Surveillance for acute respiratory illness that encompasses viral testing allows for tracking of influenza (flu) as well as other viruses that cause similar symptoms including those that could be newly emerging. Reports on influenza and other respiratory viruses can be found here – current week, historical (external link) , and laboratory-based virologic surveillance. (external link)
The sentinel (in selected sites around the country) surveillance systems that ESR coordinate to monitor respiratory viruses in the population are described below.
1. Hospital and Intensive Care Unit (ICU) – Hospital-based surveillance for influenza is conducted on patients admitted overnight with severe acute respiratory infections (SARI), defined by the WHO as the acute onset of cough and fever in the previous 10 days (external link) . This system was established during 2012 in the four public hospitals in central, east and south Auckland (population 906,000) as part of the Southern Hemisphere Influenza and Vaccine Effectiveness Research and Surveillance Project (SHIVERS), funded by the United States Centers for Disease Control and Prevention. All patients defined as SARI are tested for influenza and a panel of other respiratory viruses. Intensive care unit admissions defined as SARI are also monitored through this surveillance system.
2. Emergency room – Starting in 2018, emergency room (ER) visits in the Capital and Coast system (Wellington region) that are flagged as acute respiratory illnesses based International Classification of Disease (ICD) codes, are tracked. This surveillance is entirely syndromic, and therefore, does not include virologic testing. Such syndromic monitoring (external link) is now commonly used internationally as part of influenza surveillance.
3. General Practice – This surveillance is based on patients presenting to practices with acute onset of cough and fever in the previous 10 days (external link) . At the beginning of each year, 80-90 practices across New Zealand (1 practice per 50,000 residents) are recruited to participate uses electronic technology to capture. Respiratory sample for influenza and non-influenza respiratory virus testing are collected from patients with ILI symptoms bases on a defined sampling scheme - all ILIs in Auckland and Wellington and the first visit per day for the remainder of the country.
4. Healthline – Calls made to the Healthline, the free, national, 24 hour telephone health advice service funded by the Ministry of Health, are triaged using electronic clinical decision support software. Calls coded as Cold/Flu; Cough; Croup; Fever (symptom); General Aches; Headache; Sore Throat are counted as influenza-like illness (ILI). Non-symptomatic calls (30% of Healthline calls) are excluded.
Laboratory-based virologic surveillance
ESR's virology laboratory carries out year-round laboratory-based surveillance of influenza and other viruses, together with four regional laboratories. These laboratories report all virus diagnoses made, largely from hospital in-patients and outpatients, to ESR. This data is reported nationally in the ESR Virology Weekly Reports on the New Zealand Public Health Surveillance website (external link) .