Global health. The current scenario and future perspectives

145 originated during the time of epidemiologist John Snow (1813-1858), who linked epidemiological data on cholera outbreaks in London with community interventions. According to the WHO, public health surveillance is defined as “the systematic collection, analysis, interpretation and dissemination of health data for the purpose of public health action to reduce morbidity and mortality and to improve health”. The principles of public health surveillance involve addressing a defined public health problem by using data to guide efforts that protect and promote population health. Information from various data sources can be incorporated into public health surveillance activities, such as laws and regulations or social determinants of health. One of the main components of public health surveillance is the systematic development of indicators. Other components include data collection, analysis and interpretation, and timely dissemination of findings. Additionally, the surveillance system should be capable of evaluating public health actions, including the surveillance system itself. The uses of public health surveillance data are varied and include early warning, impact assessment, development and implementation of interventions, evaluation of interventions, risk assessment, and support for public health research, among others (Choi, 2012; The World Bank, n. d.). The term epidemiological surveillance was introduced by the WHO in 1965, and it is defined as “the epidemiologic study of a disease as a dynamic process involving the ecological relationships of the infectious agent, the host, the reservoirs and the vectors, as well as the complex mechanisms involved in the spread of infection”. Some authors differentiate it from public health surveillance, arguing that epidemiology is a broader discipline that includes research and training. Others state that public health surveillance distinguishes itself by providing information to policymakers and program implementers; otherwise, it is simply health information and not surveillance information (Lee et al., n. d.). The concept of epidemiological surveillance is particularly linked to the study of communicable diseases, a term that came into use with the HIV epidemic that began in the 1980s. In 1989, the WHO developed the first standards for HIV infection surveillance. In its early years, monitoring systems were mainly limited to the reporting of HIV/AIDS cases (first- generation surveillance/passive surveillance). With this type of surveillance, information from other sources was not available, the most vulnerable or exposed groups could not be identified and changes in epidemic trends could not be explained. This led to the development of second-generation HIV surveillance (active surveillance), which allows for the analysis of different factors influencing the behavior of the epidemic, such as social, economic and cultural aspects of HIV transmission and other sexually