Table 1 Aims and requirements for HAI and SARI surveillance

Aims of surveillance

Provide insight into infectious complication of medical care to initiate or evaluate preventive interventions; timely detection of increased rates of HAI, possibly related to breaches in infection control

Monitor epidemiologic trends and characteristics and impact of SARI on healthcare facility utilization and mortality

Early detection of outbreaks of known or unknown pathogens

Evaluate public health interventions such as vaccination and monitor vaccine effectiveness

Identify risk factors for SARI

Numerator, case definition

Standardized case-definitions, usually including microbiological testing outcomes with clinical signs and symptoms

Syndromic case-definitions either fulfilling the WHO case definition for SARI or a proxy case-definition. Ideally complemented with causative pathogens

Denominator

Patient days at risk, device-days at risk or number of procedures

General population or catchment population of participating centres

Large-scale uniformity of case definition and case ascertainment

Important, for assessing local performance against comparators in time or place

Important for comparisons between countries or catchment populations and comparisons in time

Reliable over time

Very important, to detect changes in relatively rare outcomes

Important to detect small changes due to emerging pathogens

Timeliness

Less important, retrospective by design

Very important for the aim of early detection to guide control measures for epidemics

Risk adjustment

Important, for assessing local performance against comparators in time or place

Important for emerging pathogens to identify risk groups and to adjust for differences in catchment populations on a national level