The first phase, which began in 1985 and ended in 1988, was marked by a small number of imported cases. The majority of infected persons during this time were foreigners or overseas Chinese, and the cases appeared only sporadically in coastal cities. Four haemophiliac patients infected with HIV through imported factor VIII were reported from Zhejiang.

The second phase, from 1989 to 1993, might be termed a limited epidemic. It began in October 1989 with the identification of HIV infection in 146 drug users in southwest Yunnan. During this phase, the majority of reported HIV infections in China were among drug users in Yunnan. (The estimated prevalence of HIV had been 70-80% among known drug injectors in Ruili, 40% in Longchuan and 0-5% in Luxi, the percentages decreasing as distance from the border with Myanmar increases.) At the same time, a small number of HIV infections were reported among labourers returning from abroad, STD patients and prostitutes.

The third phase began in late 1994 when HIV transmission spread beyond Yunnan Province. A considerable number of HIV infections were reported among drug users and commercial plasma donors from various regions, and national figures for HIV infection quickly grew. Increasing numbers of drug-related HIV infections were reported in Sichuan in 1995, in Xinjiang in 1996 and Guangxi in 1997. At the same time, HIV infection by sexual contact increased, but remained relatively infrequent, and has not yet reached epidemic proportions.

The HIV/AIDS situation in China can be summarized briefly: overall reprted HIV infection is still relatively low, with infections clustered in particular areas, the majority of them rural, but the many known routes of transmission now cover broad areas of the country; all indications point to a major epidemic in the near future.

There are two possible reasons for low reported numbers and both are in fact likely:

• The numbers actually are relatively low; HIV/AIDS infection in this population is still in a fairly early stage;
• There is widespread underreporting of cases,

The distribution of cases shows 30 out of 31 provinces, municipalities and autonomous regions reporting HIV infections, the majority of them in limited areas within the province or region. Many of those people now infected are rural residents. Increasing numbers of cases in other areas, however, especially along major transport routes, due to infections among transport workers and migrants, suggest that incidence will soon be far more widespread.

People infected with HIV come from all occupations, but the majority are farmers, returning overseas labourers, unemployed people and private businessmen. Young adults account for most of the infections: as many as 79% of reported HIV carriers are aged 20-40. Males outnumber females by about five to one. Of reported cases of HIV infection, roughly two-thirds are due to injecting drug use and 8% to sexual contact. To date there have been three reported cases of mother-to-child transmission.

In the areas of greatest rates of infection in Yunnan and Xinjiang, the majority of cases are among injecting drug users. In some provinces of central China, a number of HIV infections are among commercial plasma donors. These commercial plasma donors are often recruited by illegal plasma collecting companies from among mobile populations who sometimes also engage in prostitution and drug abuse. In a number of instances, HIV infection could be traced to contaminated needles and equipment used in illegal commercial plasma collecting settings.

Whatever the number of HIV infections finally reached in China, since AIDS cases are essentially the HIV infections of five to ten years earlier, we can expect a corresponding explosion in the number of cases of AIDS in the years to follow, and similar epidemic increases in the diseases associated with HIV infection and AIDS, particularly tuberculosis and other opportunistic infections.