Rapid urbanization has significant repercussions on migrants' health. The increasing movement of people from rural to urban areas often alters the characteristic epidemiological disease profile of a country. At the same time, new diseases appear and/or old ones reemerge. Such is the case of HIV/AIDS, tuberculosis (TB) and malaria.

Urbanization is associated with changes in diet and the physical exertion routine, increasing obesity in society and heightening the risk of type II diabetes and cardiovascular diseases.

In China, additional mobility-related risks among migrants include poverty, vulnerability to sexual abuse and exploitation, hazardous working conditions and separation from social support networks. Many of these conditions affect the most vulnerable segment of society: women, children and the elderly.

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More than 100 million people are estimated to have moved from the countryside to rapidly expanding urban centers in the country during the past 20 years.

Although many migrants are young and healthy when they arrive in cities, poor living conditions and overcrowded houses and neighborhoods increase the incidence of diseases such as malaria, typhoid and respiratory ailments. In recent years, for example, the problem of rising TB infection has been compounded by delayed diagnosis and inadequate care.

In addition, migrants show high rates of sexually transmitted diseases, including HIV/AIDS. Because of their high mobility, migrants tend to spread the virus when they return to rural areas, where health facilities are not as well equipped to deal with the infection as they are in cities.

Many migrants' suffer from health problems because they lack knowledge of how to use existing health services. And the high cost of medical care makes many of them reluctant to visit a hospital for treatment.

On most indicators of maternal and infant health, migrants fare worse than urban residents. Many migrant women work in industries where they come in contact with environmental contaminants that are dangerous to their reproductive system, especially if they are pregnant.

Toxic substances in the environment increase the risk of abortion, birth defects, fetal growth and neo-natal death. Many studies have shown that exposure of pregnant women to carbon monoxide can damage the health of the fetus. A developing fetus is susceptible to environmental factors - which it encounters when the mother is exposed to toxic substances at her workplace.