In addition to the existing health status of the traveller, the nature, duration or timing of the trip may have some bearing. Will the traveller be staying in urban or rural areas, and how accessible is medical care locally?

Flu is the most common vaccine-preventable disease. For non-immune Western travellers in tropical or sub-tropical regions, there is around a 1% absolute risk of contracting flu per month of travel. By comparison, traveller's diarrhoea will affect 30% of travellers within two weeks. Flu vaccination is highlighted in travel health literature, especially for those taking a cruise, and those making the Hajj or Umrah pilgrimage to Mecca.19

For typhoid, the risk/month for non-immune Western travellers in South Asia is around 1 in 3,000 but less than 1 in 50,000 for most other destinations.19 In the UK, most cases of typhoid are in people visiting India, Pakistan or Bangladesh.8

For TBE, the risk can be around 1 in 10,000, slightly greater than for hepatitis B. Cholera risk is about 1 in 500,000, while Japanese encephalitis risk is about 1 in 1,000,000. The chances of contracting meningococcal disease, rabies, or polio are less likely, but polio remains endemic in Afghanistan, Nigeria and Pakistan.19,21

In general terms, the travellers with the greatest risk of morbidity are those visiting friends and relatives in their country of origin - with malaria and typhoid particularly notable.1 Travel to north or central Europe, North America or Australia is unlikely to require vaccinations, but check about TBE.