What is surveillance?

Surveillance, as defined by World Health Organization (WHO) and the Centre for Disease Control and Prevention (CDC), is the "ongoing systemic collection, collation, analysis and interpretation of data, and the dissemination of information to those who need to know in order that action may be taken". It is the key component of an effective disease control programme as well as an indispensable tool for evaluation. Effective use of surveillance data on sexually transmitted infections (STIs) not only provides us with valuable information on the magnitude and trends of infections, but also the formulation of preventive intervention strategies.

The strength and weakness of the current surveillance in STIs in Hong Kong

Under the Quarantine and Prevention of Disease Ordinance (Cap 141), with the exception of hepatitis B (for which is not considered a STI because of the predominance of vertical transmission in the past), none of the commonly encountered STIs are notifiable diseases. Information concerned the local STI scenarios relies on the clinic based type of surveillance data collected by the Government Social Hygiene Service (SHS). The strength can be summarised as follows:

• Sustainable mechanism of data collection
• Responsible for caring of a substantial portion of people with STI in Hong Kong
• Clearly defined, microbiologically proven and hence reliable case definition for reporting most STIs
• Essential data on high risk behaviour leading to STIs are collected
• Data are regularly collated and reported via the publication Hong Kong STD/AIDS Update and the Virtual AIDS Office on the Internet

However, the system is not without limitations that are highlighted as below:

• Data are not population based
• Sample population is biased towards the lower social class and those symptomatic cases
  
• Under representation of the adolescence population
  
• Data on vulnerable groups are inadequately collected (such as sex workers, men who have sex with men, youth, etc.)
  
• Demographic data on individual cases are not correlated to a particular STI and therefore limit further analysis
  
• Chlamydial infection is not separately reported
  
• Errors in establishing the diagnosis of certain less prevalent and exotic infections
  
• Long term morbidity data and its impact on the health care system of STIs are not systematically collected
  
• Similar data of STI in the neighbouring countries are fragmented
  

Remedies

Given the weaknesses as stated, supplementation to these data has to be collected via different initiatives. To name a few important ones:

• Survey to STI pattern and practices to all doctors (private and public) in Hong Kong have been conducted for three times every 5 yearly
  
• Data on syphilitic serology from HKRCBTS (however, data are not properly channeled to the regular reporting system)
  
• STI/HIV related behavioural surveillance data on travelers and male adult population is collected by the academician regularly
  
• Five-yearly sexuality study of FPA has collected some useful data on the high risk behaviour of the youngsters
  

Challenges in AIDS era

In view of the close interplay between STI and HIV biologically and behaviourally, the data on STI incidence and related risk behaviour will certainly provide invaluable upland information for HIV prevention. Owing to the objectiveness and reliability of the STI data, it can be used for validation of the behavioural data collected and in addition can be used as an indicator for HIV prevention programme evaluation. The challenges are: how to put the efforts of the involved personnel together and hence better construct the local STI scenario; how to introduce the use of STI disease diagnosis to the existing behavioural data collection initiatives; convince the funding agencies that collection of information in STI is an essential part of HIV surveillance and programme evaluation; and collaboration with the neighbouring countries in collection and application of these data.