Epidemiology and surveillance

Epidemiology is the study of health and disease in populations. Disease surveillance is the ongoing, systematic collection, analysis and interpretation of health data. Disease surveillance data is used to determine the need for public health action.

During an emergency response

During a public health emergency response, epidemiology is used to understand the needs of affected populations, the nature of the disease or exposure, and to inform control activities. This can include identifying potential outbreaks or clusters of disease (through public health investigation, active case finding and contact tracing), determining causation of disease, and assessing exposure and disease risk.

Disease surveillance activities are carried out by Population and Public Health Division within the Ministry of Health and public health units within local health districts. Surveillance systems are particularly important in supporting a public health emergency response.

Health surveillance sources

Routine sources of health surveillance information include data from:

• Notifiable Conditions Information Management System (NCIMS) which collects information on conditions notifiable by laboratories, clinicians and institutions under the NSW Public Health Act 1991
• registers such as the Registry of Births, Deaths and Marriages
• Public Health Real-time Emergency Department Surveillance System (PHREDSS) which continuously monitors near real-time separation data for a number of conditions from most emergency departments across NSW, as well as ambulance dispatch data for metropolitan Sydney
• drinking and recreational water monitoring data
• reports from clinicians or institutions about unusual clusters of illness
• general practitioner influenza surveillance.

During a public health emergency response, additional monitoring and surveillance activities may include:

• hospital-based surveillance of patients admitted to hospitals and/or intensive care units with suspected or confirmed illness
• monitoring of self-reported rates of illness in the community through the NSW health survey program
• sentinel surveillance through hospitals, outpatient clinics or community-based health services
• monitoring the effectiveness of, and adverse events associated with, medications and vaccines
• actively gathering information from international and national surveillance networks and the media to monitor changes in disease and health events of interest
• monitoring health services and/or school absenteeism rates.

Maintaining close links with epidemiologists in agricultural and veterinary disease surveillance is important in promoting awareness of potential environmental hazards and supporting effective exchange of information during outbreaks of zoonotic disease.