Epidemiology

Rates vary widely depending on the travel destination.[9] Destinations can be ranked as low-risk (<10% of travellers affected), moderate-risk (10% to 20% of travellers affected), and high-risk (>30% of travellers affected), depending on their level of development. In some high-risk areas, TD incidence exceeds 60%.[10]​ Negligible to very low-risk destinations include northern Europe, Australia, New Zealand, the US, Canada, Singapore, and Japan. Moderate-risk (transitional) destinations include the Mediterranean region, South Africa, and the Caribbean. High-risk destinations include South and Southeast Asia; Central and South America; and East, West, and North Africa.[4][11]​​​ It is estimated that less than 10% of cases of TD are dysenteric.[10]

Seasonal variations in risk occur, (e.g., in South Asia), TD incidence is higher during the hot months before the monsoon.[2] Hot and wet climate conditions are generally believed to support increased transmission of common bacterial pathogens.[12] Incidence of TD is lower in winter.[10]​​​

Risk factors include younger age, adventure travel, visiting friends and relatives, use of proton-pump inhibitors, and lack of caution in food and water selection.[2][9]​​​​ Although some limited resistance to TD develops over time, this is quickly lost after moving to a location with a higher level of water, sanitation, and hygiene (WASH) infrastructure. Prior residence in a higher-risk destination increases the likelihood that the traveller will be less discriminating with their food and water selection. Returning former residents may be more likely to develop TD than tourists, because their previous immunity is no longer present.

Travel to a tropical country within the last 6 months is protective against TD.[10]

A higher prevalence of TD has been noted in deployed military populations and can lead to a decline in job performance or loss of duty days.[4][13][14]​​

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