4. Surveillance Principles

Updated 1 October 2025
Core Principle
 
The Health Surveillance System in principle protects the population from different health risks or diseases, by detecting any health-related problem that can cause an Acute Public Health Event that requires an immediate and integrated response. It also serves to develop prevention, and control programs that promote health and wellbeing within the population.
  • A key principle is to include only conditions for which surveillance can effectively lead to prevention.
  • Health problems under surveillance are analyzed in association with their possible causes or determinants and in a close relation between humans, the environment, animal health (One Health), and the possible interventions for prevention and control, under an intersectoral and community approach.
  • After the updates of the IHR (2005), the epidemics of the XXI Century and other Public Health Emergencies of National or International Concern, surveillance has included as a principle that “its scope is not limited to any specific disease or manner of transmission, but covering illness or medical condition, irrespective of origin or source, that presents or could present significant harm to humans”.
  • The Health Surveillance System is based primarily on the Health Care Facilities (outpatients, emergency services and hospitalized patients), labs and environment but also includes the professionals that provide private and public health services to the community and field work, investigation, preventive activities, and those sharing information with the Animal Health Sector.
  • The complexity and diversity of different sources of data collection, from individuals and aggregate data, data transmission, processing, and analysis, using multiple complex techniques and producing timely responses have created the necessity to migrate to, and use, electronic surveillance, or information systems with capacity to manage the subsystems, and the whole information from the inputs, process and analysis, and outputs.
  • Surveillance systems have a general structure and subsystems because there are areas of the public health related to specialized programs, for example, syndromic and lab surveillance, Tuberculosis (TB) and Human Immunodeficiency Virus / Sexually Transmitted Infection (HIV/STI) or NCD/MH – Non-communicable diseases / Mental Health (NCD/MH), that are complementary, and at the same time, integrated in the epidemiological analysis and response at different levels.
  • Surveillance is based on epidemiological categories: health-related states or events (what), persons (who), place (where), time (when), and causes, risk factors, and modes of transmission (why/how), health promotion and disease prevention