NSW has had success in controlling COVID-19 related illness – this far in 2020, and surveillance mechanisms for COVID-19 are well established in NSW. Actively identifying newly infected people and their close contacts have been essential to this success.
NSW maintains high rates of testing and low test positivity.
NSW has taken an aggressive approach to stem the number of cases associated with each outbreak and has tightened restrictions preventing the number of people able to attend public places. NSW continues to monitor the impact of the recent relaxation of public health restrictions through enhanced surveillance.
The existing activities that provide the foundations for surveillance and will be part of the public health response for the duration of the pandemic include:
This plan describes the enhanced surveillance activities that will be performed in NSW to support the public health response to COVID-19. This plan is closely aligned to the Australian National Disease Surveillance Plan for COVID-19, which in turn supports the Coronavirus (COVID-19) in Australia – Pandemic Health Intelligence Plan.
The COVID-19 enhanced surveillance goals for NSW are to:
This plan describes the NSW approach to surveillance for COVID-19, and the virus that causes it, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
Surveillance is the ongoing, systematic collection, analysis and interpretation of health- related data. Surveillance data collected as part of the plan will inform the public health response to COVID-19 in NSW, through timely reporting and description of cases and clusters, testing patterns, community transmission patterns and the outcomes and severity of illness.
Surveillance in NSW is a partnership between state government agencies, health research institutions, public and private laboratories, and other health sector stakeholders. The plan recognises and builds on established systems for communicable disease surveillance in Australia.
The NSW Public Health Response Branch (PHRB) is responsible for the plan and monitors its implementation. The plan is a living document that will be regularly updated as surveillance priorities and needs change, to support responses proportionate to the level of risk over time, geographic regions and for different population groups. The plan will be responsive to the needs of the Crisis Cabinet and the State Pandemic Emergency Management Committee. Principles underlying the development and implementation of the plan are at Appendix 1.
NSW has a well-established case based surveillance system which relies on reporting from public health units, which in turn depend on reports from laboratories, health facilities and medical practitioners. This system is used to report at state and national level on all new diagnoses of infection with SARS-CoV-2. It is also used to report at state and national level on testing for COVID-19.
The ability to detect cases of SARS-CoV-2 infection is central to the strategies used to prevent transmission in Australia. A high rate of well-targeted testing is essential to provide confidence that cases will be detected as control measures evolve. A testing framework for COVID-19 in NSW has been developed as a companion to this plan (Appendix 2). The testing framework outlines the settings in which testing is currently being conducted or proposed to be conducted for COVID-19, and emphasises that the highest priority group for testing is people with symptoms.
Australia has a number of established surveillance systems originally set up to monitor influenza and influenza-like illnesses and their complications. These systems include syndromic surveillance, where data are collected based on the clinical features of people without a diagnosis, and sentinel surveillance, involving selected health facilities that collect high-quality data that cannot be obtained through case-based reporting. There are also mechanisms for reporting on health service utilisation and outcomes for people admitted to tertiary care with COVID-19. The data collected will be used to signal trends and monitor the burden of disease in the community.
Serosurveillance complements the understanding of population transmission of SARS-CoV-2 obtained from case-based reporting, which largely misses asymptomatic, mild or atypical cases and those that do not present to health care or are not tested when ill. It helps us understand at a population level how many people have been infected. This information will support epidemic modelling and may provide an indication of population immunity in future, noting the uncertainties around its interpretation and the need to understand the level of sero-reversion in the community and its implications
The incorporation of viral genomic data into epidemiological surveillance can clarify the likely source of infection in outbreak settings or in cases arising without a known source, and support characterisation of clusters and patterns of community transmission. It can also be used to monitor SARS-CoV-2 evolution to identify whether different virus variants are emerging over time, and if there is any impact to the accuracy of diagnostic tests or change in pathogenicity, immunogenicity, or transmissibility.
Each surveillance goal contributes information to help national, state and territory public health authorities better understand the pattern and frequency of COVID-19 infection and factors (such as age) associated with infection. Data are used to assess and inform public health measures. Each goal is measured and monitored through one or more indicators.
Indicators
Data collected on all laboratory confirmed cases of COVID-19 are used to characterise the epidemic by person, place and time. This epidemiological information is critical to assess the effectiveness of public health measures and inform targeted approaches.
Daily number, and weekly rate (case fatality and per 100,000 population) of deaths in people with COVID-19 by demographic characteristics
The number and rate of COVID-19 related deaths is an indication of the scale of the epidemic and the severity of infection, and can indicate whether these factors are changing over time. Mortality data identifies population groups most at risk while informing public health measures to protect them; and may provide insight into the performance of the health care system.
The daily number of tests for SARS-CoV-2 conducted and the proportion that are positive are metrics used to better interpret case-based data. These data provide the uptake of testing in different populations, locations and time periods and are used to assess future need for testing related equipment, consumables and staff resources. Testing data is an important measure to indicate that the key disease control strategies of case isolation and contact quarantine can be effective.
Work closely with the Commonwealth to use the data available from the COVIDsafe app to improve public health contact tracing efficiency and completeness. An evaluation of this activity is in development.
People in close contact with a confirmed or probable case of COVID-19 are at higher risk of contracting an infection with SARS-CoV-2. Rapid identification and quarantining of close contacts of cases through contact tracing helps break chains of transmission by ensuring that contacts do not transmit the virus to any other people. For cases with no known source of transmission, contact tracing back through the time that the case would have acquired their infection may also identify previously undiagnosed cases in the community. Contact tracing data can contribute to knowledge transmission dynamics for SARS-Cov-2. In addition, these data provide a measure of public health effectiveness in undertaking contact tracing in a timely way.
Effective contact tracing also relies on the public health objectives of early diagnosis (people with symptoms isolating themselves and presenting for testing soon after symptom onset, and accessible and rapid laboratory testing and reporting) (indicators 1 and 2 above).
For effective suppression of COVID-19, it is important to rapidly identify and control clusters particularly in high-risk settings such as residential care and healthcare facilities.
Characterisation of clusters and secondary cases can inform targeted strategies to prevent further outbreaks.
Our current understanding of COVID-19 is that approximately 80% of infections result in mild illness 1; the most common symptoms are similar to those of other acute respiratory illnesses. Information on clusters, outbreaks and other broad patterns of community transmission when viewed together with data from other surveillance indicators paints a more complete picture of the scale and impact of the epidemic, and the effectiveness of public health measures.
Describing the number and characteristics of hospitalised COVID-19 cases gives an indication of the extent of infection in the community, the severity of illness and whether these factors are changing over time. These indicators identify high-risk groups for severe illness or complications due SARS-CoV-2 infection to inform targeted public health measures. These data also inform resource allocation requirements to ensure safe, timely and quality health care.
Hospital capacity and activity data, when collected over time, can be used to forecast resource requirements and allocation.
Antibody prevalence to SARS-CoV-2 by age group, sex, geographic area, risk group (e.g. by age, health care workers, Indigenous people) and over time (during and after epidemic peaks).
Conduct a population-based serosurvey to determine the prevalence of previous SARS- CoV-2 infection in pregnant women, routine blood donors, and other people who have had blood collected for monitoring of their health condition.
Infection with SARS-CoV-2 can result in mild, asymptomatic or atypical illness which may not be detected by standard surveillance systems. Serological testing for surveillance can indicate how widely SARS-CoV-2 infection has spread across the general population and within specific groups. It should be noted that serological surveillance does not tell us if or for how long antibodies protect people against re-infection.
Number and proportion positive for SARS-CoV-2 of asymptomatic cases in structured, systematically designed studies of populations at high-risk, and/or settings in which repeatable cross-sectional sampling is feasible.
Asymptomatic testing is an active surveillance measure that seeks to uncover undetected infection in outbreak situations or high risk settings. This indicator contributes to the broader knowledge base on virus characteristics and provides a greater understanding of the extent of virus circulation in the community.
The ability to detect cases of COVID-19 is central to the strategies that can be used to prevent ongoing community transmission in NSW. A high testing rate across the population, and particularly in populations that are more likely to have infection due to symptoms or epidemiological links is essential to provide confidence that cases will be detected as control measures are adjusted.
This framework for testing for COVID-19 in NSW supports this plan, and also supports the Australian National Disease Surveillance Plan for COVID-19, which has the tracking of testing rates among its key components. It outlines the range of surveillance activities that track routine testing, or introduce additional testing for surveillance purposes, for COVID-19.
It is important that surveillance and testing are prioritised to meet the key public health objectives of minimising transmission. Detection of infections, their contacts and outbreaks is currently conducted through testing in symptomatic people, followed by comprehensive contact tracing around every case. This strategy must be maintained and enhanced as the highest priority, ensuring that all people who develop symptoms consistent with COVID-19, are tested. This is the most important and effective testing, providing direct public health results.
To increase testing coverage, the Communicable Diseases Network Australia (CDNA) expanded its recommendations for testing from 22 June 2020 to anyone with Acute Respiratory Infection (ARI) or fever (≥37.5°C) or history of fever or loss of smell or loss of taste, where no other clinical focus of infection or alternate explanation of the patient's illness is evident. The uptake for this is yet to be evaluated.
Surveillance based on FluTracking for the week ending 26 April 2020 indicated that only one third of people with fever and cough were tested for COVID-19. There is added difficulty in increasing testing numbers when acute respiratory illness and influenza-like illness rates are markedly decreasing owing to the current physical distancing measures. To be confident there is high case ascertainment, the amount of testing should reflect the prevalence of acute respiratory illness in the community. This can only be achieved by effective communication to the public, and removal of barriers to testing to ensure all symptomatic people are tested, including marginalised populations, those with limited access to healthcare and those who may have a disincentive to be tested. This alone would greatly increase the number of tests conducted in Australia. As physical distancing measures are lifted and other respiratory viruses again circulate at a higher level in the community testing all people with ARI will further increase the COVID-19 testing rate.
In addition to testing all symptomatic people, testing should also expand to asymptomatic people in settings of outbreaks, such as might occur in health care or aged care settings, and in vulnerable populations or remote and isolated communities. This can provide early detection of cases and information of asymptomatic people. Serology testing is also of value, both for population surveys to estimate how far infection has spread, and for upstream contacts of cases with no epidemiological link to identify sources of infection. The use of whole genome sequencing, which can demonstrate links between cases, may also be effective in these scenarios.
The incidence and significance of asymptomatic cases is not well understood. Most of Australia currently has very low COVID-19 incidence. At present the CDNA and the Australian Health Protection Principal Committee therefore do not recommend systematic, ongoing testing of asymptomatic people. Mathematical modelling shows that testing of unselected asymptomatic individuals is not an effective way of detecting community transmission compared with enhanced testing in symptomatic cases, and contacts of cases. Such testing would use significant testing resources and the effect of potential false positive results needs to be considered. Asymptomatic people may also choose not to be tested. Nevertheless, there may be a situation in which time-limited surveys of asymptomatic people may be of value, particularly in outbreak situations or in high risk settings such as health care or residential aged care facilities or in vulnerable populations.
Serosurveys measure the prevalence of antibodies to SARS-CoV-2, which in most people appear by around 12–14 days after initial infection, whether or not the person had symptoms of illness, and may remain detectable for several months or longer.
Serosurveillance complements epidemiological data collected using case reporting based on detection of the virus, which is likely to miss infections that are asymptomatic, mild or atypical or are not tested during the acute phase of their illness. Serosurveys provide a better understanding at the community level, of how many people have been infected with the virus, and are considered an essential piece of pandemic intelligence. However, currently serosurveillance cannot be used to measure population immunity, because the extent to which antibodies can protect against future infection is not known.
Serosurveys conducted in NSW will be designed to examine variation in seroprevalence by geographic location, age group, sex, and population group. Populations that will be examined include the general population, pregnant women and blood donors.
The preferred approach for monitoring seroprevalence in NSW and Australia is through testing of anonymised residual blood specimens routinely collected for other purposes for the presence of SARS-CoV-2 antibodies. Using this approach, samples are selected using repeatable methodologies, to broadly reflect the desired population distribution. Analyses of these samples can be assumed to be reflective of time trends and geographic patterns in SARS-CoV-2 infection rates in the underlying communities from which they are drawn.
Targeted serosurveillance supplements data from residual specimen collections described under Objective 1, but also addresses specific questions around infection risk, severity of illness and outcomes (if paired with clinical data) among key populations of interest. These surveys involve proactive blood specimen collection. Specific populations of interest include children and adolescents who have less routine blood testing, as well as high-risk populations such as the elderly and health care workers. Serosurveillance in younger age groups may be undertaken through active recruitment of consenting participants in emergency departments, health care facilities, residential aged care facilities or schools.
Approval to conduct serosurveillance to support the public health investigation into COVID- 19 has been obtained under the Public Health Act 2010. This serosurveillance will be conducted in NSW as a collaboration between the National Centre for Immunisation Research and Surveillance (NCIRS), the Kirby Institute, NSW Health Pathology. It will be funded by the NSW Ministry of Health.
Prevalence of past or recent infection (as demonstrated by the presence of antibodies to SARS-CoV-2) by geographic area, age group, time, and in key populations, reported to the NSW Ministry of Health and made available to mathematical modellers and others who will appropriately use data.
