Surveillance in general may be defined as:
 Continuous analysis, interpretation and feedback of systematically collected data, generally using methods distinguished by their practicability, uniformity and rapidity.
It may be active or passive, and although case based in a given population, many systems, especially those doing surveillance for communicable diseases, rely on laboratory confirmation as this improves specificity of case definition. This is the system adopted by the National Institute for Communicable Diseases (NICD).
The NICD conducts laboratory-based surveillance for a number of communicable diseases. Diseases under surveillance include:

  • Epidemic-prone diseases to facilitate early outbreak identification and control e.g. meningococcal disease, typhoid, shigellosis and viral haemorrhagic fevers (VHF).

  • Vaccine-preventable diseasesto monitor the success of national vaccination programmes and guide priorities in choices of introduction of new vaccines e.g. polio, measles, Haemophilus influenzae and Streptococcus pneumoniae

  • Diseases targeted for eradication or eliminationto monitor the quality of clinical surveillance systems and to comply with international standards for surveillance e.g. polio and measles

  • Opportunistic infectionsassociated with HIV infection which may provide an indirect marker of the burden of AIDS-related infections e.g. Cryptococcus spp., S. pneumoniae and invasive Salmonella spp. infection

Although in its purist sense, surveillance may be viewed as a type of observational study to assess trends, research and other interventions often arise as a natural consequence of it. These include among others, interventions and studies relating to disease outbreaks, changes in organism serotype/genotype and changes in organism susceptibility to both vaccine prevention and antimicrobial therapy.
In the current global climate with increasing recognition of the potential for rapid international spread of emerging infections there is a growing emphasis on the importance of laboratory based surveillance in all countries. This has culminated in the adoption of the revised International Health Regulations (IHR) by the 58th World Health Assembly on May 23, 2005. These regulations outline the core capabilities required for all countries to identify and respond to health threats. The NICD therefore, by conducting surveillance aims to bring South Africa in line with these goals.