A key reason for identifying imported infection is to minimise the chance of onward transmission to the local population by appropriate treatment and isolation of the index case. One of the earliest examples of this was the 40 day (quarantine) period of detention offshore, introduced for ships arriving in Venice and Rhodes in 1377 to prevent the importation of plague. Similar detailed modern regulations exist for containment of specific pathogens that are rarely imported but are of public concern, such as the viral haemorrhagic fevers (Centers for Disease Control, 1995; Advisory Committee on Dangerous Pathogens, 1996). Travel histories of relatives and friends should always be considered when dealing with patients with a potentially infectious disease, particularly in groups such as students or immigrants who have frequent contact with international travellers.
A 24-year-old woman of Indian ethnic origin was admitted to hospital in Liverpool with 1 week of illness typical of acute viral hepatitis. She and her husband (also of Indian ethnic origin) had both been born and brought up in the UK. Her husband had returned from his first trip to India 2 months before, and had been managed at home with probable hepatitis starting 1 month before. She was confirmed as having hepatitis E, imported by her husband.
Hepatitis E is not a common diagnosis in Western countries unless the patient has travelled overseas (Schwartz et al., 1999). This case illustrates the importance of taking a good contact and travel history in all patients.
Travel histories should be relayed to diagnostic laboratories, so that the relevant tests are performed to diagnose exotic pathogens that might otherwise not be sought. This is also essential because of the potential risk of many pathogens to the laboratory workers themselves, including especially brucellosis, transmission of which is common in laboratories in endemic areas and is also a hazard when incorrectly identified samples are sent internationally (Pike, 1978; Luzzi et al., 1993). Apart from exposure to airborne pathogens such as brucellosis, laboratory workers are at special risk from inoculation accidents involving exotic pathogens, such as malaria, trypanosomiasis and leishmaniasis, which will require urgent specialist advice (Lettau, 1991). Failure to diagnose the index infection can lead to tragic consequences in health care workers involved in needlestick incidents.
A doctor in Sicily suffered a needlestick injury while attending a patient with fever imported from Africa. The patient's malaria was subsequently diagnosed and treated in London, but by then the doctor had died from undiagnosed malaria (Communicable Disease Report, 1997).
Exotic infections can travel with their vectors and the hazards of imported zoonotic infections have been highlighted by the recent epidemics of Rift Valley fever in the Yemen and Saudi Arabia, related to imported livestock (Arishi et al., 2000). Similar concerns accompany international movement of domestic pets; this is a particular issue for countries such as the UK that are currently rabies-free and whose regulations relating to pet movement are being relaxed, allowing exposure of animals to a variety of other infections as well as rabies, some of which have potential for spread to humans (Trees and Shaw, 1999). Exotic pathogens may be imported with other animals, such as psittacosis associated with a variety of birds and salmonellosis with reptiles.
Insect vectors survive travel despite regulations designed to hinder them, such as spraying vehicles moving out of the trypanosome belt in Africa, or spraying aeroplanes to kill mosquitoes. So-called 'airport malaria' affecting nontravellers has been reported from several countries that do not usually have local malaria transmission (Gratz et al, 2000).
These imported hazards will only be considered by the health care worker who keeps an open mind and thinks laterally about the situation of the patient. This is not so easy in the growing number of cases of illness caused by pathogens imported with food, identification of which requires sophisticated public health surveillance mechanisms (Nichols, 2000).
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