Travel medicine

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chapter 45 Travel medicine

INTRODUCTION AND OVERVIEW

There has been an increasing trend for people to travel internationally.¹ Ease of air transportation has ensured that nearly 1 billion people travel internationally each year to every part of the globe.² These travellers are potentially exposed to infectious diseases for which they have no immunity, as well as other serious threats to wellbeing, such as accidents and exacerbation of pre-existing medical and dental conditions. Conservatively, it is estimated that 30–50% of travellers become ill or are injured while travelling.^3,⁴ Relative estimated monthly incidence rates of various health problems have been compiled elsewhere.³ The risk of severe injury is thought to be greater for people when travelling abroad.^1,⁵

In terms of morbidity, infectious diseases such as respiratory tract infection and traveller’s diarrhoea, and injuries, are important concerns for travellers.^1,^4,⁵ The main health complaints of returned travellers vary considerably, depending on the country visited and the duration of the visit. Some studies have reported, based on travel insurance claims, that respiratory, musculoskeletal, gastrointestinal, ear, nose and throat, and dental conditions were the most common presenting problems,⁶ whereas others have found that infectious disease (43.5%), accidents involving the extremities (15.3%), psychiatric conditions (8.2%), pulmonary disorders (4.7%) and accidents involving the head (4.7%) were the most common.^3,⁷ Fortunately, few travellers die abroad, and those who do tend to die of pre-existing conditions, such as myocardial infarction in travellers with known ischaemic heart disease. However, accidents are also a major cause of travel-related mortality.⁸ This chapter highlights some of the current issues in travel medicine, but excludes specific discussion concerning migrant health.

DEFINING TRAVEL MEDICINE

Travel medicine is a new multidisciplinary specialty area that has emerged in response to the growing needs of the travelling population worldwide. Nearly all general practitioners (GPs) will need a basic knowledge of travel medicine, some GPs will make it an area of special interest and there are medical specialists whose whole practice is travel medicine.

Travel medicine seeks to prevent illnesses and injuries occurring to travellers going abroad and manages problems arising in travellers coming back or coming from abroad. It is also concerned about the impact of tourism on health and advocates for improved health and safety services for tourists.^9a

The latter aspect recognises the impact of travel on ecosystems around the world, particularly the introduction and spread of diseases and disease resistance.

The roles of the GP or travel health adviser in the provision of travel health advice can be regarded as a continuum (Fig 45.1) and include:

• providing pre-travel assessment and advice, which may take place in a travel medicine clinic, during a standard general practice consultation, or through giving advice to other practitioners

• advising on other precautions that should be taken against diseases to which the person is likely to be exposed during travel

• immunising travellers for their protection

• immunising travellers to provide the relevant certificates to facilitate travel through epidemiological control posts at sea and air ports

• prescribing appropriate prophylactic and self-treatment medications

• advising on important safety nets for travellers abroad, including travel insurance and finding medical assistance abroad

• advising on follow-up of travellers returning from overseas

• managing medical problems of travellers from abroad, which may also involve aeromedical evacuation, emergency assistance and even ‘good Samaritan’ acts on board aircraft or abroad

• providing advice on health, including pre-existing problems while away

• informing public health authorities about travellers presenting with any possible notifiable disease.

FIGURE 45.1 Relationships in the continuum of travel medicine

PRE-TRAVEL HEALTH CONSULTATION

The pre-travel health consultation involves consideration of and advice about various aspects of travel-related health, including fitness to travel and the health risks of travelling in itself, including exposure to infectious diseases and diseases arising from travel. This may necessitate the provision of malaria and other chemoprophylaxis, and various vaccinations. The areas that may be covered in the pre-travel health consultation with travellers are listed in Table 45.1.

TABLE 45.1 Areas that might be covered in pre-travel preparation of patients going aboard

Advise/discuss
Insects	Repellents, nets, permethrin
Ingestions	Care with food and water
Infections	Skin, environment
Indiscretions	STIs, HIV
Injuries	Accident avoidance, safety
Immersion	Schistosomiasis
Insurance	Health and travel insurance
	Finding medical assistance abroad
	First aid advice
Vaccinate
Always	National immunisation schedule vaccines
Often	Hepatitis A, influenza
Sometimes	Typhoid
	Japanese encephalitis
	Meningococcal disease
	Polio
	Rabies
	Tetanus–diphtheria
	Yellow fever
Older travellers	Pneumococcus
	Influenza
	Pandemic influenza, e.g. pandemic (H1N1) 2009
Prescribe
Always	Regular medication
Sometimes	Antimalarial medication
	Diarrhoeal self-treatment
	Condoms
	Traveller’s medical kit

Source: modified from Seelan & Leggat 2003¹⁰ and Ingram & Ellis-Pegler 1996¹¹

Before the pre-travel consultation, a risk assessment needs to be undertaken, evaluating the risks of both the destination and the individual travelling there. Information on the exact itinerary and special medical problems of the traveller needs to be obtained early, up to 6–8 weeks before travel for most travellers, perhaps longer when travellers are going overseas for long-term employment, placement or holiday touring. In the clinic setting, it is preferable that this information is obtained well before the traveller presents for their first face-to-face consultation. It is necessary to establish:

• where they are travelling

• which areas of those countries they plan to go to

• what they plan to do in that country

• how they are going to get there

• at what time of year they are departing

• how long they will be travelling for.

This information may be obtained by a standardised questionnaire, which may be developed in the context of a travel clinic network or general practice network, or by individual travel health advisers. The World Health Organization (WHO) has provided an example of the types of questions to be asked in international travel and health.¹² Practice or clinic staff can assist by ensuring that this information is obtained before the formal consultation. It is important that the procedure is time efficient for a practice, to improve flow and time management.

In the general practice setting, detailed records may be available to assist in assessing the traveller’s medical risks for travel. In any event, these records may need updating if the traveller has not presented to the GP for some time. Travel clinics, general practices and those in the travel industry should make it clear to prospective travellers that they should present early before travel, to obtain their travel medicine advice, immunisations and chemoprophylaxis or be referred for specialist advice, such as a pre-travel dental check. This may be best stated in a formal practice policy, so that travellers are aware of these possible requirements, which might be advertised in clinic newsletters, websites or practice updates or reminders.

ESTABLISHING THE RISKS

The risks of travel that need to be assessed for most travellers include the risks of the:

• destination

• mode of travel

• traveller’s medical history

• intervention.

It is important in travel medicine to establish the risks of the destination and the mode of travel in terms of the hazards and the potential exposure to these hazards, and to examine the traveller’s medical history to establish host risks, which may affect selection and use of interventions in the pre-travel health consultation. These are then weighed against the risks of the intervention.

The risks of the destination and any specific requirements for travel health advice may be obtained from a variety of resources. The WHO publishes a booklet entitled International Travel and Health.¹² Several other publications and sources of information relevant to travel medicine are also available. Online computerised databases have long since been mooted as useful aids for providing the most up-to-date and validated information for advising on travel medicine.¹³

POST-TRAVEL CONSULTATION

The traveller should also be advised of the possible need for follow-up and management after travel, particularly if going to a high-risk area (e.g. for malaria) or if they have any illness upon return (e.g. fever; persistent or bloody, mucous diarrhoea).¹⁴ It must be impressed upon the traveller that, in the event of any illness upon return, they should inform the treating physician of their recent travel and that they have travelled, for example, to a malaria area. It is important, if seeing a traveller with a post-travel health problem, that a risk assessment similar to the pre-travel health consultation is undertaken, guided by the presenting features of the illness or injury against a background of the patient’s general health. Even travellers who have been seen in the clinic or general practice for pre-travel health advice may need to have the risk assessment re-evaluated if any of the parameters of risk have changed (e.g. the person has travelled to a new destination). The risks of travel may also be modified by:

• having travel insurance and access to an emergency assistance service

• post-travel screening and interventions

• malaria eradication

• empirical eradication treatment (e.g. deworming treatment).

The effective early management of post-travel health problems early can significantly reduce morbidity and mortality, among travellers, from diseases such as malaria, which may still occur post travel as no intervention is necessarily 100% protective. Managing the risk and these travel health problems in a timely manner can also reduce the risk to local populations from this disease, and post travel it may assist in reducing the risks to the traveller’s own community (e.g. in dengue recognition and management).

DEVELOPMENTS IN TRAVEL MEDICINE

Several key developments in the past two decades have ensured the continuing emergence of travel medicine as a specialty area. The development of national programs and guidelines in travel health was an important advance, as this recognised the need to develop a consensus strategy for combating commonly encountered infectious diseases and other problems encountered by travellers. Examples of these include the former Australian Government’s Travel Safe® Programme, including the publication of Australian guidelines for travel health,¹⁵ and the US Centers for Disease Control and Prevention (CDC) travel health program.¹⁶ These programs and guidelines were directed at the major providers of travel health advice, such as general practices and public health agencies, but also travel clinics and travel agents. Internationally, the World Health Organization has also been producing travel health guidelines. (Examples of major travel health guidelines can be found in the Resources list.)

Three main challenges confront effective travel medicine practice.

• Travellers must recognise the need for travel health advice before travelling abroad, particularly given that a recent airport survey suggested that only 50% of international travellers abroad had sought pre-travel health advice.¹⁷

• Travellers need to seek travel health advice in a timely manner, preferably 6–8 weeks before travel.

• Travellers should obtain travel health advice from a qualified source. In the survey previously mentioned, only one-third of travellers had sought pre-travel health advice from a healthcare professional.¹⁷

Many of these challenges can be at least partially addressed through industry and government cooperation, particularly at the level of the travel agent or airline, which have initial contact with travellers. Many countries now have foreign travel advisory services that help keep practitioners advised about things such as important travel warnings and global disease outbreaks.

One of the most important factors influencing whether travellers seek health advice is the perceived risk and severity of tropical diseases,¹ despite their relatively low health and safety risk to travellers compared with accidents and less exotic conditions such as traveller’s diarrhoea. In addition to the prevention of potentially lethal diseases and injuries among travellers abroad, the importance of providing travel health services is also increasingly being recognised in relation to early detection and reporting of imported infections.

PROFESSIONAL INITIATIVES

The International Society of Travel Medicine (ISTM), established in 1991, has taken the lead in establishing a global professional base for travel medicine. Some of the important early initiatives of the ISTM were the provision of travel health alerts to subscribers, a journal, biennial conferences, a global listing of travel health practitioners, and a collaborative disease-reporting network (GeoSentinel) with the CDC in the United States.¹⁸ GeoSentinel has played a role regionally in examining post-travel health problems.¹⁹ More recently, the ISTM has developed a certification program based on a detailed body of knowledge in travel medicine leading to a Certificate of Travel Health.²⁰ GeoSentinel is an excellent example of the contribution of travel medicine to the early detection and reporting of imported infections, to which several sites in Australia and New Zealand contribute.²¹

The Asia Pacific Travel Health Association also conducts biennial conferences in travel medicine in the Asia-Pacific region, in alternate years to the ISTM’s annual conference and in parallel with its endorsed regional conference. The two major journals in travel medicine are currently the ISTM’s Journal of Travel Medicine, published by Wiley-Blackwell, and Travel Medicine and Infectious Diseases, published by Elsevier Science. In Australia, the development of a professional body in travel medicine, the first Faculty of Travel Medicine (FTM), has been achieved ²² as part of the Australasian College of Tropical Medicine (ACTM). The FTM works in close association with the New Zealand Society of Travel Medicine, established in 1997. The ACTM produces the Annals of the ACTM, which is subtitled ‘A journal of tropical and travel medicine’, reflecting the major interests of the college and its faculty. The Royal College of Physicians and Surgeons of Glasgow subsequently founded an FTM in 2006.

In addition, there are a number of valuable internet and related resources, which also provide information on disease distribution and prevention (see Resources list). Access to current policy guidelines and up-to-date health intelligence, usually provided in travel medicine from internet-based resources, is essential. Continuing research is essential for a better understanding of the epidemiology of travel-related diseases and injuries, which in turn leads to the development of improved guidelines in travel medicine and more effective preventive measures to combat infectious diseases and prevent injuries associated with travel.

VECTOR-BORNE DISEASES

Vector-borne diseases remain among the great personal concerns for travellers abroad, especially those travelling to more remote tropical areas. Some vector-borne diseases also represent a potential public health problem when returning home. Malaria remains the single most important vector-borne disease problem, although arboviral diseases such as dengue and Japanese encephalitis (JE) are also becoming increasingly important international travel-related health problems. Some vector-borne diseases are important for local travel within a country or region—an example is scrub typhus, which has affected soldiers in northern Queensland, Australia.^23,²⁴

Personal protective measures remain the first line of defence for vector-borne diseases. Travellers need to be aware of when the vectors bite and the seasonal nature of some of these vectors. Table 45.2 summarises the biting behaviour of mosquitoes that carry major diseases. Other vectors also have peak biting times between dusk and dawn (e.g. phlebotomine sandflies transmitting leishmaniasis). Preventive measures are mostly directed at reducing contact with vectors, such as: staying in screened or air-conditioned accommodation where possible; spraying the accommodation area; using permethrin-impregnated clothing to cover as much of the body as possible; using diethyl methyl toluamide (or DEET) repellents; controlling vermin and stray animals; and using bed nets soaked in permethrin, and fine-mesh bed nets to prevent sandfly bites. Currently available non-DEET repellents do not provide protection for durations similar to those of DEET-based repellents.²⁵ For example, a number of citronella products have been tested, but these give very short-term protection.²⁵ Soybean oil (2%) provides some protection, but again of much shorter duration than DEET-based products.²⁵ More recently, 20% Citrodiol®, a lemon-eucalyptus extract, has been found to be as effective as DEET in preventing mosquito and other insect bites and provides about 7–8 hours protection.²⁶

TABLE 45.2 Time of peak biting activity of mosquito genus by disease

Mosquito genus	Peak times of activity	Examples of diseases transmitted
Anopheles	Usually night (‘dusk to dawn’), mainly rural	Malaria, lymphatic filariasis
Culex	Usually evening/night (‘dusk to dawn’)	Japanese encephalitis, West Nile virus, lymphatic filariasis
Aedes	Usually day biting, midday	Dengue, yellow fever, lymphatic filariasis
Mansonia	Usually night	Lymphatic filariasis

MALARIA

Malaria is a serious disease caused by a protozoan parasite largely confined to the tropics. The WHO estimates that there are more than 500 million cases of malaria infection and 2.5 million deaths due to malaria worldwide annually.²⁷ Most cases and deaths occur due to infection with Plasmodium falciparum species of malaria, although infection due to P. vivax also remains important, especially as dormant liver stages of the life cycle can cause relapses, sometimes several, for months after returning home. While Australia is malaria-free, suitable vectors of the Anopheles mosquito can be found in many parts of tropical northern Australia, resulting in occasional reports of local transmission from imported cases of malaria.^28,²⁹

Standard malaria preventive measures are considered part of pre-travel health planning for travellers to malaria areas, based on disease patterns and policy guidelines. Current disease-prevention measures against malaria include the use of malarial chemoprophylaxis, personal protective measures against insect bites, environmental health measures against disease vectors, malaria eradication treatment for liver stages, including hypnozoites, and gametocyes on return from the malaria area, and early detection and treatment of malaria cases in order to avoid serious complications of the infection.

The growing incidence of chloroquine and multiple drug resistance in P. falciparum and, more recently, P. vivax have limited the antimalarial drug options for malaria chemoprophylaxis. Current recommended malaria chemoprophylaxis options include doxycycline (one 100 mg tablet daily), mefloquine (one tablet weekly), and atovaquone plus proguanil or Malarone® (one tablet daily, consisting of 250 mg of atovaquone and 100 mg of proguanil).¹⁶ Chloroquine continues to be recommended as malaria chemoprophylaxis for malaria in the few areas where there is no chloroquine resistance.

Malaria eradication

Current eradication treatment for malaria is primaquine (two 7.5 mg tablets twice daily for 2 weeks), although tafenoquine was trialled in defence force personnel in East Timor as both an alternative eradication treatment (400 mg daily for 3 days) and a weekly-dose chemoprophylactic agent.³⁰

Because of the incidence of neuropsychiatric side effects, such as anxiety and nightmares, it is advisable for travellers taking mefloquine for the first time to take several trial doses, possibly commencing as early as 3 weeks before departure.³¹ It is also advisable that travellers are given trial doses of other antimalarials, such as doxycycline and Malarone®, that they might be taking for the first time well before departure. This is to ensure that there is time to consider alternative chemoprophylactic drugs.³¹ If travel is commenced at short notice, modification to antimalarial regimens may have to be done abroad, which is less satisfactory. There are varying opinions on how long antimalarial drugs should continue to be taken after leaving an antimalarial area. However, antimalarial drugs that have no pre-erythrocytic effects on the liver stages of the malarial parasite, such as doxycycline and mefloquine, should be continued for up to 4 weeks afterwards. This relates to the time it takes for parasites to develop in the liver and infect the bloodstream. Chemoprophylaxis with Malarone®, which also has some effects on the hepatic stages of P. falciparum parasites, may be able to be given for shorter periods (e.g. one week) after return.³²

For travellers to more remote areas, standby treatment in the event of overt malaria infection while abroad may also be useful. ‘Standby treatment consists of a course of antimalarial drugs that travellers to malaria endemic areas can use for self-treatment if they are unable to gain access to medical advice within 24 hours of becoming unwell.’^31a In these situations, a traveller’s medical kit may be supplied with a thermometer, possibly an immunochromatographic test (ICT) malaria diagnostic kit and written instructions, and an appropriate malaria treatment course and written instructions, and the traveller must seek medical advice as soon as possible. Newer antimalarials that may be useful for standby treatment include Malarone® and Riamet®, the latter containing 20 mg artemether and 120 mg lumefantrine.³³

ARBOVIRAL DISEASES

There are many arboviral diseases that may affect travellers. Apart from yellow fever, which has a widespread distribution in many parts of South America and Africa and is controlled by international health regulations,³⁴ two of the most important arboviral diseases for travellers are dengue fever and Japanese encephalitis, because in recent years people have been travelling to more remote areas where these diseases are endemic. Both diseases are transmitted by various species of mosquitoes.

Dengue fever is a major global public health problem. The WHO estimates that there are more than 50 million cases per year.³⁴ Dengue is a viral illness transmitted by Aedes mosquito species, classically Aedes aegypti. Infection may range from subclinical to fever, arthralgia and rash, or be complicated by haemorrhagic diatheses or shock syndromes. Treatment is supportive, while management of the problem is directed towards early detection of the disease and preventing transmission upon return to receptive countries.³⁵ Numerous outbreaks of dengue have been attributed to travellers returning with the disease, associated with delays in detecting the condition.³⁵ With travellers arriving or returning from abroad during the incubation period of the disease, it is vital that there is a collaborative effort made by various civilian public health authorities to contain and prevent the transmission of the disease among the local population.³⁶ Until a vaccination becomes available, the mainstays of dengue prevention are personal protective measures and environmental health measures against disease vectors.³⁵

Japanese encephalitis (JE) is the leading cause of viral encephalitis in Asia. The WHO estimates that there are more than 70,000 cases annually in South-East Asia.³⁷ Up to a third of clinical cases die and about half of clinical cases of JE have permanent residual neurological sequelae.³⁷ Despite the availability of a vaccine against JE, the immunogenicity of these vaccines has recently been questioned and concerns have been raised regarding adverse reactions reported with vaccination.³⁸ The current development of safer and more immunogenic second-generation JE vaccines will be important for travellers in this region in the future.³⁷

PREVENTION OF INFECTIOUS DISEASES THROUGH VACCINATION

A number of infectious diseases of travellers can be prevented by immunisation. There are few mandatory vaccines, for which certification is necessary, and these include yellow fever and meningococcal meningitis. Yellow fever vaccination is required for all travellers entering or returning from a yellow fever endemic area, which is prescribed by the WHO.^27,³⁹ Meningococcal vaccination is required for travellers to Mecca.²⁷

The travel medicine consultation is also an opportunity to update routine and national schedule vaccinations for diseases that may afflict travellers anywhere. There are also a variety of vaccinations that may be required for travellers to particular destinations. It would seem prudent to vaccinate travellers against diseases that might be acquired through food and water, such as hepatitis A, typhoid and polio,³¹ as well as using other measures to combat these diseases. The most common vaccine-preventable diseases of travellers are hepatitis A and influenza³; however, typhoid vaccination should also be considered for travel to many developing countries. Polio vaccination is rarely required these days, with a concerted campaign for global eradication; however, it may be required in situations where polio outbreaks have been reported.³¹

There are a number of other infectious diseases, such as hepatitis B, JE and rabies, that may afflict travellers to certain destinations or are a result of the nature of their travel and are vaccine preventable (see Table 45.1).

For older travellers, pneumococcal and influenza vaccinations should also be considered. The development of combination vaccines, such as hepatitis A plus typhoid and hepatitis A plus B, has greatly reduced the number of injections required.³¹ The development of rapid schedules for travellers departing at short notice has been useful in providing protection within 4 weeks.³¹ Many diseases have no vaccination. For example, some parasitic diseases, such as intestinal and filarial helminths, can only be prevented through personal protective measures against the infective stages of the parasite and/or through periodic treatment or eradication treatment on return.

TRAVELLER’S DIARRHOEA

Traveller’s diarrhoea (see Ch 30, Gastroenterology) is a common problem for travellers and emphasises the importance of being able to communicate basic public health advice to the individual. It also highlights the need for a sound knowledge of tropical diseases. In general, reference may need to be made to:

• water sources and water purification, which may involve the use of both filters and compounds such as iodine, or advice on how to boil water

• specific diseases and the consequences of diseases potentially acquired from food and water

• oral rehydration salts and their use

• the need for antibiotic prophylaxis

• selection and use of anti-motility drugs

• selection and use of standby antibiotic drugs

• awareness that some foods, such as some cereals, nuts, seeds and spicy foods containing chilli or ginger, may contain aflatoxins, which may be a non-pathogenic cause of diarrhoea

• the possible role of probiotics in preventing traveller’s diarrhoea.

A recent meta-analysis suggested that several probiotics have significant efficacy in preventing traveller’s diarrhoea, in particular Saccharomyces boulardii and a mixture of Lactobacillus acidophilus and Bifidobacterium bifidum.⁴⁰

Despite the importance of advice concerning the prevention of traveller’s diarrhoea, it is interesting to note that constipation is also of considerable inconvenience for travellers, and may also need attention.

NON-INFECTIOUS HAZARDS OF TRAVEL

Despite the emphasis on infectious disease in travel medicine, the single most common preventable cause of death among travellers is accidental injury.^8,⁴¹

The patterns of mortality among travellers from the United States, Switzerland, Canada and Australia are similar. This is illustrated by research indicating that about 35% of deaths of Australian travellers abroad were the result of ischaemic heart disease, with natural causes overall accounting for some 50% of deaths.⁸ Trauma accounted for 25% of deaths abroad.⁸ Injuries were the reported cause of 18% of all deaths, with the major group being motor vehicle accidents, accounting for 7% of all deaths, which appeared to be over-represented in developing countries.⁸ Infectious disease was reported as the cause of death in only 2.4% of those who died while travelling abroad.⁸

A similar pattern of mortality was observed in Swiss,⁴¹ American⁴² and Canadian⁴³ travellers abroad. Deaths of travellers have also resulted from air crashes, drowning, boating accidents, skiing accidents, bombs and electrocution.⁸ Homicides, suicides and executions combined accounted for about 8% of all deaths.⁸ Most fatal accidents in American and Swiss travellers were traffic or swimming accidents.^41,⁴² Deaths of tourists visiting Australia were similarly found to be due mainly to motor vehicle accidents and accidental drowning.⁴⁴

ISSUES IN AVIATION MEDICINE AND ALTITUDE

Travel medicine is also a key component of the activities of many healthcare professionals working in aviation medicine. In addition to undertaking aviation medical examinations and advising their own staff who are travelling, airline medical departments review passengers’ clearances to fly and provide advice to travel health advisers. Some travellers need special clearance to fly in cases of aeromedical evacuation (AME) on commercial aircraft and in certain prescribed circumstances of normal travel, such as after recent surgery or with serious physical or mental incapacity,⁴⁵ and liaison by travel health advisers with the airline medical departments is usually advisable. Healthcare professionals working in aviation medicine also become involved in developing policies and guidelines for dealing with in-flight emergencies involving travellers as well as training in first aid for flight attendants. Physicians working in aviation medicine have their own national or regional professional organisations.

While some medical practitioners undertake the work of Designated Aviation Medical Examiners,⁴⁶ particularly in respect of pilots, air traffic controllers and, in some instances, flight attendants, travel health advisers also need to be aware of the potential health effects of modern airline travel. These include the effects of reduced atmospheric pressure, low humidity, closed environment, inactivity, the effects of crossing several time zones on circadian rhythm, alcohol, and the general effects of aircraft motion and movement.⁴⁷ These effects can produce conditions such as barotrauma, dehydration, jet lag, motion sickness, claustrophobia and panic attacks, air rage and spread of infectious disease, and can contribute to the development of deep venous thrombosis (DVT) and venous thromboembolism (VTE).⁴⁷ Concerns have also been raised about the transmission of tuberculosis through close proximity to infected travellers on commercial aircraft.⁴⁸ The provision of travel health advice and preventive measures for these conditions also largely falls to the travel medicine provider.

While considerable attention has been focused on DVT and VTE, it remains uncertain what the contribution of air travel is to the development of this condition among travellers. What seems to be clear is that the development of DVT and VTE is multifactorial.⁴⁹ While the identification of travellers with predisposing risk factors would seem useful, it is only an option where the risks of side effects of the screening procedure do not outweigh the risks of developing DVT after a long-haul flight, which is estimated to be about 1 in 200,000 for travellers on a 12-hour long haul journey.⁵⁰ In the meantime, conservative measures should be recommended, such as in-flight exercises, restriction of alcoholic and caffeinated beverages and drinking lots of water. Other preventive measures for some at-risk cases, such as subcutaneous heparin, are worthy of investigation.³¹ Current epidemiological research and pathophysiological studies are helping to establish which travellers are at greatest risk, which will in turn lead to appropriate intervention studies.

One of the most interesting problems in travel medicine has been the prevention of altitude illness. It has been difficult to find associations that might be useful in screening for individuals at higher risk; hence the focus has been on early treatment or the use of prophylactic agents such as acetazolamide. Natural compounds have been explored and Ginkgo biloba has been widely used; however, a recent trial suggested that Ginkgo biloba performed very poorly compared with drugs such as azetazolamide.⁵¹ Further studies are probably needed in human populations at risk.

TRAVEL ADVISORIES

In recent times, travel advisories have assumed great importance in endeavouring to ensure the safety and security of travellers. Travel advisory services include the US State Department,⁵² the Australian Department of Foreign Affairs and Trade,⁵³ and the UK Foreign and Commonwealth Office.⁵⁴ Travellers have suffered numerous casualties from recent acts of terrorism, most notably the Bali bombings, and natural disasters, most notably the Asian tsunami, both of which required a rapid multiagency response to rescue travellers from the affected areas.⁵⁵^–⁵⁷

TRAVEL INSURANCE

Because of the potentially high costs of medical and dental treatment abroad, which may not be covered by private health insurance or local national health services, and the potential high costs associated with AME, all travellers should be advised of the need for comprehensive travel insurance. Travel insurance policies normally underwrite travel-related, medical and dental expenses incurred by travellers abroad under conditions specified by the travel insurance policy. In addition, travel insurance companies often provide a direct service, usually through their emergency assistance service contractors, to assist travellers abroad. This may include assistance with accessing or obtaining medical care while overseas, including AME. For example, claims for reimbursement of medical and dental expenses abroad made up more than two-thirds of all travel insurance claims in Australia and Switzerland.^6,⁷ In the Australian study, almost one in five Australian travellers abroad had been found to have used the travel insurer’s emergency assistance service.⁶

Travel insurance is the most important safety net for travellers in the event of illness, injury or unforeseen events, and should be reinforced by GPs and travel health advisers. Studies have shown that about 60% of GPs in New Zealand,⁵⁸ 39% of GPs in Australia¹⁰ and 39% of travel clinics worldwide⁵⁹ usually advise travellers about travel insurance. Although the majority of GPs also usually advise travellers about ways to find medical assistance abroad,⁵⁸ GPs need to ensure that they provide advice on suitable travel insurance companies, especially as a source of medical assistance while travelling. However, it is not known what proportion of travel agents or airlines currently give advice on travel insurance routinely, although most airlines operating internationally now provide more travel health advice in their in-flight magazines.⁶⁰