China’s HIV/AIDS epidemic has entered its third phase, moving from ‘‘entry,’’

‘‘spreading,’’ and is now in its ‘‘expansion’’ stage, according to some (Wu, Rou

and Cui, 2004). Previous chapters detailed the role of intravenous drug use (IDU),

commercial sex work (CSW), men who have sex with men, and demographic fac-

tors, particularly the gender imbalance among younger age cohorts in the spread of

HIV. However, the ever growing migrant population is singled out as a key driver

of HIV/AIDS in China during this expansion stage. In Chapter 4, we argued that

the increasing feminization of migration is also linked to the growth of China’s

commercial sex industry and has, consequently, become an important bridge for

the spread of HIV/AIDS to the general population. This chapter considers more

broadly the process of migration with a particular emphasis on national-level pat-

terns of migration. China’s economic reforms have had a large impact on the

movement of people in search of better opportunities. Such large-scale movements

of people have historically played an important part in disease transmission:

The link between commercial activity and transmission of infectious disease

has a long history. Because epidemics depend on the introduction of a patho-

gen into a susceptible population, it is not surprising that global events asso-

ciated with mass movements of people and goods have seen the concomitant

emergence of new threats of infectious disease. Major historical challenges

to public health and subsequent advances in the control of communicable

disease frequently emerged in important trading centres – eg, 14th century

Venice, Italy; 19th century London, UK; and 20th century New York, USA.