seafarers associations, collaborating member states for the IHR, Port State Control, Port Health Authorities and other regulatory agencies attended. Experts from Australia, Brazil, Canada, Egypt, Finland, India, Morocco, the Netherlands, Norway, Russia, South Africa, Thailand, the United Kingdom and the United States are involved in the revision project.

Recommendations on the revised Guide

The meeting's participants recommended that the revised Guide should:

Apply to all ships including passenger ships, general cargo vessels, fishing vessels, naval vessels and tankers;
Cover preventive environmental health management including water supply at port, water production, treatment and distribution on ship, swimming and spa pools, waste disposal, food safety and vermin and vector control; and
Contain concluding chapters on disease surveillance, outbreak investigation, and routine inspection and audit.

The revised Guide will be based on a critical review of available evidence, including experience regarding effectiveness and feasibility of preventative and remedial measures.

The revised Guide is scheduled to be published in 2003.