The HIV surveillance system comprises 4 main programmes to provide a detailed description of HIV/AIDS situation in Hong Kong. They are (a) voluntary HIV/AIDS case-based reporting; (b) seroprevalence studies; (c) Sexually Transmitted Disease (STD) caseload statistics; and (d) behavioural studies. The data is collected, analyzed and disseminated regularly by staff of the Surveillance team of Special Preventive Programme (SPP), Centre for Health Protection (CHP), Department of Health (DH). At present, the latest HIV/AIDS statistics are released at quarterly intervals at press media briefings and in electronic format (www.aids.gov.hk). Data from various sources are compiled annually and released in the annual HIV surveillance report. This commentary highlights the main findings from HIV/AIDS surveillance activities undertaken in 2004.
Reports of HIV/AIDS cases continue; majority were male, Chinese and of sexual transmission
The Department of Health receives a total of 268 HIV reports and 49 AIDS reports in 2004, a 17% rise in HIV reports and a 12.5% decrease in AIDS reports when compared to figures of the previous year. The cumulated totals have reached 2512 for HIV reports and 718 for AIDS reports respectively. Public clinics/hospitals/laboratories are the primary sources of HIV/AIDS referrals, accounting for nearly half of the HIV reports and 85% of the AIDS reports. When comparing with the average figures from 1984-2004, there is an increase in trend on the number of HIV reports from drug rehabilitation services and AIDS service organizations. The number of reports from other sources such as Social Hygiene Service has remained stable.
In Year 2004, there were 205 HIV reports from men, accounting for 76% of all reports. This represents a 17% rise from last year's figures of 175 cases. The male to female ratio was 3.2:1, the same as last year. About 65% of these reports were believed to have been transmitted sexually, 7.8% through injecting drug use and 28% with risk undetermined. This means that sexual transmission has accounted for more than 90% of HIV reports with identified risks.
Men who have sex with men (MSM) is a rising concern
Both heterosexual transmission and homosexual/bisexual men (MSM) are important risk factors for HIV infection in men (Box 1.1). During the 80s and early 1990s in Hong Kong, there were more males infected from the route of MSM transmission in the HIV epidemic. Since 1993, the trend was reversed with more men found to acquire HIV via heterosexual transmission. Recently, an increasing trend of MSM infected with HIV has been observed with the ratio of heterosexual against MSM dropping from its peak of 4.1:1 in 1998 to 1.1 in 2004. This means that nearly 50% of HIV infected men acquired their infections from MSM transmission. With the increasing trend of MSM infection, it is likely that MSM transmission may overtake heterosexual transmission as the most important risk factor of HIV infection in men (Box 1.2). Apart from an increase of MSM reports in men, the MSM group also shows a younger age distribution when compared with the heterosexual group. (Boxes 1.3 and 1.4)
Cases with undetermined risk factor on the increase
Unfortunately, voluntary reporting is becoming more incomplete as there is an increasing proportion of cases being reported as undetermined risk. For the first time in the history of HIV surveillance, there was over a quarter of the reported HIV cases without a suspected route of transmission. This is especially so for cases without clinical reporting. While it is understandable that the route of transmission may not be determined in every single case, every effort must be made to discern and report this crucial information, so that meaningful aggregate data could be generated and disseminated for better understanding of local HIV epidemiology in Hong Kong.
A proportion presented late with low CD4/AIDS
Report of CD4 level at HIV diagnosis and number of AIDS reports provide useful information on the timing of diagnosis in the course of HIV infection. Sixty three percent of HIV cases in 2004 reported the CD4 level at diagnosis. There is a drop in the proportion of reports with CD4 count mainly due to increased proportion of reports received from private clinics and drug rehabilitation services (Box 1.5).
Box 1.5 ¡V Reported CD4 levels at HIV diagnosis
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In 2004, there was a continued decreasing trend in median CD4 count among those who are aged 55 and above. The median CD4 for those who are aged less than 55 years has been stable at around 200 mark for the past 4 years (Box 1.6)
Box 1.6 ¡V CD4 Reports by age group
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Encouragingly, we continued to observe a gradually decreasing trend in the number of AIDS reports. For the very first time since 1996 (the year when HAART was introduced), we have received fewer than 50 AIDS reports in one calendar year with a figure of 49. This downward trend of reported AIDS cases remained similar to previous years with Pneumocystitis jirovechi pneumonia and Mycobacterium tuberculosis being the first and second primary AIDS defining illnesses. Forty eight (97.9%) of new AIDS patients reported in 2004 had the infection reported in no more than 3 months prior to AIDS reporting. This signifies (a) most of the AIDS patients had their HIV infection diagnosed late in the course of illness (late presenters) and (b) AIDS progression is uncommon if not of late diagnosis. Amongst all, the proportion of HIV reports with progression to AIDS within 3 months is 18% (48/268), similar to that of 2002 and 2003.
Unlinked anonymous screening and other prevalence studies yield seroprevalence data in different target populations
Seroprevalence surveys in Hong Kong cover populations with no apparent HIV risk, apparent risk and also undetermined risk. In general, the prevalence rates among tested populations have been low. The estimated HIV seroprevalence is 0.001% from a sample size of over 190 000 blood specimens at the Hong Kong Red Cross Blood Transfusion Service. A relatively high prevalence rate was found in MSM through outreach activities of a non-governmental organization. In 2004, 6 (1.8%) of 332 were tested positive whereas the figure was 0.9% in 2003. The limited coverage of the programme, however, makes interpretation difficult.
Unlinked anonymous screening (UAS) has been established as an integral part of HIV surveillance in Hong Kong following the recommendations of World Health Organization and the Scientific Committee on AIDS (SCA). It is a useful and effective tool to monitor HIV seroprevalence in community groups for which voluntary testing is constrained and serves as a first step of surveillance to a defined population. It is more acceptable to patients and vulnerable communities for fear of possible adverse consequences of HIV diagnosis, such as stigmatization.
UAS monitors HIV seroprevalence in drug users from different settings, pregnant women, elderly, prisoners and TB patients. Antenatal women and attendees of methadone clinics are good examples where UAS has worked well for a number of years before being replaced by universal HIV voluntary testing programmes. Voluntary testing programmes could facilitate clarification of HIV status at individual level for treatment and care. From 1997-2004, a total of 62588 tests were performed under various UAS programmes, which turned out 148 HIV positive tests. The annual HIV prevalence ranges from 0-0.87% in different populations. UAS in drug users from 3 different settings showed that HIV seroprevalence was <=0.6% without showing a rising trend. Prisoners could be at risk of contracting HIV because of high levels of drug use and HIV risk behaviour. Over the past 10 years, the HIV seroprevalence of newly admitted prisoners has been in the region of 0.204%-0.633% from unlinked anonymous screening, which was similar but slightly highly than that in drug users of methadone clinics and other treatment services. For details of the UAS programme, please also refer to the recent SCA publication titled "Unlinked anonymous screening for HIV surveillance in Hong Kong 1997-2004".
Universal HIV Testing programme in Methadone Clinics
Coverage of drug users has been expanded by a massive HIV testing programme introduced in methadone clinics. In last year's HIV surveillance report, a pilot universal HIV testing was performed at 3 methadone clinics. There were 9 HIV positive cases identified from 1834 tests, representing a HIV seroprevalence of 0.5%. Prior to 2004, HIV seroprevalence data are available from unlinked anonymous screening (UAS) and voluntary HIV testing in methadone clinics. For the UAS programme, the sample size of urines collected for HIV screening is between 2100-4100 samples per annum. The HIV seroprevalence ranged from 0-0.274%. The voluntary HIV testing programme at methadone clinics is not capturing an adequate number of HIV tests for meaningful interpretation. Thus, the universal testing programme using urine sample was rolled out in 2004. There were 8905 HIV tests performed on 9899 methadone clinics attendees covering all 20 methadone clinics. The coverage on the universal testing programme was 90%. According to statistics kept at Public Health Laboratory Service, a total of 18 HIV positive cases were identified from 8812 tests performed in the universal HIV testing programme. The HIV seroprevalence was estimated at 0.2% among methadone clinic attendees.
From July 2003 to December 2004, a total of 32 HIV positive cases were identified from methadone clinics. Ninety-one per cent of the HIV positive cases were Chinese and 84% of them were males. Seventy-one percent of these cases were new HIV diagnoses. The suspected route of transmission for these cases was 56% due to IDU, 22% heterosexual and 22% undetermined. The newly diagnosed patients contributed substantially to the overall reported drug-related cases during the period.
HIV remains uncommon in antenatal women
In 2004, there were no perinatal HIV cases reported. Since the launch of the universal HIV antenatal testing in Sept 2001, there were 136 052 women eligible women for HIV testing in public hospitals through December 2004. Out of whom, 132 334 women received the HIV test, which represents an opt-out rate of 2.7%. During this period, a total of 28 HIV positive pregnancies were identified; 3 cases were known before pregnancy, 24 cases were known before 23 weeks of gestation and 1 case was known after delivery. Of these 28 HIV pregnancies, 10 women underwent termination of pregnancy, 3 women were lost to follow-up, 14 women were delivered by Caesarean Section and 1 woman presented late with her HIV status diagnosed only after her vaginal delivery. At the time of writing this report, there was one baby diagnosed so far with HIV infection; 9 babies were confirmed HIV negative; 4 babies had at least one PCR test negative and one baby was lost to follow-up out of the 15 deliveries known to the system.
Level of risky drug use remained similar but sexual risk behaviours increased
Behavioural surveillance programmes have enabled the description of risk behaviours for HIV transmission in population groups over time and explores the implications of these changes in the pattern of AIDS-related behavioural markers. They have been instrumental in helping to refine public health interventions and inform the targeting of health promotion and disease control strategies. SPP Surveillance Team has been working to regularize behavioural surveillance in Hong Kong and optimise our ability to measure the impact of interventions and health promotion strategies on behaviour.
Behavioural surveillance generally aims to monitor trends in those behaviours that are amenable to change¡Xfor example, number and type of sexual partnerships, condom use, unprotected anal intercourse and sharing needles etc. Behavioural surveillance data will enable us to identify the priority areas for further in-depth epidemiological and social researches.
For the behavioural surveillance on MSM carried out at AIDS Counseling & Testing Service (ACTS) in 2004, it is observed that MSMs were not using condoms as regularly with their regular and casual sex partners when compared with previous years. Condom usage was below 20% for last sex with both regular and casual partners. There is also a slight increase on the median number of sex partner from 3 last year to 4 this year. For adult heterosexual men, regular condom use with regular partners has been maintained at around 60% and 40% attendees of ACTS and Social Hygiene Service respectively for the past few years. The figures on regular condom use are higher for commercial sex partners and stand at 80% and 70% respectively. This is a biased population as those who failed to use condoms put them at risk for HIV and STI and end up attending the aforementioned clinics. Safer sex campaigns should be organized from time to time as a health promotion strategy to increase awareness on the proper and correct use of condoms.
In terms of the behavioural risk for IDU, the figures on the proportion of injectors and the proportion of needle-sharing have largely remained stable over the past few years. Over the past year, needle-sharing activities have not become more common in any of the 3 sentinel sites in methadone clinics, drug treatment and rehabilitation centre and street addict surveys.
It is more common for street addicts to share needles than attendees of methadone clinics and drug treatment and rehabilitation centres. The proportion of needle-sharing is around 20% for the past 3 years, whereas less than 10% of those drug users attending methadone clinics and drug treatment centres admitted sharing needles.
CRF01_AE and B subtypes remain the most common HIV-1 strains
About 60% of HIV reports in 2004 had their subtypes documented in a project jointly conducted by the University of Hong Kong and the Department of Health. Of them, slightly less than one-half of the results belonged to CRF01_AE and about one-third subtypes B. There is a gradual increase in other subtypes including 08_BC, AG and 07_BC. An increase in diversity of subtypes and its recombinant forms was also noted (Box 1.7).
Box 1.7 ¡V HIV Subtypes in Hong Kong
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Ever since the first case of HIV was diagnosed in 1984, Hong Kong adopted a voluntary HIV and AIDS case reporting system. This consistent method has been used over the years, allowing fair interpretation of the temporal trend. Worldwide, differences exist in the organisation of HIV/AIDS reporting and in the type and format of information collected. There is substantial concern, supported by numerous studies, that named and mandatory reporting would deter individuals of vulnerable communities and people living with HIV/AIDS (PLHA) from seeking HIV testing and accessing care. It is vital for public health programmes to maintain a trusting and cooperative relationship with PLHA and those at greatest risk for HIV infection.
The HIV/AIDS figures reported in 2004 are largely similar to past years. Seroprevalence studies have not shown a significant rise in HIV infections among the at-risk groups or the general population. Hong Kong remains a low HIV prevalence area as suggested by the reported statistics and the various seroprevalence data so far. The HIV prevalence has been estimated to be less than 0.1% in the general population.
| HIV epidemiology 2004 at a glance |
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Over the years, sexual transmission has remained as the single most important route of HIV spread in Hong Kong. The increasing trend of MSM infection is a cause for concern. At present, there is inadequate surveillance mechanism for this vulnerable community. It is necessary to work out plans for enhancing HIV surveillance, gathering information on sexual networks, investigating possible clusters of outbreak, promotion of early HIV testing, partner counseling referral and safer sex practices in a targeted manner on MSM. Closer collaboration with non-governmental organizations and other stake holders in accessing this hard-to-reach community is necessary.
From prevention point of view, the occurrence of new HIV infections is more relevant as any of the newly reported cases may in fact be long-standing infections. Since 2001, the Integrated Treatment Centre (ITC) has been maintaining a registry to assess the dimension of recent HIV infections. In 2004, 13.6% of all new ITC attendees were documented to be recent infections within one year of diagnosis while it was 12% for the last 4-year period. Tracking new HIV incidence by epidemiologic and laboratory methods would be essential surveillance tool to supplement and complement the existing regular systems.
Molecular epidemiology is useful in enhancing the understanding of HIV epidemiology and the identification of possible clusters of outbreak. It serves to suggest epidemiological relationship of local infections, as well as linkage with those in other places. Insight can also be gained regarding the possible route of transmission and if an infection may be recent. It will be a welcome addition to HIV surveillance.
The massive public health HIV testing programmes have contributed to surveillance of and better understanding of HIV situation in targeted populations. Furthermore, early diagnosis of infected patients is achieved with prompt referral for care. Internationally, regularisation of HIV testing and improving its access in medical and non-medical settings is becoming worldwide trend. This allows better prevention, care and control of HIV/AIDS.
