Summary Review Of HIV/AIDS In Hong Kong 2002

Extract from HIV Surveillance Report -2002 update
Surveillance Team, Special Preventive Programme, The Department of Health
Hong Kong Special Administrative Region

HIV/AIDS surveillance systems in Hong Kong

1. The HIV/AIDS surveillance system comprises the following programmes: (a) HIV/AIDS reporting; (b) Seroprevalence studies; (c) STD surveillance and (d) Behavioural surveillance and other research activities. Surveillance activities are undertaken through the Surveillance Office of the Special Preventive Programme, Department of Health. The tabulated results of the four systems are incorporated in this annual report, while quarterly summary tables can be viewed and downloaded from the Virtual AIDS Office at http://www.aids.gov.hk

2. The HIV/AIDS reporting programme is a dual mechanism involving the voluntary reporting of newly diagnosed HIV and AIDS cases by attending physicians using the DH 2293 form (Appendix I) and by laboratories providing confirmatory tests in the public service. Seroprevalence studies are conducted on selected communities. These include the groups at risk of contracting HIV infection (patients attending the STDs clinics, drug users in methadone clinics and rehabilitation centres), groups without additional risk (blood donors and antenatal women) and in groups whose risk is undetermined (patients with tuberculosis and prisoners). Unlinked anonymous screenings have been applied to enhance our understanding of the HIV situation. STD surveillance is a separate system coordinated in conjunction with the Social Hygiene Service. Finally, behavioural surveillance is a rather new concept in HIV epidemiology. It was initiated as a pilot project in collaboration with the Department of Microbiology of The University of Hong Kong in 1994, and is now a regular programme contributed by different agencies.

Highlights of HIV/AIDS surveillance in 2002

3. In the year 2002, 260 HIV infections have been reported to the Department of Health. This highest yearly figure has put the cumulative total of HIV reports (inclusive of those who had progressed to AIDS) high at 2015. In the same period, there were a total of 53 AIDS reports and the cumulative total has reached 613 (Box 1.1). The first HIV and AIDS case were reported in 1984 and 1985 respectively.

Box 1.1 HIV/AIDS reports in Hong Kong (1984 - 2002)

4. Among the 260 newly reported HIV cases, 201 (77.3%) were male. The male to female ratio was 3.4:1. It denoted the first rebound in the past 6 years during which the male to female ratio dropped from 4.2:1 to 2.9:1. Overall, 71.2% of the HIV reports were Chinese. Yet, only about half of the female were Chinese and more than 40% originated from other Asian countries. The median age at HIV reporting was 34 (interquartile range 28-42), similar to figures in the past years. All cases, except one perinatal HIV infection, reported in the year 2002 were adult cases. The proportion of various sources of reporting was similar to that of previous years. The main source of reporting was public hospitals/clinics/laboratories which altogether reported half of the HIV cases. The Social Hygiene Clinics, the public STD clinics, reported 41 HIV cases (15.8%) in 2002.

5. Sexual transmission remained the commonest reported risk factor for HIV infection locally. Among the 260 new HIV reports, 201 (77.3%) were transmitted sexually, 145 (55.8%) heterosexually and 56 (21.6%) homosexually or bisexually (Box 1.2). It was noted that the proportion of heterosexual transmission gradually decreased from its highest of 70% in 1994 to 56% in 2002. Whereas the proportion of homosexual and bisexual (MSM) transmission slowly crept up from its nadir of around 10% in 1998 to 21% in 2002. The heterosexual to homosexual or bisexual men among the HIV reports in fact decreased from 4.1:1 to 1.8:1 during the same period. The frequency of condom use among men, one of the behavioural markers regularly monitored in HIV surveillance, however, remained similar to that in previous years.

Box 1.2 Reported risks of HIV infection in Hong Kong (1984 - 2002)

6. There has been an increase in number of HIV reports among injecting drug users in recent few years. In 2002, 10 (3.8%) HIV cases reported were transmitted through injecting drug use. This was similar to the figures in 2000 and 2001. Unlinked anonymous testing of methadone clinic attendants revealed a yearly positive rate of less than 0.1% up to 1997. It has been rising gradually to between 0.1 to 0.3% recently. The seroprevalence in 2002 was 0.25%. There has also been an increasing proportion (from about 20% in 1999 to 35% in 2002) of injecting drug users among the new clients known to the Central Registry of Drug Abuse (CRDA). The proportion of needle sharers obtained from the Street Addict Survey (SAS) has also increased from 10% in 2000 to more than 25% in 2002. Although these data may not represent the complete and actual situation of HIV infection among the population of drug users in Hong Kong, they again have alerted us the possible spread of the infection among them locally. The health education and HIV preventive effort is never enough in this very marginalized group in the society. Moreover, it was noted that the number of methadone users participated in voluntary HIV testing decreased from 600 in 1999 to about 300 in 2002. No positive case was diagnosed and reported from any drug related institution in 2002.

7. More physicians are now reporting the CD4 levels at HIV diagnosis to the Department. In recent 2 years, more than 70% of the HIV reports included the CD4 levels at HIV diagnosis. Knowing that these results could be biased towards the more symptomatic patients, the figures might have underestimated the actual immunity level among HIV infected individuals (Box 1.3). Yet, an improving trend of CD4 levels has been observed. The median CD4 level increased from below 100 cells/ul in 2000 to above 200 cells/ul in 2002. The percentage of CD4 >= 200 cells/ul at HIV reporting increased from 41% to 50% in the same period.

8. We continued to observe a gradually decreasing trend in the number of AIDS reports. In fact, the annual reported number of AIDS cases has been stable at 60-70 since 1996, the year when highly active antiretroviral therapy (HAART) was introduced. There were a total of 53 AIDS reports in year 2002. When defining late HIV diagnosis as the reporting of AIDS within 3 months of HIV reporting, the number of late HIV diagnoses actually has remained stable since 1997. There were 52-56 cases reported every year. In fact, 52 (98.1%) of the 53 AIDS reports in 2002 had their AIDS reported within 3 months of HIV reports. That is, nearly all the reported AIDS cases presented late in their course of illness in recent years. This finding suggested that a fraction of HIV infected patients were unaware of their HIV status before they became symptomatic, whereas those who knew that they were HIV positive seldom progressed to AIDS. This is based on the assumption that the level of under-reporting of AIDS cases in the past years has been stable. A previous local study has pointed out that the independent attributes associated with late diagnosis included older age (>35), male sex, Chinese ethnicity and being heterosexual (AIDS Patient Care STDS, under press). Again, the importance of raising the awareness and promotion of early HIV testing in the general public and communities at risk cannot be overemphasized.

9. The primary AIDS defining illness (ADI) patterns of the reported AIDS cases remained similar to previous years. Pneumocystic pneumonia (PCP) (renamed P. jirovechi) continued to be the single most important ADI in the year and accounted for 25 (47%) AIDS cases. This was followed by tuberculosis infection (9, 17%), fungal infections (8, 15%) and penicilliosis (7, 13%). On the one hand, the number of tuberculosis as ADI decreased from around 20 (30%) since 1996 to just 9 (17%) in 2002. On the other hand, unlinked anonymous testing actually demonstrated a seroprevalence of 0.9% among patients with tuberculosis in 2002. This was the highest figure ever obtained since 1990 during which the prevalence fluctuated between 0 and 0.6%. With the approximately 7000 cases of tuberculosis in Hong Kong yearly, it is probable that a significant portion of patients with tuberculosis remain untested and unnoticed of their HIV status.

10. The HIV-1 subtypes of a proportion of the reported HIV infections have been determined in a pilot project jointly conducted by The University of Hong Kong and The Department of Health. Preliminary data of the past 2 years are shown in the table below (Box 1.4). Subtypes CFR01_AE and B have been the most common subtypes identified locally, each accounting for one half and one third of the reported HIV cases respectively. New subtypes of A, AG, BC, B' and D have also been identified in 2002. The CRF01_AE was more common in female, Chinese, heterosexuals and injecting drug users whereas B subtype in male, White and MSMs.

11. Molecular epidemiology is an important tool to identify any common source of HIV infection in Hong Kong. Genetic clustering was found only in a few MSM pairs, perinatal infections and a number of non-Chinese injecting drug users over the past years. There has been no genetic clustering identified among the reported infections in 2002.

Accounting for the increase in HIV reports in 2002

12. Since the implementation of the Universal Antenatal HIV Antibody Testing Programme in September 2001, all expectant mothers attending the public antenatal clinics have been routinely tested for HIV. This has replaced the previous unlinked anonymous screening of the newborn babies first initiated in 1990. It aims to identify the HIV positive pregnant women so that they can benefit from receiving appropriate treatment and perinatal HIV transmission be ideally prevented. Theoretically, the Programme would lead to an increase in HIV diagnosis among women and their partners, at least in the early years of its implementation.

13. A separate system has been set up to monitor the progress of the Programme. So far, less than 4% of the women attending the public antenatal services opted out from the testing programme (Box 1.5). Seven women were diagnosed and reported HIV positive through the Programme in the last 4 months of 2001. An additional 2 partners of these women were also later tested and reported HIV positive in the same year. For year 2002, we received 8 HIV reports from the Programme with another 1 male partner, i.e., an addition of 9 HIV reports in the year. This finding could therefore possibly explain the increases in female HIV cases but not the male cases in the past 2 years (Box 1.6 (a)).

14. In fact, an increase in the number of HIV reports from adult Chinese men was observed (Box 1.6 (c)). While the increase in number of women cases could be attributed to the Programme as mentioned above, the increase in positive cases in men from around 150-170 in the past few years to more than 200 cases in 2002 needs an alternative explanation. Both heterosexual and homosexual transmissions in men increased in the past 2 years. Although the seroprevalence and behavioural studies among people with high risk sexual behaviours have not indicated a remarkable change in the patterns lately, this rising trend in HIV reports among men is worrying. Moreover, the fact that the increase mainly occurred in the young Chinese MSMs (Box 1.6 (d)) and the lack of a regular seroprevalence surveillance system among them make this group particularly vulnerable. It should also be noted that the number with undetermined risk factor continued to increase in the past years. Forty-eight (18.5%) reported cases in 2002 had their risk undetermined.

Conclusions

15. A total of 260 HIV infections, the highest figure ever obtained for a year, were reported in 2002. Cumulative reported number of HIV cases has exceeded 2000. Seroprevalence studies, however, have not indicated a significant increase in HIV seroposivity among at risk groups or the general population. The population seroprevalence remained low at <0.1% in 2002.

16. Sexual transmission, especially among Chinese men, remains an important risk of HIV infection in Hong Kong. Although the results of molecular epidemiology have not indicated any common source of infection locally, the recent disturbing trend of HIV reports among Chinese MSMs has to be monitored.

17. The number of AIDS reports continued to decline, however, the fact that almost all of these cases presented late in their course of illness underscored the importance of early testing and diagnosis. A decreasing trend in the number of voluntary HIV antibody tests done among at-risk groups (e.g. methadone clinics attendants) was observed. With reference to the seroprevalence obtained from unlinked anonymous screening at various sentinel sites (methadone clinics and tuberculosis clinics), a considerable portion of HIV infected persons might have remained undiagnosed in Hong Kong.