Food and water-borne diseases
Risks are often minimal from food and waterborne disease in urban areas in countries with good infrastructure and high standards of environmental and public health.
Vector borne diseases
In modern cities, there may be less risk from vector-borne diseases such as malaria due to fewer breeding sites. However, this does not mean there is no need to carry out bite prevention measures and mosquitoes also cause outbreaks of diseases such as dengue, yellow fever and Zika virus.
In some cities mosquito-borne diseases are becoming more common due to commuters, trains and other vehicles bringing mosquitoes from the country on a daily basis.
Also in resource-poor countries mosquitoes are likely to be more common in poorer parts of cities where there is less surface water drainage and more breeding sites.
It is mostly long-term expatriates, volunteers, charity and humanitarian aid workers taking on specific rural roles who visit these areas. Short-term holidaymakers rarely visit rural areas except when in transit between airports and tourist resorts so exposure is limited.
Accommodation in rural areas is likely to be of a poorer standard and the risk of contamination of food and water greater.
Road accidents in rural areas are likely to be more serious than in cities because of the speed of the traffic.
Insect vectors of infection such as ticks, various flies and mosquitoes are usually more common in rural areas than in modern cities since there are more breeding sites.
Atmospheric pollution from heavy traffic and poorly maintained vehicles is an increasing problem throughout the world in urban areas often more so in developed countries with poorly maintained buses, taxis, cars and lorries.
The main culprit appears to be nitrogen oxides from diesel engines.
The problem is worse in cities on calm days when the atmospheric pressure is high and little wind to dissipate the fumes.
In some cities airports are regularly closed due to smog-causing poor visibility - a reminder of the days in the UK when there was often dense smog from smoke in cities due to coal burning.
Air pollution is very unpleasant as well as causing lung disease in the long term. In the short-term, those with respiratory problems can find asthma or shortness of breath exacerbated.