HIV Surveillance and Epidemiology

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Seroepidemiology of HIV infection is determined in communities with predisposing risk factors and communities without risk factors. Surveillance methodology includes both voluntary HIV testing [1] and unlinked anonymous screening [2].

The following table summarises the programmes under the Serosurveillance system : -

Target population

Setting

System

Since

Sample size

(a) community with predisposing risk factors

Patients with sexual transmitted infection Social Hygiene Clinics Voluntary testing offered to clients 1985 26000 in 2015
Drug users (1) Methadone Clinics Unlinked anonymous screening (Urine samples) 1992 (to 2003) 2000 - 4000 / year
Universal HIV Antibody (Urine samples) Testing Programme 2003 6000 in 2015
Drug users (2) Inpatient drug treatmet centres/institution Unlinked anonymous screening (Urine samples) 1998 350 in 2015
Drug users (3) Street drug users approached by outreach workers Unlinked Anonymous Voluntary testing (saliva samples) 1993 (to 1997) 200 - 500 / year
Men who have Sex with Men (MSM) AIDS Concern Voluntary testing offered to MSM (rapid tests) 2000 250000 in 2015
HIV Prevalence and Risk behavioural Survey of Men who have sex with men in Hong Kong(PRISM) Unlinked anonymous screening (urine samples) 2006 round 800 / study
Voluntary testing (urine samples) 2008, 2011 round 800/study
Female Sex Worker (FSW) Community Based Risk Behavioral and Seroprevalence Survey for Female Sex Workers in Hong Kong (CRISP) Unlinked anonymous screening (urine samples) 2006 round 900/study
Voluntary testing (urine samples) 2008 round 900/study

(b) Community without known risk factors

Blood donors

Hong Kong Red Cross Blood Transfusion Service

A requirement to all potential donors

1985

250000 in 2015

Antenatal women All maternal and child health centres and public hospitals Universal voluntary testing (blood samples) Sept 2001 50000 in 2015

Pregnant women having deliveries in hospital

Testing of Cord blood from delivery women at labour wards

Unlinked anonymous screening (blood samples)

1990 (to 2000)

4000 / year

Civil servants

Pre-employment health check

Unlinked anonymous screening (blood samples)

1991 (once)

1553

(c) Community with undefined risk

TB patients (1)

TB and Chest Clinics of the Department of Health

Unlinked anonymous screening (blood/urine samples)

1990 (to 2008)

1000 / year

TB patients (2)

TB and Chest Clinics of the Department of Health

Voluntary testing (blood samples)

1993

3300 in 2015

Prisoners

Penal institutions

Unlinked anonymous screening (urine samples)

1992

1500 in 2015

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[1] Voluntary HIV Testing

While case-based surveillance took on a headstart, it alone was inadequate for describing the epidemiology of HIV infection. When HIV tests became widely available in 1985, seroprevalence studies were performed to complement the results of voluntary reporting.

The HIV positivity rates in three population subgroups constitute the database for HIV seroprevalence studies since 1985. They are clients attending the Social Hygiene Services, drug users of Methadone treatment programmes and blood donors. The former two groups are the results of voluntary testing. As for blood donors, while the donation of blood is voluntary and non-paid, HIV screening is universal to all collected blood units. HIV test universally offered to all clients of the STD clinic.

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[2] Unlinked anonymous screening studies (UAS)

Unlinked anonymous screening (UAS) was started in 1990 in line with WHO recommendation adopted by the Scientific Working Group on AIDS. The essential characteristics of UAS are : (a) specimens for UAS are taken from those for other purposes for which consent have been obtained, (b) personal identifying particulars are removed prior to submission for testing, and (c) there is no possible way of tracing back the results to individuals person. Since 1990, unlinked anonymous screening has been undertaken in Hong Kong to determine HIV prevalence in selected groups so as to facilitate design, implementation and monitoring of public health programmes for the prevention, control and care of HIV infection and AIDS.

Based on the principles proposed by the WHO and the local Scientific Committee on AIDS, UAS has covered two categories of populations : (i) people vulnerable to HIV due to their behaviours, and (ii) those without apparent risk behaviours and are supposingly at lower or general risk. The former includes drug users attending the methadone clinics, street drug users, and correctional institute inmates while the latter group comprises patients with tuberculosis, pregnant women having deliveries in hospitals and male government recruits. Apart form blood, urine and saliva specimens have been employed for this purpose, depending on the specific setting of specimen collection for individual target groups.

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