Depending on the travel destination, travellers may be exposed to a number of infectious diseases; exposure depends on the presence of infectious agents in the area to be visited. The risk of becoming infected will vary according to the purpose of the trip and the itinerary within the area, the standards of accommodation, hygiene and sanitation, as well as the behaviour of the traveller. In some instances, disease can be prevented by vaccination, but there are some infectious diseases, including some of the most important and most dangerous, for which no vaccines exist.
As many of such diseases are infections, general precautions can greatly reduce the risk of exposure to infectious agents and should always be taken for visits to any destination where there is a significant risk of exposure, regardless of whether any vaccinations or medication have been administered.
Modes of transmission and general precautions
The modes of transmission for different infectious diseases are diverse:
- Foodborne and waterborne diseases transmitted by consumption of contaminated food and drink.
- Vector-borne diseases transmitted by insects such as mosquitoes and other vectors such as ticks.
- Diseases transmitted to humans by animals (zoonoses), more particularly through animal bites or contact with animals, contaminated body fluids or faeces, or by consumption of foods of animal origin, particularly meat and milk products.
- Sexually transmitted diseases passed from person to person through unsafe sexual practices.
- Bloodborne diseases transmitted by direct contact with infected blood or other body fluids
- Airborne diseases involving droplets and droplets nuclei. Droplet nuclei <5 µm in size are disseminated in the air and breathed in. These droplet nuclei can remain suspended in the air for some time. Droplet nuclei are the residuals of evaporated droplets. Droplet transmission occurs when larger particles (>5 µm) contact the mucous membranes of the nose and mouth or conjunctivae of a susceptible individual. Droplets are usually generated by the infected individual during coughing, sneezing or talking.
- Diseases transmitted via soil include those caused by dormant forms (spores) of infectious agents, which can cause infection by contact with broken skin (minor cuts, scratches, etc).
General precautions to prevent infections are outlined in the Chapter 5 of the international travel and health situation publication.
Non vaccine-preventable diseases
The main infectious diseases to which travellers may be exposed, and precautions for each, are detailed in the Chapter 5 of the International travel and health situation publication. The most common infectious illness to affect travellers, namely travellers’ diarrhoea, is covered in Chapter 3 of the International travel and health situation publication (WHO). Because travellers’ diarrhoea can be caused by many different foodborne and waterborne infectious agents, for which treatment and precautions are essentially the same, the illness is not included with the specific infectious diseases.
Information on malaria, one of the most important infectious disease threats for travellers, is provided separately (WHO).
The infectious diseases listed below have been selected on the basis of the following criteria:
- Diseases that have a sufficiently high global or regional prevalence to constitute a significant risk for travellers;
- Diseases that are severe and life-threatening, even though the risk of exposure may be low for most travellers;
- Diseases for which the perceived risk may be much greater than the real risk, and which may therefore cause anxiety to travellers;
- Diseases that involve a public health risk due to transmission of infection to others by the infected traveller.
- Haemorrhagic fevers
- Hantavirus diseases
- Hepatitis C
- Hepatitis E
- HIV/AIDS and other sexually transmitted infections
- Leishmaniasis (cutaneous, mucosal and visceral forms)
- Leptospirosis (including Weil disease)
- Lyme Borreliosis (Lyme disease)
- Lymphatic filariasis
- SARS (Severe Acute Respiratory Syndrome)
- Schistosomiasis (Bilharziasis)
- Typhus fever (Epidemic louse-borne typhus)
- Zoonotic influenza
Some of the diseases included in this chapter, such as brucellosis, HIV/AIDS, leishmaniasis and TB, have prolonged and variable incubation periods. Clinical manifestations of these diseases may appear long after the return from travel, so that the link with the travel destination where the infection was acquired may not be readily apparent.
- Hepatitis A
- Hepatitis E
- Japanese encephalitis
- Meningococcal disease
- Tick-borne encephalitis
- Typhoid fever
- Yellow fever
Information about available vaccines and indications for their use by travellers is provided in the pdf entitled vaccine-preventable diseases and vaccines beside. Advice concerning the diseases for which vaccination is routinely administered in childhood, i.e. diphtheria, measles, mumps and rubella, pertussis, poliomyelitis and tetanus, and the use of the corresponding vaccines later in life and for travel, is also given in the section Vaccines.