Muscatello David

Surveillance of influenza epidemics is a priority for risk assessment and pandemic preparedness. Mapping epidemics can be challenging because influenza infections are incompletely ascertained, ascertainment can vary spatially, and often a denominator is not available. Rapid, more refined geographic or spatial intelligence could facilitate better preparedness and response.

Objective: Using the epidemic of influenza type A in 2016 in Australia, we demonstrated a simple but statistically sound adaptive method of automatically representing the spatial intensity and evolution of an influenza epidemic that could be applied to a laboratory surveillance count data stream that does not have a denominator.

Under-ascertainment of severe outcomes of influenza infections in administrative databases has long been recognised. After reviewing registered deaths following an influenza epidemic in 1847, William Farr, of the Registrar-General's Office, London, England, commented: ''the epidemic carried off more than 5,000 souls over and above the mortality of the season, the deaths referred to that cause [influenza] are only 1,157"[1]. Even today, studies of the population epidemiology, burden and cost of influenza frequently assume that influenza's impact on severe health outcomes reaches far beyond the number of influenza cases counted in routine clinical and administrative databases. There is little current evidence to justify the assumption that influenza is poorly identified in health databases. Using population based record linkage, we evaluated whether the assumption remains justified with modern improvements in diagnostic medicine and information systems.

Objective

To estimate the degree to which illness due to influenza is under-ascertained in administrative databases, to determine factors associated with influenza being coded or certified as a cause of death, and to estimate the proportion of coded influenza or certified influenza deaths that is laboratory confirmed.

In 2004, the NSW Public Health Real-time Emergency Department Surveillance System operating in and around Sydney, Australia signalled a large-scale increase in Emergency Department (ED) visits for gastrointestinal illness (GI). A subsequent alarming state-wide rise in institutional gastroenteritis outbreaks was also seen through conventional outbreak surveillance.

Objectives

To examine the association between short-term variation in ED visits for GI with short-term variation in institutional gastroenteritis outbreaks and thus to evaluate whether syndromic surveillance of GI through EDs provides early warning for institutional gastroenteritis outbreaks.