How urbanization affects the epidemiology of emerging infectious diseases

Neiderud, Carl-Johan

About a century ago, only 20% of the world's population lived in cities, and in the least developed countries the percentage was only 5% (6) . Approximately half of the world's population now live in these urban centres. The two inhabited continents, which currently are the least urbanized, are Asia and Africa, with respectively 48 and 40% of the population living in cities. These percentages are expected to rise dramatically by the year 2050 to 64 and 56% respectively (1) . In the last decade, the growth in the urban population has been the highest in Asia, adding 0.88 million urban migrants per week. Africa was the second highest contributor with 0.23 million. The total figure of new urban residents per week during the last decade was on average 1.2 million. It is in Africa and Asia where the current rapid growth is taking place. 30 years are that almost all of the population growth will be in urban areas, but the growth in developed countries is expected to remain largely unchanged (2) . Chronic illnesses have been increasing in importance for the developing world. Worldwide the leading causes of death in 2011 were ischaemic heart disease followed by stroke, lower respiratory infections, chronic obstructive lung disease, and diarrhoeal diseases. However, if you look at the list for low-income countries, infectious diseases still have a profound impact. The top three causes of death in these settings are all infectious diseases: lower respiratory infections, HIV/AIDS, and diarrhoeal diseases (7) . Many of the lower income countries are expected to have a major growth among the urban population, which leads to considerable challenges for the governments and health care to keep up to pace and develop their social services and health care as these regions grow.