Potential hazards for blood-borne infections and sexually transmitted diseases include accidents and injuries, unsafe medical care provided to seafarers in ports in highly endemic areas, accidental injuries during medical procedures on board, unsafe blood transfusions, tattooing, piercing and unprotected sex.

Sexually transmitted diseases in seafarers

(see also for more detail Chapter 17)

Seafarers have traditionally been seen as a special risk group for acquiring and spreading sexually transmitted diseases, as indicated by the Brussels International Agreement of 1924 which requires state parties to provide free medical services to merchant seamen for the treatment of syphilis, urethritis of any aetiology, chancroid, lymphogranuloma venereum, granuloma inguineale and any other venereal diseases.[10] In 1993 the common committee of the International Labour Organization and the World Health Organization identified Hepatitis B and Human Immunodeficiency Virus Infection / Acquired Immunodeficiency Syndrome as infectious diseases against which there should be provisions for guidance on prevention.[11] The Maritime Labour Convention 2006 emphasizes the need for HIV/AIDS prevention targeted at merchant seamen.[12] The International Maritime Health Association and the International Trade Federation issued a statement in 2008 in which the organizations advocate against selection for employment based on HIV status.[13]

Hepatitis B virus

Hepatitis B virus (HBV) infections occur worldwide. Blood, saliva and semen are infectious. One third of the world population is infected. The majority of acute hepatitis B infections remain asymptomatic, 30-50% of adults present with an acute illness with jaundice, fevers and abdominal pain. Incubation period is usually 45 to 180 days. All individuals who are HbsAg positive are potentially infectious.

Transmission occurs by percutaneous (intravenous , subcutaneous, intramuscular, intradermal) and mucosal exposure to infective body fluids. Major modes of HBV transmission include sexual or close household contact with an infected person, perinatal mother-to-infant transmission, injecting drug use, piercing and tattooing and nosocomial transmission. The case fatality rate is about 1%, but higher in those of over age 40. In a small fraction of adults infected with hepatitis B virus, chronicity with severe complications such as liver cirrhosis, liver failure and hepatoma develop after decades.

A recombinant vaccine is available which protects from acute and chronic infection and is recommended by the World Health Organization for at-risk groups and for inclusion in childhood vaccine schedules[14]

A study of 2072 male United States naval personnel done in 1989 showed that the prevalence of the hepatitis B marker anti-HBc in military personnel was comparable to that in a concurrent survey of the United States civilian population. Presence of anti-HBc was independently associated with age, black or filipino race, foreign birth, a history of sexually transmitted disease and South Pacific / Indian Ocean deployment.[15]

A retrospective longitudinal study from a Danish research database containing all seamen who had been employed on Danish ships between 1986 and1993  and the National Registry for Notifiable Diseases found that the standardised incidence ratio for  hepatitis B Virus infection among male sailors compared to the general population was 3.2 (95% CI:1.79-4.78). The main mode of transmission was intravenous drug use.[16]

Bellis and co-workers in a prevalence study conducted among sailors arriving at the port of Liverpool in the United Kingdom found a 12 % prevalence of the hepatitis B marker anti- Hbc among a study population of 291 sailors. Sailors from Asia had a higher prevalence of seropositivity when compared with colleagues from Western Europe, and North America.[17]

A clinic based prevalence study from Spain in  1998 assessed 2348 seafarers attending health clinics who were examined for evidence of hepatitis. Out of the 98 symptomatic cases 50 (2.1% of study population) carried anti- HBc-, signifying contact to hepatitis B Virus during their lifetime.[18]

A cross sectional study conducted among 95 Vietnamese civilian and military seafarers and 45 other maritime workers in the city of Haiphong showed that 58% (55/140) persons in the study population were positive for HBsAg and Anti-HBs. The authors concluded that Vietnamese seamen are a high risk group for hepatitis B infection.[19]

A survey of 103 seafarers attending a training course for medical care on board in Denmark showed that the seamen responsible for medical care on board in the absence of a medical doctor do have a risk of exposure to blood and body fluids. Over a 10-year period 19 out of 103 persons reported contact with blood, including 4 accidents with needles, 23 persons had been in contact with other body fluids and hence at a potential risk of infection.[20]

In Georgia, a nation that supplies a large number of seafarers to the global market, hepatitis B virus infection is assessed as part of the pre-employment exams. It was found that 6.5% of 1165 male Georgian seafarers were tested positive for HBs Antigen.[21]

Overall, available studies do not allow estimates to be made to show whether seafaring is associated with a higher risk of hepatitis B infection. The results mainly reflect the epidemiology of hepatitis B infection and availability of routine immunization in the country of origin of the seafarer.

Chronic hepatitis B infection with no signs (clinical and lab studies) of hepatic impairment and a confirmed low level of infectivity should not restrict a seafarers’ fitness to work.[22]

If a chronic hepatitis B infection is accidentally detected during the pre-employment exam, the clinician will have to counsel the patient on further diagnostic and treatment options. The urgency of diagnostic and possibly therapeutic requirements depend on factors including  liver function and the availability of therapy in the country. [23]

All hepatitis B sAg positive persons are potentially infectious; the level of infectivity varies with the viral load. There is a marginal risk of transmission of Hepatitis B from living and working together on a ship. However, medical care and first aid pose more specific risks of transmission from possible blood contact.

As a consequence, in the individual risk assessment and pre-travel counselling of seafarers several risk factors for acquiring hepatitis B infection need to be addressed:

- Risk of infection during first aid and medical care by nautical officers on board,

- Risk of nosocomial infection with Hepatitis B from unsafe blood products and a variety of medical procedures (injections, dental care, endoscopy, surgery etc.) in port medical facilities

- Unprotected sexual intercourse

- Piercing and tattooing

Generally, full pre-travel immunization of all seafarers against hepatitis B is warranted.

Furthermore, safety precautions to prevent blood-borne infections from first aid and medical care on board (personal protective equipment such as gloves, safety cannulas, sharps containers) and on careful choice of medical care ashore if possible, as well as continuous information on the risks of unprotected commercial or other sex  These are the responsibility of the ship owners/operators and can reduce the risk of infection with hepatitis B and C. They will also reduce the risk of  HIV and other infections.

Human Immunodeficiency Virus and Acquired Immunodeficiency Syndrome (HIV/AIDS)

Acquired Immunodeficiency Syndrome (AIDS) is caused by Human Immunodeficiency Viruses 1 and 2 (HIV 1/2) which damage the immune system and make affected person more vulnerable to infections and to other diseases such as cancer.

AIDS is recognized to be a major public health problem throughout the world. It is now known that the patterns of the epidemic differ between regions. In some parts of the world, such as North America, Europe or the Philippines it mainly affects certain risk groups such as i.v. drug users, immigrants or homosexuals but is also a threat to the general population. In other parts of the world, such as Central, Eastern and Southern Africa and some countries of the Caribbean it is primarily seen in heterosexuals. Countries and regions such as Eastern Europe, China or India are facing new public health challenges due to HIV.

HIV is present in the majority of body fluids of an infected person. Most infections result from contact with semen and vaginal secretions, blood and blood products from a person infected with the virus. Potential hazards of infection include accidents and injuries, unsafe medical care provided to seafarers in ports of high endemic areas, performance of medical procedures on board, unsafe blood transfusions, tattooing, piercing and unprotected sex. HIV cannot be transmitted through social or workplace contact with an infected person; there are no documented cases of transmission through kissing.

In the last decade the risk of infections through different sex practices has been studied in detail showing that the often cited value of 0.001 transmissions per 1000 contacts represents a lower bound with a high variability due to transmission cofactors such as circumcision or genital ulcer disease. While risk of disease transmission is highest in early stages of infection, treatment of the disease with successful lowering of the viral load is now recognized as a powerful public health tool that reduces the risk of transmission.

Cure of HIV infection is not possible, but effective treatment options for HIV infection have existed for more than a decade and new ones are constantly being introduced. For most persons to whom this treatment is available, HIV has turned from an acute into a chronic condition. This requires life-long adherence to antiviral medication. The infected persons will usually be perfectly well for several years after infection. During this time the CD 4 count, a marker of infection, will decline slowly over the years. However latency time from infection to the point when treatment in needed is highly variable due to genetic factors, exposure to infections and general living conditions. Generally speaking treatment is begun when damage to the system has reached a potentially dangerous level. Strict adherence to therapy and close monitoring of side-effects and immune-status by a specialist are essential for a successful outcome.

Work related risk of HIV infection in sailors

Mobile transport workers, mainly truck-drivers, played a major role in spreading the disease in Africa and India in the evolving global pandemic. Very early in the epidemic HIV/AIDS affected the community of seafarers. Later analysis of blood samples taken during the course of disease revealed that as early as the 1950´s an English seafarer died of AIDS. This was also the case in the late 1960s with a Norwegian seaman and his family. 

Hansen et al estimated the risk of HIV infection in seafarers by an analysis of medical records from the main HIV treatment centres in Denmark. The risk of HIV infection in seafarers was estimated in comparison to the general Danish population up to the end of 1992. The incidence of HIV infection for Danish seafarers was estimated to be 0.000016 cases/person-year. This was eight times higher than in the general Danish population. The authors found that most infections in seafarers were acquired heterosexually early in the epidemic in high-endemicity areas.[24]

A study published in 1992 conducted among a sample of 561 Spanish seafarers seeking attention prior to travelling abroad confirmed HIV-1 infection in 4% of seafarers.[25]

A questionnaire survey from Croatiaperformed in Rijeka in 1989 to 1990 demonstrated that seafarers had inadequate knowledge about the routes of HIV transmission and rarely used condoms for protection against HIV infection.[26]

2 positive cases of HIV in African seafarers visiting a port in Belgium were identified among 599 sailors in the early nineties.[27]

Demissie and co-workers reported 1996 in a cross-sectional study in 260 Ethiopian sailors found an HIV-1 prevalence of 9.6%  as assessed by blood-testing.[28]

Bellis and co-workers performed saliva testing for HIV antibodies in 304 sailors whilst in Liverpool, United Kingdom. A 0.33% prevalence of anti-HIV was reported.[17]

A study from Poland analyzed serological HIV tests from 1992 to 1996. From 26,988 tests performed in seafarers HIV antibodies were detected in 11 seamen and 3 deep-sea fishermen (0.05%).[29]

In the Philippines a questionnaire was handed to seafarers who presented at manning agencies from August 1997 to March 1998. The results showed that 52% of 300 respondents admitted extramarital sexual encounters.[30] A 2005 report from the Department of Health of the Philippines, which supplies the largest number of seafarers of any country globally, analysed 2250 HIV positive cases. 745 were Filipino overseas workers including 36% seafarers. The main mode of transmission was sexual.[31]

An analysis of the central register of HIV/AIDS infections from Montenegro in 2007 indicated that 15% of the total of 68 notified HIV infected persons in Montenegro were seafarers by profession. It is suggested that there are about 6000 professional seafarers in Montenegro.[32]

HIV risk behaviour was studied in Seafarers from Thai Communities. They found in a group of 1603 Seafarers that only 17% were married. 33% had visited a female sex worker in the last year, of those 19% reported some previous drug use.[33]

Despite the relatively low prevalence of HIV infection in seafarers as compared to transport workers in some regions, seafarers are a vulnerable occupational group for sexually transmitted infection. The following risk factors for HIV infection are identified: decreased or absence of access to HIV information, barriers to voluntary testing and counselling, likelihood of engaging in risky sexual practices, separation from spouses and families, alcohol use, time spent in high prevalence regions.[34]

Employment and HIV/AIDS

The International Labour Organisation has published an “ILO Code of Practice on HIV/AIDS and the World of Work” in 2001 where the organisation advocates for the continuation of employment regardless of HIV status. However, the ship as a work place has always been seen as a special entity due to the limited access to diagnosis and therapy while on board.

Dahl evaluated the workplace policies of cruise ship companies concerning HIV positive crew on ships. He found a variety of practices, about half of the 15 companies responding require pre-sea HIV testing, some to avoid hiring HIV+ seafarers, others to establish HIV as a pre-existing condition or to ensure proper follow up of the HIV infected seafarers.[35]

The decision on the fitness of a HIV positive person for duty on board is complex and involves in depth knowledge of the natural course of disease, treatment options and living conditions at sea.  The Handbook for Seafarers´Medical Examiners gives detailed advice on the best means for taking  decisions on fitness to work at sea.[36]

The main concern when taking fitness decisions in relation to HIV infection is the increased risk to the individual due to a lack of access to medical diagnosis and care. Risks to other crew members are negligible if standard precautionary measures are observed and these mainly concern medical care and first-aid aboard.

Post-exposure prophylaxis with accidental exposure to blood and other fluids

HIV infection can be prevented after a contact with body fluids from an HIV infected person. Drugs effective against HIV must be given as soon as possible after a risk-exposure to the virus. Post-exposure prophylaxis, if taken correctly reduces the risk of infection by 80%.  Exposure may occur from accidental exposure to body fluids during medical care and first aid, but also from unprotected sex. For this reason Anti-HIV medication is now recommended by the WHO to be carried as part of the ship’s medical chest.[37] However, no specific recommendations for the best use of post-exposure prophylaxis in the marine environment have been agreed. Most recommendations have been developed for the health care sector or for high risk sexual encounters (such as commercial sex). The use of post-exposure prophylaxis must remain an individualized decision depending on the specific circumstances. It can be safely assumed that the risk for seafarers providing first-aid on board is lower than for health care workers in high prevalence countries. However, unprotected heterosexual or homosexual commercial sex in a high prevalence country (such as South Africa) justifies post exposure prophylaxis. Post-exposure prophylaxis is no substitute for availability of condoms and preventative messages to seafarers.

General rules for the use of antiretroviral post-exposure therapy in an injury during first aid are:

- Immediately remove as much as possible of the body fluid

If a high risk exposure is suspected and no medical advice is available start antiretroviral prophylaxis if possible within 2 hours, otherwise consult a medical specialist before the start of treatment. Starting post-exposure prophylaxis more than 72 hours after exposure is not effective and should not be done. Consult a specialized medical doctor or radio-medical advice as soon as possible for continuation of prophylaxis (typically taken for 30 days).


Table 3. Classification of risk of transmission after exposure to HIV

Other Sexually Transmitted Diseases

The systematic search did not reveal any studies on sexually transmitted diseases known to be of significance in international travel including Chlamydia trachomatis, syphilis, gonorrhea, chancroid, donovanosis, Herpes genitalis and others after 1989.

Hepatitis C infection

Hepatitis C virus infection occurs worldwide. Population seroprevalence differs between low – income countries and high income countries. Most populations in Africa, the Americas Europe and Southeast Asia have prevalence rates under 2.5%. Prevalence rates for the Western pacific regions average 2.5 -4.9%. In the Middle East, the prevalence of anti-HCV ranges from 1% to more than 12%.

The main mode of transmission is via reused or shared injections, piercing or tattooing utensils, contaminated blood products or other material contaminated with blood. Spread of disease by sexual intercourse is less likely. Period of communicability is from one or more weeks before onset of symptoms and may persist in most persons indefinitely.

Onset of the disease is usually insidious with anorexia, vague abdominal discomfort, nausea and vomiting; progression to jaundice is less frequent than with hepatitis B.

Although initial infection may be asymptomatic (more than 90% of cases) or mild, a high percentage of cases (50-80%) develop a chronic infection. About half of those chronically infected persons will eventually develop cirrhosis or cancer of the liver.

No longitudinal studies on the burden of hepatitis C infection in seafarers were identified.

A study published in 1992 conducted among a sample of 561 Spanish seafarers seeking attention prior to travelling abroad confirmed hepatitis C infection in 9% (52/561) of seafarers. Former intravenous drug use and tattooing were found to be independent risk factors for infection with hepatitis C. [25]

In a cross sectional study in the United States of Naval military recruits in 1989 the prevalence of hepatitis C virus was found to be 0.4% (9/2072). [15]

A Danish survey among 515 seafarers who sailed in international trade published in 1995 recorded a prevalence of 1.2% antibodies against hepatitis C.[38]

In Georgia, Hepatitis C virus infection is routinely assessed as part of the pre-employment exams. It was found that 11.5% (162) of a total of 1400 male Georgian seafarers were anti-HCV positive. Further studies indicated that 157 out of these 162 seafarers had active disease.[39]

Medical cards of 270 seamen in Croatia (less than 1% of all approx. 320 000 Croatian seamen) from one general practice in the area of Split were studied in the year 2006 for the presence of hepatitis C infection. Out of 37 test results 8 showed evidence of infection. Documented modes of transmission were intravenous drug use and blood transfusion.[40]

Denisenko collected data on Hepatitides among Russian seafarers from 2008 to 2010. Four out of 1630 seafarers were found to suffer from chronic hepatitis C.[41]

As with hepatitis B and HIV infection, the prevalence of hepatitis C infection in seafarers is driven by the local epidemiology of the disease. The data from Georgia are conflicting and need further studies.

ILO uses the same principles for hepatitis B and C infection to assess medical fitness in seafarers: With no signs (clinical and lab studies) of hepatic impairment and confirmed low level of infectivity the seafarers’ fitness is not restricted. [22] [23]

No vaccination against hepatitis C is available. Post exposure prophylaxis with IgG is not effective.  General control measures for hepatitis B also apply to hepatitis C.

Skin infection

Wounds are common in seafarers and they can easily become infected in the marine environment and present as impetigo, carbuncles, furuncles, cellulitis, otitis externa and skin abscesses. Dahl emphasizes that most wounds in seafarers must be considered contaminated, with antibiotic treatment started immediately in hand and puncture wounds and if cellulitis occurs. Pre-sea tetanus immunization is essential.[42]

Methicillin-resistant staphylococcus aureus

The occurrence of methicillin-resistant Staphylococcus aureus (MRSA) is a recognized cause of  nosocomial infection related to the use of antibiotics and poor hygiene practices. Clinical infection is associated with increased morbidity and mortality. Lately, the infection was reported as the cause of community acquired skin infections in individuals without established risk factors. The US Centers for Disease Control name the five C´s of MRSA transmission as follows: crowding, frequent skin-to-skin contact, compromised skin integrity, contaminated items and surfaces and lack of cleanliness.[43]

As ashore, MRSA is an emerging medical challenge on ships:

Outbreaks of community acquired MRSA are reported from day-care centres, military quarters, sport-teams and from ships. La Mar et al describe skin infections in two Navy soldiers; 125 mates from the same living quarters on board were examined with nasal swabs, of which 6.4% were asymptomatic MRSA carriers.[44]

Lucas et al. performed a chart review on all consultations to the telemedical advice service at George Washington University in the United States of America from the years 2002 to 2006.[45] Their analysis showed that 36% of skin infections in the year 2002 and 74% of skin infections in the year 2006 were clinically suspicious for infection with methicillin-resistant Staphylococcus aureus. They conclude that the number of skin infections reported to their service has increased during the study period and that the proportion of cases with features common to MRSA infection had doubled.  No studies are available on the prevalence of the infection and/or colonization in patients and staff of ship hospitals in passenger ships.

The relevance of global travel and transport as vectors of Methicillin-resistant Staphylococcus aureus strains has not been studied so far. In 1993 a tourist returning from travel and medical care in India introduced the resistant strain into British Columbia, Canada which spread to several hospitals and caused 12 cases of disease and 14 colonisations.[46] MRSA prevalence in resource-limited countries in Asia and Africa and in the seafarer´s population is ill-defined. 

The current evidence suggests that in relapsing or extensive skin infections in seafarers methicillin resistant staphylococcus aureus must be considered as a causative agent.

Microbiological resistance testing from wound material should be done whenever possible. In relapsing or extensive infections broad spectrum antibiotics covering MRSA may be justified. Transmission of MRSA among crew is possible. General hygiene measures and precautions in wound care (gloves, hand disinfection) apply.

Other skin infections

No further publications on seafarers were found concerning infections which are reported to occur in international short and long term travellers and immigrants, such as impetigo, scabies, pediculosis and infected insect bites, fungal infection or rare skin diseases like leprosy and cutaneus diphtheria. Despite the lack of published data to this topic, every practising port and ship physician is well aware of the relevance of fungal skin infections, that can easily be treated by hygiene measures and topical ointment: mainly tinea corporis (ring-worm), tinea pedis (athlete´s foot), tinea cruris (jock itch).