Crew or passengers aboard as well as contacts in ports who are incubating infections are common sources of respiratory infections for seafarers. Infective aerosols can also be sources.

A longitudinal study of the epidemiology of injuries and illnesses among passengers from medical log books on cruise ships revealed that respiratory tract infections were the most common cause of seeking medical attention by passengers and crew members aboard the ship.[70] Verbist reported that 12 % of attendances in a port clinic in Belgium can be attributed to respiratory diseases. The most frequent upper respiratory diseases were rhinitis, rhino-sinusitis and influenza, while lower respiratory infections, including exacerbations of chronic obstructive pulmonary disease were linked to cigarette smoking.[71] It is the practical experience of company, ship or port doctors that the crew members perceive the air-condition aboard as a cause of their frequent upper respiratory infections,

Schlaich et al. showed in a retrospective study based on medical log books from merchant ships under the German flag that respiratory infections are the most common causes of communicable diseases aboard cargo ships and may cause outbreaks of considerable morbidity. During more than 1.5 million person-days of observation, nearly one fourth of the visits to the ship’s infirmary were due to communicable diseases (45.8 consultations per 100 person-years). 33.9 crew members per 100 person-years sought medical attention for presumed acute respiratory infections. 68 outbreaks of communicable diseases were identified of which 66 were caused by acute respiratory infections and two by outbreaks of gastrointestinal infection.[8]

Legionellosis

Legionella species are known causes of travel related illness.[72] It is a waterborne disease, spread of disease is via inhalation of aerosols. In certain conditions potable water systems (showers), air conditioning, cooling towers, evaporative condensers, humidifiers, whirlpool spas, decorative fountains and respiratory therapy devices may harbour Legionellosis. No person-to-person spread occurs.

It is an acute bacterial disease with two distinct clinical manifestations: Legionnaires disease (incubation period 2-10 days) and Pontiac fever (5-72 hours). Both conditions present with anorexia, malaise, myalgia, headache and fever. Abdominal pain and diarrhoea are frequent. Legionnaires disease is a common cause of pneumonia and is characterized by non-productive cough. Chest radiographs are variable and may show patchy, bilateral or focal areas of consolidation. The fatality rate remains at 15%. Pontiac fever is a self-limiting febrile illness that does not progress to pneumonia or death.

In a study on Legionellosis associated with ships from 1977 and 1997, being on board a ship was an established a risk factor for an infection with Legionella spp. Cases were found to be less common among crewmembers than among passengers.[73] Poorly constructed or maintained water or air management systems involving the water supply, swimming pools and beauty areas are the sources of infection. Using the whirlpool spa on a cruise ship has been identified as a risk factor for passengers.[74]

A case study from a cargo ship described two lethal cases of Legionellosis in two mechanics working with the pump of the ship´s contaminated water system on a ship under repair in the port of Barcelona.[75]

A prevalence study was carried out on 7 ferries and 2 cruise ships docked in Sardinia, Italy in 2004. Water samples from critical sites were analyzed for the presence of Legionella spp. Legionella spp. was identified in samples of 6 out of 7 ferries.[76] A prevalence study of 276 water samples from 10 cruise ships and 21 ferries showed heavy colonization of water distribution systems on ferries (38% of hot water and 18% of cold water systems).[77]

Generally, ships have been recognized as an at risk environment for Legionella colonization in the drinking water installation due to poor temperature control and other factors. Proper maintenance and construction are of major importance for Legionella prevention. WHO recommends regular sampling procedures.[47]

If a case of Legionnaires disease in a sailor is confirmed, potable water sampling on the ship and assessment of the condition of the system are mandatory.  Legionellosis is a notifiable disease in most countries. A cluster of diseases warrants an epidemiological investigation with environmental sampling and active surveillance of contacts by public health authorities.

Tuberculosis

Tuberculosis is an infectious disease which damages one or more organs through a slowly multiplying bacterium. Infections of tuberculosis are acquired from human aerosol or droplets which the infected patient spreads while coughing and breathing.

Tuberculosis can express many different symptoms, which initially may not be very distinctive. Infection of the lung is the most frequent form and also the most important because of its potential for transmission of the disease (so- called “smear-positive Tuberculosis”). Pulmonary tuberculosis commonly presents with symptoms like cough, expectoration, feeling ill, and a slight temperature rise. Due to the insidious symptoms, the diagnosis of tuberculosis often is delayed. Therefore, contact between the patients and their families or other crew members are possible before a contagious patient is being diagnosed, isolated and treated.

Assuming lifelong infection, about one-third of humanity is infected with Mycobacterium tuberculosis. It occurs globally but is a major cause of death and disability in developing countries where the disease is closely linked to the HIV epidemic. The densely populated countries of Asia harbour the largest number of cases, many of them being major suppliers of seafarers to international trade: India, China, Indonesia, Bangladesh and Pakistan together accounted for about half of the world´s new TB cases in the last decade. While most of the burden of the disease is carried predominantly by Asian countries, it is sub-Saharan Africa and the former Soviet Union that showed the most striking increase in case load during the 1990´s.[78] The resurgence of multidrug and extensively drug resistant tuberculosis in Eastern Europe, Asia and Southern Africa is of special concern.

Notwithstanding the enormous global burden of disease, the interaction between M. tuberculosis and humans is relatively benign. As a rule of thumb, untreated sputum smear-positive cases infect 5-10 other individual cases each year. In immunocompetent humans, as most seafarers are, only about 5% of infected individuals develop progressive primary disease following infection. Also, the progression time is slow, averaging 3-4 years. After 5 years, there is a low annual risk of developing tuberculosis by reactivation of the infection, which is then said to be latent. On the other hand tuberculosis has a high case-fatality rate among untreated or improperly treated cases. About 2/3 of untreated smear-positive cases will die within 5 to 8 years.[76]

Systematic data on the prevalence of infection, occupational disease transmission and the occurrence of clinical disease in the population of seafarers is very limited.

On a United States Navy amphibious assault ship,one person had cavitating tuberculosis in 1998 which resulted in extensive transmission. Of 3338 crew who were subsequently skin tested, 21% (n=712) had new latent infection and n=21 were found to have active tuberculosis.[44]

A longitudinal study on tuberculin skin rates in over one million US Navy and Marine Corps personnel in the United States from 1999 to 2002 showed higher annual conversion rates in personnel of amphibious ships (1.76%) as compared to aircraft carriers (Relative Risk 3.33 95% CI 2.98-3.71).[79]

A surveillance programme has been in operation since 1992 for USA Seafarers` International Union members. This used tuberculin skin testing and showed a reduction in positive results from ca 15% in 1994 to ca. 4% in 1998. A higher prevalence rate was found in submarines and those working on cruise ships.[80]

A systematic review of 78 seafarers referred to the Naval Hospital in Shanghai, China in 1990 found the majority of clinical symptoms in seafarers diagnosed with active TB to be cough and expectorations (71%) and haemoptysis (51%). Only 6 of the cases diagnosed with tuberculosis were smear-positive.[81]

One retrospective longitudinal study from Denmark on the risk of tuberculosis in seafarers compared to the general Danish population was identified. Hansen et al. linked a national registry containing all reported cases of tuberculosis in Denmark with a research register on all seafarers on Danish ships. The study period was 1992 to 2003. All strains of tuberculosis were analysed using DNA subtyping. The risk of tuberculosis among male seafarers was 1.51 (1.10-2.01) compared with the general population. Only 7 out of 64 cases of tuberculosis were assessed to be likely or possibly shipping-related. The authors conclude that despite multi-cultural crews aboard, including many from high incidence countries, only limited transmission of Mycobacterium tuberculosis takes places among crew aboard or during shore leaves.[82]

The same authors showed in an earlier longitudinal study from the same database in Denmark that the Standardized Incidence Ratio (SIR) of tuberculosis among male seafarers between 1990 to 1993 was not increased as compared to the general population.[26]

A case report of cavitating smear and culture positive tuberculosis in a 32 years old sailor from the Philippines aboard a United States aircraft carrier described the outcome of this incident in the year 2006. The patient and other air-wing sailors slept in an open-bay compartment with 120 bunks arranged in stacks of three; another compartment of the same size was adjacent and connected to the patient´s compartment. The ship sailed with over 5000 soldiers aboard. Despite several months of potential exposure in a high-risk setting as described above, results from screening of all sailors suggested limited transmission of Mycobacterium tuberculosis on the ship.  No secondary cases were identified. 13% of close contacts had latent tuberculosis. The authors concluded that tuberculosis transmission was minimal despite the sleeping arrangement.[83]

These publications demonstrate the complexity of risk assessment for tuberculosis in seafarers. Individual risk factors leading to infection, and for progression, recurrence and adverse outcome of disease are: HIV infection, alcoholism, smoking, malnutrition, country of origin, social status and non-adherence to treatment. The living and working conditions in the country of origin and on the vessel (intimacy and duration of possible contacts, the ventilation in the shared environment) and the degree of contagiousness of the index case (smear-positive or negative, cavitating pulmonary lesion, multidrug-resistant TB etc.) must be considered.

Commonly, if a case of tuberculosis is detected among crew, the seafarer will be hospitalized as soon as possible and repatriated as soon as he is not infectious any more. If it is decided that the seafarer is to continue to travel on the ship, he must be isolated in his cabin if smear-positive or unknown. Infectivity is usually best controlled through prompt specific therapy, normally leading to disappearance of viable organisms in the sputum in 2-4 weeks and full clearance in 4-8 weeks.[84] The disease and the therapy cause a major reduction of the patient’s physical fitness and working ability. Furthermore, adverse reactions from the drugs like liver dysfunction must be checked for, with examinations every other week. Even a rapid recovery from the disease leads to a period of limited ability to work for at least 4-5 months. Before getting back to work on board, the X-ray of the lung should show obliteration of any pulmonary cavities and a significant reduction in the inflammatory changes.

While there are detailed recommendations of World Health Organization and the European Centers for Disease Control concerning risks of infection and contact tracing if disease has occurred on board for international air travel, no such recommendations exist for the ship travel. It is common practice that in the ship’s environment all crew members on cargo ships are to be classified as “close household” contacts and be followed up for infection and disease. In passenger ships this is a decision to be made by individual assessment of the living and work-place condition. It is usually admitted that a stay exceeding 8 hours in a restricted area like a domestic room should be classified as a “close contacts”. Furthermore, close contact should be considered after direct contact with respiratory, oral, or nasal secretions from a symptomatic case of smear positive pulmonary / laryngeal tuberculosis (e.g. an explosive cough or sneeze in the face, sharing of food, sharing eating utensils during a meal, kissing, mouth-to-mouth resuscitation or performing a full medical exam including examination of the nose and throat).

Management of potentially exposed contacts to a source of tuberculosis infection (contact tracing in seafarers):

1. For some years a special blood test, the interferon gamma release assay (IGRA), has been used to discriminate between an acute infection with mycobacterium tuberculosis and a vaccination-induced immune reaction. This method seems to be the most practicable for use in the maritime environment where passengers and crew may not reside at the place of investigation. The test should be performed not earlier than 8 weeks after exposure has ended because the organism needs this time to induce the specific lymphocytes that are measured. The cost of the test is slightly higher than the skin-test but it’s more practical and more specific. Local health authorities may initiate the tests in cooperation with the shipping company.

2. An X-ray on persons with a positive blood test will demonstrate any manifestations of pulmonary tuberculosis. A combination of a positive IGRA test and a negative X-ray indicates latent infection. But always consider extrapulmonary tuberculosis if cervical or axillary lymph nodes, pleural or pericardial effusion, ascites or abdominal para-aortic lymph nodes are detected. In latent tuberculosis, preventative treatment with Isoniazid for nine months may prohibit a later recurrence of the infection. Decision making for preventative treatment should involve a medical specialist to assess comorbidities and strict cehcks for possible contraindications, such as preexisting liver dysfunction.

3. The diagnostic skin-test is an alternative to IGRA to see whether the tested patient’s immune system has responded to the tuberculosis bacterium. Like the IGRA a time gap between exposure and a positive test result exists. This test cannot discriminate between a latent infection and a manifest affection. Hence, for persons who test positive, an additional X-ray is necessary. In immunosuppressed persons further tests to rule out extra-pulmonary diseases are warranted. Furthermore, the test cannot discriminate between an acute infection and an immune reaction from an earlier vaccination. Moreover, the skin test reaction has to be examined by a physician two days after the solution was injected. This may be a problem for seamen on ships with short port-calls. Overall, if available, the IGRA is the preferred screening method for the shipping industry.

An X-ray of the lung shows only well-developed pulmonary disease, latent infections cannot be identified. Using only this method without IGRA or a skin test, a second X-ray is necessary about two months after contact with the index patient, because of a delayed expression of the infection. X-ray is obligatory in symptomatic persons after contact with tuberculosis. Symptoms could be cough and expectoration, malaise or loss of body weight.

Overall, if screening of close contacts to a smear positive case of tuberculosis on a ship results in positive tuberculin skin or IGRA tests, the individual should be referred to a medical specialist with experience in global tuberculosis epidemiology and care. Seafarers should receive written information from the company or public health authority on the time and duration of contact to a tuberculosis index case and recommendations for follow up in their home country if their contract ends before testing was possible.

Human Influenza

Influenza is an acute respiratory infection that rapidly spreads around the world in seasonal epidemics. It occurs in small outbreaks or epidemics. In annual influenza epidemics, 5-15% of the general population are affected with upper respiratory infections. Morbidity and mortality is highest in certain risk-groups, e.g. children, pregnant women, the elderly, chronically ill persons. The disease is spread from person to person through the air. Influenza is very contagious especially in crowded environments with close interpersonal contacts, like ships . Here, the clinical attack rates can reach to more than 50%. The incubation period averages 2 days (range 1-4), in adults, viral shedding and probable communicability is greatest in the first 3-5 days of illness. In young children and the immuno-compromised, virus shedding can occur for longer (up to 10 days).[82]

There have been well documented outbreaks of influenza A and B on passenger and naval ships, mainly from the northern hemisphere. Several detailed outbreak studies have been performed. Attack rates among crew members were described to be between 0% and 42% for influenza-like illness and 1% and 13% for acute respiratory infections. For passengers attack rates for influenza-like illness were between 1% and 37% and for acute respiratory infection between 2% and 18%.[85-89]  In one United States Navy ship the attack rate of influenza-like illness was found to be 42% despite an influenza vaccination rate of 95% before the outbreak.[86] The particular vulnerabilities of cruise ships to influenza include 1) large numbers of persons in semi-closed environment, 2) the short incubation time of influenza, 3) mixing of passenger and crew from northern and southern hemispheres, 4) high numbers of persons at risk for morbidity (elderly, pregnant women, children).[90]

Though comparability of attack rates between studies is limited by different methods of case finding, definition and control measures, rates in crew and passengers were within the same range.  Overall, influenza outbreaks among crew members and passengers on all types of ships pose a travel related risks for exposure to influenza viruses even if the vessel is in regions where influenza is not in seasonal circulation.

Due to highly publicized outbreaks on cruise ships and corporate and global planning for pandemic influenza, extensive recommendations by the World Health Organization, the Centers for Disease Control and the EU Project ShipSan Manual are available for prevention, surveillance and control of seasonal and pandemic influenza on board of cargo and cruise ships.[91] [92] Control measures during a recognized outbreak include clinical and virological surveillance, antiviral therapy with Rimantidin or Oseltamivir and post-exposure vaccination. Since influenza infections may be introduced to cruise ships by passengers or crew it is recommended that cruise lines should attempt to achieve at least an 80% vaccination rate among crew members among each ship each year.[95] Travellers at high risk for complications who have not been vaccinated against influenza during the preceding fall or winter season should consider receiving influenza vaccine before travel.

Key elements for the prevention and control of Influenza outbreaks on cruise ships and large vessels with many crew members include 1) active and / or passive surveillance using standard case definitions, 2) use of targeted rapid influenza testing and viral cultures to confirm cases of influenza virus infection, 3) isolation of all crew members meeting the influenza-like illness case definition, 4) use of antiviral agents for treatment and, if indicated for prophylaxis, 5) monitoring of intervention results.[93]

Pandemic Influenza - Novel Influenza A H1N1

Global spread, high attack rates and high excess mortality characterize pandemic influenza. Occurrence of pandemic influenza is unpredictable and believed to arise when a genetically re-assorted virus reaches susceptible populations. The occurrence of pandemic influenza requires special considerations by ship owners and masters, such as active and passive surveillance, information flow between company and vessels, isolation facilities on board, vaccination of crew and passengers, antiviral agents for prophylaxis and treatment and personal protective equipment.[83] [94]

The 2009/2010 pandemic caused by Novel Influenza A H1N1 has resulted in detailed recommendations to the shipping industry by the World Health Organization, the International Maritime Health Association and the EU ShipSan project.[95] Several outbreaks of Influenza A H1N1 on passenger ships were reported in the press but assessments of the burden of disease in seafarers or formal outbreak investigations were not published.  The World Health Organization published a global study on infection control measures on ships and in ports. Of 31 companies that operated 960 ships, 32% experienced health screening measures by port health authorities. Twenty-six percent of ports performed embarkation screening and 77% of shipping companies changed procedures during the early stage of the pandemic. Four companies reported outbreaks of pandemic influenza A (H1N1) 2009 on ships, which were ultimately stopped through infection control practices. Public health measures did not interfere substantially with port and ship operations with the exception that some port authorities delayed embarking and disembarking procedures. However, in shipping companies’ experience, measures were inconsistent between port health authorities. Antiviral drugs and pandemic vaccine was not made available.[96]The USA cruise ship industry cooperated early in the pandemic, in accordance with Centers of Disease Control procedures. Their experience reinforced the importance of pandemic planning for governmental agencies and private industries alike, including the development of practical procedures in advance.[97]

SARS (Severe Acute Respiratory Syndrome)

The disease is caused by a coronavirus and transmitted by person-to-person spread. It caused a febrile, flu-like illness. Complications included pneumonia and respiratory failure. The disease had emerged in 2003 and caused a pandemic. Global spread of the disease by travellers is well documented and resulted in the revised WHO International Health Regulations 2007 that apply to all vessels and ports  involved in international travel.[98] They are highly relevant to the international shipping industry.  SARS occurred on aircraft in several occasion, however no cases have been reported on ships, in either crew nor passengers. Globally the last case of the disease occurred in 2004 in China.[99] No specific antiviral treatment or vaccine is available. If the disease reoccurs, outbreak control will have to rely on early detection, medical treatment and isolation of infected patients and use of personal protective equipment.  Good risk assessment and communication are the key to public health control in populations on board ships.[88]  While SARS has not been detected since 2004, another coronavirus emerged in 2012: Middle East Respiratory Syndrome, Coronavirus, or MERS-CoV, which shows the same pattern of transmission, however it has a higher mortality rate.

Avian Influenza (Influenza H5N1, “Bird Flu”)

The highly pathogenic avian influenza A (H5N1) causes epizootic animal outbreaks in Asia, Europe, the Near East, and Africa . So far, the spread of H5N1 virus from person-to-person has been very rare, limited and unsustained. No infections in association with seafaring have been reported. No risk factors for transmission on board passenger or merchant ships can be identified.

Chickenpox and shingles (Varicella-zoster virus)

The varicella-zoster virus causes both chickenpox (varicella) and shingles (herpes zoster). The latter is usually a disease found in the elderly. Chickenpox is a highly contagious illness with a characteristic rash transmitted by the airborne or droplet pathway and by person-to-person contact, with a usually incubation period of 14 (10-21) days. Secondary attack rates reach close to 90% in susceptible household contacts. While it is a usually a mild disease in healthy children, serious complications may arise in adults, those who are immunocompromised, pregnant women and infants.

Varicella zoster virus predominantly affects children in temperate countries, with near-universal seroconversion occurring by late childhood. However, the epidemiology is changing where vaccination has been introduced as a routine immunization, in countries such as Germany, United States, Uruguay, Quatar, Australia, Canada and South Korea. The epidemiology of chickenpox is even more complex in tropical and subtropical regions where seroconversion generally occurs in late adolescents and adults and may be less likely in rural areas than in urban areas. [82]

A cross- sectional serosurvey in 1533 US Navy and Marine Corps recruits was conducted in June 1989. Seronegativity was 6.7% for varicella. [100]

In May 2008 the European Centres for Disease Control published a risk assessment when varicella transmission among crew members of a large Italian cruise ship was recognized.

A total of eleven crew members were reported sick. No cases occurred in the passengers.[101]

Between November 2007 and April 2008 five cases of chickenpox in four vessels were reported to the Hamburg Port Health Center from two passenger and two cargo ships. Cases originated from Indonesia (1), Philippines (2) and Sri Lanka (2). The majority of passengers were UK residents. Sources of infection were other crew members, passengers and persons in the home countries.[102]

Idnani studied seroprevalence of Varicella immunity in Indian cruise ship employees. He found 17% of 121 Indian seafarers during pre-employment exams to be IgG negative. [103]

Acevedo et al presented data on three outbreaks of varicella of Royal Caribbean Cruises Ltd. In 2009 three cruise ships of the company were affected and in 2010 5 ships (69 crew, 29 passengers). Crew members from 26 nations were involved, a total of 2085 contacts were vaccinated.[104]

A large part of the work force on ships originates from (South-East) Asia and Eastern European countries. Port health doctors, ship doctors and shipping companies need to be aware that a substantial portion of their employees from Asia and Africa may be non-immune to varicella-zoster virus. Non-immune employees may introduce the disease from their home countries to the ship if they start a new contract within the incubation period and are at risk to be infected by children or other crew-members on board ships. It has been suggested that pre-employment serological screening and –if necessary vaccination- may be cost-effective as compared to the consequences of an outbreak at sea. [95] Certainly this is a serious consideration for crews on large passenger ships with children, immunosuppressed persons and pregnant women aboard.

If an outbreak at sea occurs the following measures are recommended:

-        isolation of the sick person in cabin until scabs resolve

-        person-to-person contact of the sick only with immune crew members

-        inform crew and passengers and alert them on typical symptoms, such as rash and fever to assist passive case-finding.

-        If appropriate, provide post-exposure vaccination within 72 hours

 -       On cruise ships, inform special risk groups (pregnant women)-

-        Notification of port health authorities

Oral aciclovir can reduce the duration of contagiousness and complications. Varicella vaccine is effective both for primary prevention and immediate post-exposure prophylaxis. Varizella zoster immunoglobulin is indicated only if there is high risk of complications, as in pregnant women and immunosuppressed persons.

Rubella (German measles)

Rubella virus circulates worldwide in susceptible humans. Spread is via droplets or direct contact with infected persons.  Incubation period is from 14-17 days. Immunity is usually permanent after natural infection and probably life-long after immunization.

Risks of infection include non-compliance with childhood vaccination programs, contact with a case, crowded working and living conditions. Clinically, rubella is indistinguishable from febrile illness with rashes due to measles, dengue, parvovirus B 19, Herpesvirus 6, Coxsackie virus, Echovirus, Adenovirus or scarlet fever. Adults may experience a 1-5 day prodrome of low-grade fever, headache, malaise, mild coryza and conjunctivitis. Post-auricular, occipital and posterior cervical lymphadenopathy is the most characteristic clinical feature and precedes the rash by 1-5 days. Laboratory diagnosis of rubella is required since clinical diagnosis is often inaccurate.

Rubella transmission was reported among crew members of two different commercial cruise ships from Florida in the year 1997. In one ship 7 out of 900 crew members and 2000 passengers had disease consistent with acute rubella infection. Most of the crew members were born outside the United States and had no documented immunity. In a second cruise ship with 345 crew and 8400 passengers a cluster of illness with a rash among crew was notified to the Centers of Disease Control. A serosurvey confirmed Rubella in 16 (4%) of crew members an additional 25 (7%) had no immunity.[105] In both cruises crew members represented 50 different countries. No passengers were infected with rubella during that outbreak, but 1% of approx. 3500 passengers surveyed were pregnant women

An outbreak of rubella was investigated aboard a ship of the German Navy in 1996. 20 cases out of 330 crew members over a period of 9 weeks were detected. The attack rate was 57% in non-vaccinated personnel.[106]

Though Rubella infection in adult seafarers is a rare event, it must be included in the differential diagnosis of a febrile rash illness. Laboratory diagnosis must be used if in doubt.  

Measles

Spread of Measles is airborne or via droplets. It is highly communicable, with primary attack rates in susceptible individuals exceed 90%. The viral disease is clinically identified by the typical symptoms of prodromal fever, conjunctivitis, coryza, cough, and small spots with white or bluish-white centres with a erythematous base on the buccal mucosa (Koplic spots). A characteristic red blotchy rash appears on the third to the seventh day, the rash begins on the face, then becomes generalized, lasts 4-7 days, and sometimes develops with brown desquamations. Incubation period is about 10 days, but may be 7 to 18 days from exposure to onset of fever, and usually 14 days until the rash appears. The period of communicability is from 1 day before the beginning of the prodromal period (usually 4 days before rash appears) to four days after rash appearance.

Factors facilitating outbreaks are low immunization rates in seafarers or passengers.

A cross- sectional serosurvey in 1533 US Navy and Marine Corps recruits was conducted in June 1989. Seronegativity was 17.8% for measles.[98] No reports of cases of measles in seafarers were identified.

If the disease is clinically suspected in a seafarer or passenger, laboratory confirmation is necessary. The detection of measles-specific IgM antibodies, present 3-4 days after rash onset, or a significant rise in antibody concentration between acute and convalescent sera, confirms the diagnosis. If available, virus isolation from nasopharyngeal swabs collected before day 4 of the rash or from urine before day 8 of the rash is helpful to ascertain the diagnosis.

If a case of measles is suspected or confirmed on a vessel, isolation measures, immunization of non-immune contacts up to 72 hours after contact is necessary. Contraindications for the administration of a live vaccine must be observed. Immunoglobuline are to be considered in persons with high risk of complications (contacts under 1 year of age, pregnant women or immunocompromised) or where the vaccine is contraindicated. Notification of public health authorities is mandatory to prevent the international spread of the disease.

All susceptible travellers and seafarers must be vaccinated before they start their travel, in accord with national recommendations.

Mumps

Spread of Mumps is airborne, via droplets or by contact with saliva. The incubation period is about 16 to 18 days. It is an acute viral disease characterized by fever, swelling and tenderness of one or more salivary glands –usually the parotid and sometimes the sublingual or submaxillary glands.  Orchitis, most commonly unilateral, occurs in 20-30% of male cases. As many as 40-50% of mumps infections are associated with respiratory symptoms, aseptic meningitis occurs in up to 10%. Usually patients recover without complications, though many require hospitalization. Immunity is generally lifelong. Most countries have now introduced mumps in their childhood vaccination program. In countries were mumps vaccine has not been introduced, the incidence of mumps remains high, mostly affecting children under 5 years.[64]

A cross- sectional serosurvey in 1533 US Navy and Marine Corps recruits was conducted in June 1989. Seronegativity was 12.3% for mumps.[98] No clinical cases of mumps in seafarers were reported in the literature.

Though underreporting may be possible, mumps is seemingly not occurring in seafarers on a significant scale. Most seafarers some from countries were mumps vaccine is part of the childhood immunization schedule. If the disease is suspected it can be confirmed by serological test and detection of virus by reverse transcription polymerase chain reaction (RT-PCR) from appropriate clinical specimen (throat swab, urine, cerebrospinal fluid). As a control measure, respiratory isolation for five days from onset of parotitis is recommended.

Corynebacterium diphteriae and Bordetella pertussis

Both infections are transmitted by direct contact with carriers or a case of disease. No reports on diphtheria in seafarers were identified. Canals et al. questioned 505 seafarers during their pre-medical examination in Tarragona Spain and found that only 6.1% of seafarers were properly vaccinated against tetanus and diphtheria.[107] One case of diphtheria was diagnosed in a 72 year old female British passenger who developed a sore throat during a cruise in the Baltic Sea.[108]

Meningococcal Meningitis

Neisseria meningitits, Streptococcus pneumonia and Haemophilus influenza type b (HIB) cause more than 2/3 of all meningitis infections in adults. Meningococcal meningitis is unique among the major causes of bacterial meningitis in that it is both an endemic disease and also causes large epidemics. It is a severe disease with high case fatality rate: 8-15%.[85]

Meningococcal Meningitis is characterized by a sudden onset of fever, intense headache, nausea and often vomiting, stiff neck and photophobia. A petechial rash may occur. Meningococcal sepsis is the most severe form of infection with petechial rash, hypotension, disseminated intravascular coagulation and multi-organ failure.

Transmission is via direct person-to-person contact, including respiratory droplets from the nose and throat of infected people. The incubation period is 2 to 10 days.

One case of a suspected meningococcal infection in a 24 year old sailor was reported in 2003 from a United States navy aircraft carrier. Chemoprophylaxis was given to 99 close contacts, no further cases occurred.[109]

While meningitis on ships is rare, it may be a catastrophic event if a case is suspected in a sailor. It is a severe, life-threatening disease. Patients may rapidly deteriorate. If suspected on board, immediate antibiotic treatment, isolation measures and possibly chemoprophylaxis to all members of the crew are necessary steps. Close collaboration with the telemedical service is necessary. If confirmed, public health authorities must be notified.

The other significant point for the shipping industry concerns vaccination requirements. Although the disease is not covered by International Health Regulations, some countries may require a valid certificate of immunization against meningococcal meningitis as a condition of entry, e.g. Saudi Arabia. Further information can be found at www.who.int/topics/meningitis/en/.

Vaccines containing groups A, C, Y and W-135 meningococcal polysaccharides are available. The vaccines are effective for prevention. Sailors in global shipping are at risk groups due to their travel activity, living and working conditions on board and the limited access to medical and diagnostic care during their travel.

Streptococcal Diseases

β- haemolytic Streptococcus  pyogenes (Group A streptococcus) infections cause a variety of diseases, the most frequently encountered conditions are invasive respiratory infections such as streptococcal pharyngitis/ tonsillitis (sore throat), pneumonia and otitis media and skin infections such as impetigo, pyoderma, or cellulitis.

Other conditions that arise from β-haemolytic streptococcal Group A infections that will not be discussed here are toxic syndromes (scarlet fever and streptococcal toxic shock syndromes) and post-infective conditions (rheumatic fever, glomerulonephritis and Sydenham´s chorea). Also, other groups of streptococci (β- haemolytic Streptococcus  pyogenes groups B-G and α-haemolysing groups) are not included in this review since they are of limited clinical relevance to seafaring (e.g. diseases of newborns, women, in pre-existing conditions such as valvular heart disease, dental caries of early childhood or asymptomatic colonization).

Streptococcal Sore Throat 

A sore throat is a common disease in both, the general population and in seafarers.[8] It is an inflammation of the throat (pharyngitis), resulting in pain on swallowing. It is transmitted by respiratory droplets or direct contact. Explosive outbreaks of streptococcal infection may follow ingestions of contaminated food. Milk and milk products, egg salad and similar preparations have been associated most frequently with food borne outbreaks. Incubation period is short, usually 1-3 days.

Most cases are due to respiratory viral infections (rhinovirus, coronavirus, adenovirus, influenzy virus, parainfluenza virus, respiratory syncytial virus), Epstein-Barr virus or coxsackievirus. Viral pharyngitis is a self-limiting condition that does not usually require a specific diagnosis and treatment.

Bacterial pharyngitis is less common. It´s single most frequent cause is Streptococcus pyogenes (Group A streptococcus). It is the cause of a sore throat in 10-15%. Other rare bacterial causes include Neisseria gonorrhoea, C. diphteriae or Mycoplasma pneumonia.

Patients with streptococcal sore throat typically exhibit sudden onset of fever, exsudative tonsillitis or pharyngitis (sore throat) and tender, enlarged anterior lymphnodes. Coincident or subsequent otitis media or peritonsillar abscess may occur. Possible non-suppurative complications include acute rheumatic fever and glomerulonephritis.

There are clinical scores available to differentiate between viral and bacterial sore throat infection. Also a rapid antigen detection test is used in outpatient settings of many countries to guide on the use of antibiotics.

The WHO International Medical Guide for Ships recommends using antibiotics in person with sore throat when three or more of the following symptoms are present:

-yellowish creamy material on the tonsil or back side of the throat

-tender, enlarged lymph nodes below the jaw

-fever

-cough

It is well recognized that the risk for spread of infection is increased in crowded living situations due to respiratory transmission and outbreaks from contaminated food. Epidemic infections with respiratory agents causing sore throat have been documented from settings with confined spaces such as military barracks or college dormitories.

No systematic studies to identify the risk and causes (by throat swabs and microbiological identification) of sore throat on ships were identified in the published literature. Also there are no reports on outbreak investigation on ships that included microbiological identification of causative agents.

One survey published from the Russian Federation investigated epidemic outbreaks of tonsillitis in 6 state fishery ships. The authors found that outbreaks of tonsillitis occurred in ships with more than 350 crew members. However the study did not include microbiological identification of causative agents.[110]

A case report describes four cases of myocarditis including three fatalities caused by Coxsackie virus – a rare cause of sore throat- in a group of 18 stowaways who travelled in a shipboard cargo container. No fatalities were reported in the crew.[111] However no conclusions on the risk of viral sore throat in seafaring can be drawn from this report.

In summary, due to the lack of specific data from the shipping environment, epidemiological data from the general population must be applied. Of note there are well recognized geographical differences on the frequency of pharyngitis/tonsillitis: The syndrome is more frequent in temperate than in tropical environments.

A pragmatic approach to the use of antibiotics in the shipping environment is the above described practice guidelines as given by the WHO Medical Guide of Ships. With this approach, antibiotic treatment will probably be initiated more frequently than in the outpatient setting ashore. This seems well justified to avoid invasive or toxic consequences that cannot be easily identified or treated during travel. Also, early antibiotic treatment will lower the risk of person-person transmission of bacterial disease on board.

Beyond early treatment WHO does not recommend to isolate persons with sore throat in the shipping environment.

Explosive outbreaks of sore throats on ships must raise a high suspicion of contaminated food (milk, milk-products and eggs). People with skin lesion must be excluded from food handling. Carrying a rapid antigen detection test on board of passenger ships is well justified to adequately handle sore throat outbreaks in passengers and crew.