Review of 2007 HIV situation in Hong Kong
Adopted from HIV surveillance report - 2007 Update, SPP, CHP, DH December 2008
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HIV Surveillance at a glance (2007)
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1. The Department of Health has implemented a voluntary anonymous HIV/AIDS reporting system since 1985. The system received reports from doctors and laboratories. Medical doctors report newly diagnosed positive cases by a standard form (DH2293). In the past, only cases with Western Blot confirmed HIV antibody positive laboratory result were counted as HIV infection for cases aged above 18 months. Since the 4th quarter of 2006, cases with a PCR positive result and clinical or laboratory indication of recent infections were also counted as HIV infection in the reporting system, in view of the increasing regular detection of such cases.
2. In 2007, the department received 414 HIV reported cases and 79 AIDS reports, which increased 11.0% in HIV cases and 8.2% in AIDS cases as compared with 2006. It made the cumulative totals reached 3612 and 934 for HIV and AIDS reports respectively. 12 cases of PCR positive with clinical or laboratory indication of recent infections were included as HIV infection under the revised definition in 2006. Public hospitals/clinics/laboratories were still the commonest source of HIV reports in 2007, which accounted for over 40% of the reports. Private hospitals/clinics/laboratories were another common source of HIV reports (26.8%). Notably, the AIDS service organisations played a more significant role in HIV reporting in 2007 (6.8%). The number of reports from other sources has remained stable.
3. Over eighty percent of reported HIV cases were male. The male-to-female ratio remained at 4.8:1 in 2007. About 60% of reported cases were Chinese. Asian accounted for 16.7% of reports. The median age of reported HIV cases was 34. The age specific rate of sexually acquired infections rose in men, especially in the age group 20-24 and 25-29. Over 65% of reported cases were believed to acquire the virus through sexual transmission in 2007. Injecting drug use accounted for 10.4% of HIV infections in 2007. There was one report of HIV transmission through perinatal contact in 2007. The suspected routes of transmission were not reported in about a quarter of cases. This means that sexual transmission has accounted for 85% of HIV reports with defined risks.
4. Sexual contact was the commonest route of HIV transmission in Hong Kong. Both heterosexual and homosexual/bisexual contacts were important risk factors. In 1980s and early 1990s, the early years of AIDS epidemic in Hong Kong, it used to report more cases from men who have sex with men, including both homosexual and bisexual contacts. The trend then reversed with more heterosexual transmission reported since 1993. A rising trend in MSM has been observed since 2004. The situation was worsening this year. The number of MSM cases increased from 118 cases in 2006 to 168 cases in 2007, showing a 42.4% increase. At the same time, the number of heterosexual male cases decreased from 81 in 2006 to 68 in 2007.
5. Nearly 50% of male HIV reports this year contracted the virus through homosexual or bisexual contact. Heterosexual contact in male cases accounted for about 20%, whereas the routes of transmission were not reported in the rest 19% male cases. The ratio of heterosexual men against MSM dropped from its peak of 4.1:1 in 1998 to 0.4:1 in 2007. That meant more men were infected through homosexual/bisexual contact than heterosexual contact for consecutive three years, which was a reverse of the situation in earlier years.
Box 1.1 The number of MSM cases is taking over heterosexual men cases in the reporting system again.
6. The major attributes of the rise in MSM were Chinese and of age group 20-39. Nearly 90% of MSM cases in 2007 were Chinese. Caucasians accounted for only 8.9%. A rising trend in the number of reported Chinese MSM cases was observed in recent years. (Box 1.2) The median age of MSM cases at report was 33.5, as compared to 38 of heterosexual man cases. Age group 30-39 was the commonest age of reporting in MSM, which accounted for 44% in 2007. The HIV infected MSM population was getting younger. The median age dropped from 37 in 2005 to 33.5 in 2007. (Box 1.3) Although the rising trend in the age group of sexual active, 20-49, was observed, a prominent increase in the absolute number of cases was observed in the group 20-29. The number of cases in 20-29 43% as compared with last year. (Box 1.4)
Box 1.2 Ethnicity Breakdown of HIV-infected MSM cases
(1984-2007)
Box 1.3 Median age of HIV-infected MSM cases, heterosexual
man and heterosexual women (1984-2007)
Box 1.4 Age breakdown of HIV-infected MSM cases (1984 - 2007)
7. Only one community-based survey (PRiSM) in gay saunas, bars and clubs was been conducted in 2006 and revealed a HIV prevalence of 4.05% among MSM attending these venues. AIDS Concern's voluntary HIV testing service targeting MSM was another source to understand the prevalence in MSM although the data was affected by participant bais. A rising trend in prevalence was observed since 2004 but it seemed to be stable in recent two years. This may be affected by the expansion of AIDS Concern's service from high-risk MSM settings to general MSM populations in recent two years.
Box 1.5 HIV seroprevalence in AIDS Concern's voluntary HIV testing service
| Year | No. of blood samples | No. of samples tested anti-HIV+ | Prevalence (%) | 95% C.I. for prevalence (%) | ||
| 2000 | 38 | 0 | 0 | ( 0.000 | - | 0.000 ) |
| 2001 | 107 | 1 | 0.93 | ( 0.024 | - | 5.207 ) |
| 2002 | 130 | 1 | 0.77 | ( 0.019 | - | 4.286 ) |
| 2003 | 223 | 2 | 0.90 | ( 0.109 | - | 3.240 ) |
| 2004 | 332 | 6 | 1.81 | ( 0.663 | - | 3.934 ) |
| 2005 | 483 | 12 | 2.48 | ( 1.284 | - | 4.340 ) |
| 2006 | 610 | 10 | 1.64 | ( 0.786 | - | 3.015 ) |
| 2007 | 752 | 17 | 2.26 | ( 1.317 | - | 3.620 ) |
8. The condom use rate of MSM attending AIDS Counselling and Testing Service remained static for both regular partners and casual partners in recent years. Similar trend was observed among those attending AIDS Concern's testing service.
The number of heterosexual contact cases remained stable
9. The number of heterosexual cases remained stable in 2007. Totally 103 cases was reported, as compared with 125 cases in 2006. Because of increasing number of reported cases in other routes of transmission, the proportion accounted by heterosexual contact decreased from 33.5% in 2006 to 28.9% in 2007. The male to female ratio for heterosexual cases was 1.9:1. The median age of heterosexual cases in 2007 was 38. Heterosexual male cases were mainly (69% in year 2007) Chinese whereas Chinese only accounted for half (51% in year 2007) of female cases.
10. A majority of Social Hygiene Clinics attendees reported unprotected heterosexual contact. The seroprevalence of Social Hygiene Clinic attendees remained stable at around 0.1% (0.15% in 2007). On the other hand, the trend of sexually transmitted infections (STI) provides information for the understanding of risk of HIV infection in the community. Although it was estimated that Social Hygiene Clinics took care of only 20% of STI cases in the territory, it was still a very important sentinel site. There was a slight decrease in the total number of STI cases in Social Hygiene Clinics, an aggregate of 14,305 in 2007 as compared with 16,588 cases in 2006. A 13.8% decrease was observed in all the common STI diagnosis. The decrease of cases was more obvious in Non-specific genital infection / Non-gonococcal urethritis from 8,314 cases in 2006 to 6,761 cases in 2007.
11. The condom use rate with commercial partners remained steadily high among adult heterosexual men attending Social Hygiene Clinics and AIDS Counselling and Testing Service. The level was over 80% among those attending AIDS Counselling and Testing Service.
Small but significant numbers of infection in injecting drug users reported
12. In 2007, the reporting system recorded 43 cases of HIV transmission through injecting drug use. The number was similar to that of 2006, but at a higher level as compared with several years ago. Most of the cases were Asian, non-Chinese. The median age was 30. About 10% of injecting drug user cases was reported from methadone clinics.
13. The Universal HIV Antibody (Urine) Testing Programme replaced the unlinked anonymous screening (UAS) in methadone clinic as the seroprevalence study in 2004. 7232 urine samples were collected in the programme in 2007 with a coverage rate of 80%. The coverage of the programme was lower to that of 2006. The programme tested 14 positive cases in 2007 and with the 12 previously known positive cases still attending methadone clinics, totally there were 26 HIV positive drug users attending methadone clinic this year. The seroprevalence over the year, including the UAS period, was stable at below 1%. The seroprevalence of methadone clinic attendees in 2007 was 0.36%, which was not significantly higher than previous years.
14. Although a significant proportion of drug users were injectors, various surveys revealed that the proportion of needle sharing was relatively low. The trend remained stable over the years. The questionnaire of Street Addict Survey was revised this year and the definition of "sharing of injection equipment" included solvents and other apparatus. The trend of sharing rate in this survey had to be assessed with the data of coming years.
Cases of perinatal transmission recorded
15. In 2007, two cases reported blood contact transmission. Actually no HIV infection from local contaminated blood or blood product was found in the recent several years. The seroprevalence of new blood donors at Hong Kong Red Cross Blood Transfusion Service was at a low level of around 0.004% in 2007.
16. In 2007, one perinatal HIV infections were reported. The Universal Antenatal HIV Testing was implemented in September 2001. About 40,000 pregnant women attending public antenatal services were tested every year and the coverage of the programme reached 97.4% in 2007 and revealed the seroprevalence of HIV infection in pregnant women to be 0.02%, which is similar to that of previous years. Ten pregnant women were tested positive in the programme this year. No woman terminated their pregnancy and nine women delivered their babies by Caesarean Section. The rest gave birth by vaginal delivery.
Cases with undetermined risk factor on the increase
17. The information of voluntary reporting was becoming incomplete as there are an increasing proportion of cases reported without a risk factor. Similar to last year, nearly a quarter of cases reported without a suspected route of transmission. These cases were usually those without a physician's reporting. Undetermined risk is commoner in cases reported by private hospitals/clinics/laboratories. Although this was a voluntary reporting system, physicians were strongly encouraged to make the system be comprehensive. The data could be useful for a better understanding of the local HIV epidemiology.
Pneumocystis Pneumonia and Tuberculosis were common Primary AIDS Defining Illness
18. The annual number of reported AIDS cases was dropping since 1997, the year of introducing highly active antiretroviral therapy (HAART) in Hong Kong but a slow increasing trend was observed recently. Seventy-nine AIDS cases were reported as compared with 73 cases in 2006. The rate of increase was comparable with that of HIV cases. 50 cases (63.3%) of the AIDS reports this year has their AIDS reported within 3 months of HIV reporting.
19. The primary AIDS defining illness (ADI) pattern of the reported cases also changed slightly in recent years. Pneumocystis jirovechi pneumonia (previously named Pneumocystis carinii) has been the commonest ADI in Hong Kong. This year, 32 cases reported Mycobacterium tuberculosis as the primary ADI. Mycobacterium tuberculosis was taking over again as the commonest ADI. Pneumocystis pneumonia was the second commonest ADI, which accounted for 28 cases (35.4%). They were followed by Penicilliosis (4, 5.1%), and other Cytomegalovirus diseases (4, 5.1%). On the other hand, unlinked anonymous testing in tuberculosis patients demonstrated a seroprevalence of 1.240% in 2007. An increasing trend was showed and stayed at a relatively high level since 2002. This figure was even higher than that of Methadone Clinic attendees and Social Hygiene Clinic attendees.
20. The median CD4 of newly reported HIV cases in 2007 was 216.5. Reporting of CD4 level was becoming a routine practice in physician. It provided useful information on the timing of diagnosis in the course of HIV infection. 61.4% of HIV cases in 2007 reported the CD4 level at diagnosis. The median CD4 for those aged less than 55 has been stable at around 200 (196 - 238) for the past 5 years. One the other hand, there was a continued decreasing trend in median CD4 count among those who are aged 55 and above. It suggested that more patients reported at age 55 or above were diagnosed at a late disease stage. (Box 1.6 & 1.7)
Box 1.6 - Reported CD4 levels at HIV diagnosis
| Year | No. of HIV reports | No. of CD4 reports (%) |
Median CD4 (cell/ul) |
CD4>=200 (cell/ul) (%) |
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| 2001 | 213 | 162 | ( 76.1% ) | 233.5 | 85 | ( 52.5% ) |
| 2002 | 260 | 201 | ( 77.3% ) | 197 | 100 | ( 49.8% ) |
| 2003 | 229 | 166 | ( 72.5% ) | 205 | 85 | ( 51.2% ) |
| 2004 | 268 | 177 | ( 66.0% ) | 215 | 95 | ( 53.7% ) |
| 2005 | 313 | 211 | ( 67.4% ) | 198 | 105 | ( 49.8% ) |
| 2006 | 373 | 252 | ( 67.6% ) | 209 | 133 | ( 52.8% ) |
| 2007 | 414 | 254 | ( 61.4% ) | 216.5 | 137 | ( 53.9% ) |
Box 1.7 - CD4 Reports by age group
| Age | Year | No. of HIV reports | No. of CD4 reports (%) | Median CD4 (cell/ul) | % of CD4 >= 200 (cell/ul) | |
| <55 | 2001 | 190 | 146 | (76.8%) | 258.5 | 54.1% |
| 2002 | 230 | 183 | (79.6%) | 196 | 49.7% | |
| 2003 | 190 | 139 | (73.2%) | 228 | 52.5% | |
| 2004 | 225 | 156 | (69.3%) | 226.5 | 56.4% | |
| 2005 | 280 | 188 | (67.1%) | 197 | 49.5% | |
| 2006 | 339 | 228 | (67.3%) | 234.5 | 55.7% | |
| 2007 | 378 | 236 | (62.4%) | 238 | 55.1% | |
| >=55 | 2001 | 22 | 16 | (72.7%) | 96 | 37.5% |
| 2002 | 24 | 18 | (75.0%) | 212.5 | 50.0% | |
| 2003 | 32 | 27 | (84.4%) | 108 | 44.4% | |
| 2004 | 32 | 21 | (65.6%) | 82 | 33.3% | |
| 2005 | 29 | 23 | (79.3%) | 223 | 52.2% | |
| 2006 | 28 | 23 | (82.1%) | 145 | 21.7% | |
| 2007 | 32 | 18 | (56.3%) | 97 | 38.9% | |
The commonest HIV subtypes were CRF01_AE and B
21. In 2007, about 80% of HIV reports had their subtypes documented. CRF01_AE and Subtype B of HIV-1 strains were the most common subtypes identified in Hong Kong. They together accounted for 78.0% of all HIV cases. CRF_01AE was found to be commoner in female, Asians non-Chinese, heterosexuals and IDU. The subtype B was commoner in Caucasian, MSM and C subtypes in females, Asians and sexually transmitted cases. An increasing diversity of subtypes and its circulating recombinant forms was also noted. (Box 1.8)
Box 1.8 - HIV Subtypes in Hong Kong
| 2002 | 2003 | 2004 | 2005 | 2006 | 2007 | |||||||
| Annual HIV Reports | 260 | 229 | 268 | 313 | 373 | 414 | ||||||
| No of reports with subtypes (%) | 228 | (88%) | 204 | (89%) | 202 | (75%) | 258 | (82%) | 315 | (84%) | 364 | (88%) |
| Subtype (%) | ¡@¡@¡@¡@¡@¡@ | |||||||||||
| CRF01_AE | 122 | (47%) | 99 | (43%) | 95 | (35%) | 125 | (40%) | 149 | (40%) | 164 | (40%) |
| B | 78 | (30%) | 60 | (26%) | 71 | (26%) | 101 | (32%) | 124 | (33%) | 159 | (38%) |
| CRF08_BC | 1 | (0%) | 4 | (2%) | 10 | (4%) | 6 | (2%) | 11 | (3%) | 14 | (3%) |
| C | 15 | (6%) | 21 | (9%) | 3 | (1%) | 2 | (1%) | 6 | (2%) | 2 | (0%) |
| Others | 12 | (5%) | 20 | (9%) | 23 | (9%) | 24 | (8%) | 25 | (7%) | 25 | (6%) |
Discussion
22. The number of HIV reports was persistently on a rise in 2007. The annual HIV reports used to be around 300. The total number of HIV reports in 2007 was 414, which was an 11% increase as compared to 2006. In the previous five years, there was 10-20% increase in HIV reports every year except in 2003, when SARS outbreak occurred. The rise this year was mainly contributed by increasing reports from Men who have Sex with Men. An increase in injecting drug users was observed but mainly in non-Chinese population, which suggested non-local infections.
23. The number of HIV reports among MSM continued to rise and it accounted for even a larger proportion this year. The HIV situation in MSM was really worrisome because the increasing trend has persisted and in an escalating fashion. The young MSM aged 20-29 was heavily affected. The community-based seroprevalence survey in 2006 revealed a high HIV prevalence. Both condom usage rates of MSM with casual and regular partners remained at a lower level than that of heterosexual men visiting sex workers. Reporting data, prevalence data and behavioural data all suggested a persisting local HIV epidemic in MSM.
24. Heterosexual transmission appeared to be in a stable trend over the years. A significant proportion of non Chinese cases suggested infections outside Hong Kong. For heterosexual men, only 33.3% of their contacts were believed to have occurred in Hong Kong. The prevalence in social hygiene clinics attendees and antenatal women were all below 1%. The condom use rates of commercial sex were high on both from the report of sex workers and their clients.
25. Although the number of HIV-infected injecting drug users was persistent at a high level, an escalating growth of HIV infections in injecting drug users was not expected at present. Same as last year, most reported injecting drug users were Asian non-Chinese. It was believed that those non-Chinese acquired the infection outside Hong Kong. The number of HIV infections in drug users contributed by the local infections was not largely different from previous years.
26. In conclusion, the HIV infections in Hong Kong were increasing and mainly affecting MSM populations. The situation of heterosexual population and local injecting drug user population was stable. The HIV epidemiology in Hong Kong was also affected the situation of neighbouring countries. A proportion of cases were infections which acquired outside Hong Kong.
