Travel to tropical, culturally diverse and remote countries that do not have fully developed public health infrastructures or medical services, has become more common. Warm climates, and places with poor sanitation and hygiene systems increase the risk of travellers' diarrhoea. Causes and transmission Diarrhoea is caused by bacteria, viruses, protozoa and algae-like organisms, which vary in prevalence at particular locations and times of the year. The most common organism responsible for travellers' diarrhoea is Escherichia coli. Transmission is mainly through the faecal-route, where organisms are carried from hand to mouth, or by contaminated food and drink.
Flies can spread disease from excrement to uncovered food.
Viruses or toxins can be present in shellfish, which filter pollutants coming from sewerage outlets. Risk of transmission depends on local public health systems, how food and drink is prepared, and environmental hygiene. Factors affecting incidence Local incidence rates range from 20 to 80 per cent and are determined by the prevalence of endemic disease, climate, and public health infrastructure. In addition, the number of flies increases at warmer times of the year, resulting in increased transmission and more episodes of diarrhoea. Young travellers tend to be less cautious and are more likely to get travellers' diarrhoea.