Data notes

By Juliette O'Brien

May 1, 2020

The context in which this data is being collected and documented is unique. We are attempting to track in as timely a manner as possible an unfolding epidemic in which information is limited. Australia’s federal system means separate jurisdictions take responsibility for healthcare and report it in different ways. At times, discretion and adaptation have been required. We’ve tried to document these below.

We are grateful to collaborators and especially readers for the many pieces of feedback and advice that have helped with information and decision-making. If you would like to send a comment or request, please get in touch.



Notes on new daily cases vs net daily cases [Data downloads available]

Summary: The number of new cases each day may differ from the net number of cases added to the total. The Daily briefing on the homepage shows new cases and net added cases in brackets. e.g. 7(+4) = 7 new cases, but only 4 added to the total because 3 previous cases were removed. Epicurves on the site show new cases. For net cases, use the links below.

Several scenarios have led this site to track new daily cases and net daily cases separately. For example, cases are occasionally moved between jurisdictions to comply with national reporting standards that require reporting based on residency rather than locality. This causes cumulative totals to be adjusted upwards or downwards depending on whether the state or territory is sending or receiving the case/s. (In the past, they did not always announce these types of cases explicitly; they simply made adjustments to the running totals). Downward adjustments may also occur after cases have been ruled out following further investigation or false positive results. Another scenario that is increasingly frequent is the confirmation of ‘historical’ cases following serology testing. This is slightly different from the other situations because these cases do still represent new additions to Australia’s case numbers, however they are not ‘new’ cases in an active sense.

To help make sense of these daily announcements and adjustments, this site tracks new daily cases and net daily cases separately. The goal is to make sure we can see how many new ‘active’ cases there are, separately from historical cases or technical adjustments.

Other sites tracking COVID-19 cases in Australia usually track net cases added. i.e. Daily cases are calculated by subtracting yesterday’s total from today’s. Previously this site took that approach also, however it changed policy with respect to downward adjustments as of 15 April 2020, upward adjustments as of 12 May 2020 and newly confirmed ‘historical’ cases on 17 May 2020. These changes in policy have resulted in some retrospective changes to the epicurve which have been documented below via the charts that show the difference between new confirmed and net added cases.

While the main epicurve, which is on the homepage and states and territories page, shows new daily confirmed cases that are announced by states and territories, this collection of charts is designed to give the full picture of Australia’s daily confirmed cases of COVID-19. Data is updated live and downloadable by clicking the download icon in the bottom left-hand corner of each chart.

1. New daily confirmed cases (i.e. new confirmed cases as announced). 

  • View and download national data here.​

  • View and download state and territory data here.

2.  Net daily added cases (i.e. cases added to reach announced total).

  • View and download national data here.​

  • View and download state and territory data here.​

3. Difference between new confirmed and net added cases

(Also shows revisions to the epicurve that come out of the changes in approach).

  • View and download national data here.​

  • View and download state and territory data here.​​

4. Cumulative total of confirmed cases.

  • View and download national data here.​

  • View and download state and territory data here.​

Notes on confirmed cases and deaths

  • Cases and deaths are recorded on the day they are announced or published to the public. For all states and territories except Tasmania, this means cases recorded on today’s date reflect the previous day’s reporting period. Tasmania is the exception because it reports in the evening cases from the current day, not the previous day. Therefore, while it appears on this site that Tasmania is the last state to report, it is in fact the first, as its figures refer to a reporting period one day ahead of the other states.

  • 2 Queenslanders who died in NSW are reported in Queensland figures.
  • At least 2 overseas tourists (non-residents) who died in Western Australia have been included.

  • 20 March 2020: NSW brought its reporting time forward, creating a lower than usual figure for that day.

  • 6 April 2020: 1 Northern Territory case was removed due to double-count with NSW. (Action taken 1 May 2020).

  • There are ongoing discrepancies between the cumulative total number of confirmed cases as reported by individual states and territories compared with those reported by the federal government. This site currently reconciles with federal figures. The federal government reports cases according to residency while states and territories generally report cases located within their jurisdictions. Corrections and adjustments to the running totals are frequent and generally ensure state and territory figures align with federal figures. Additionally, as of 23 May 2020, the federal government has not added ‘historical’ cases to the total, citing them as probably only. The current and ongoing discrepancies are:

    • Northern Territory reports +1 (due to residency)

    • Tasmania reports -2 (due to residency)

  • Running totals of confirmed cases may be adjusted upwards or downwards outside of announced confirmed cases. Please see the section above (new daily cases vs net daily cases) for details.

  • Interstate transfers: where a state announces ‘new’ cases but verbally specifies that some are ‘old’ due to interstate transfers, the old cases will not be added to the ‘new’ epicurve, but added only to the net daily additional cases.

  • Historical cases following serology testing: where a state announces new historical cases following serology testing, these cases will not be added to the ‘new’ epicurve, but added only to the net daily additional cases. Note – 3 such cases in WA on 16 and 17 May 2020  were originally added to new daily cases but have been moved to net cases only.

  • 16 May 2020: 2 ‘historical’ cases were confirmed in Western Australia. These were added to net daily cases, not new daily cases, however federal figures revised WA figures down by 1, therefore only 1 net case was added.

  • 18 May 2020: The federal government added +3 net cases for both Victoria and Western Australia in order to reconcile cumulative totals. The originating dates of these cases are not clear, but based on previous downward adjustments that had caused the totals reported by the federal government to diverge from those reported by the states, the cases are likely to be: +2 on 12 May and +1 on 14 May for Victoria:, and +2 on 13 May and +1 on 16 May for Western Australia. Cases that had previously been removed from the net cases on these days have been reinstated.

  • 23 May 2020: Federal figures released by the Department of Health did not add new cases to Western Australia (+3) or Queensland (+2), leading to a total national figure of -5. This site generally reconciles with federal figures at the end of each day. Today however, federal figures are irreconcilable with remaining active cases in Western Australia and Queensland. Therefore this site currently reflects the totals as reported by the states, rather than the federal government.

Notes on active cases and recoveries

  • Before 5 April 2020, not all states and territories reported recoveries. The federal Department of Health began publishing recoveries on this date which created a jump for some jurisdictions.

  • States and territories are responsible for reporting recoveries and active cases. The sum of active cases, recoveries and deaths does not reconcile with the total number of cases. This site reflects the collection of state and territory announcements with the following adjustments:

    • As noted above, Tasmania reports -2 confirmed cases compared with federal figures. This site has included these cases in Tasmania’s cumulative total (in order to reconcile with federal figures) but to date, has not included them in Tasmania’s recoveries or active cases. This is in order to align with the figures Tasmania reports.

    • 2 deaths double-counted by Queensland and NSW (allocated to Queensland by this site and federal Department of Health) are being used by both states to calculate remaining active cases. The jurisdiction in which these people were originally counted as confirmed cases is unclear. This site reports the number of active cases as announced by each state.​

    • The sum of Victoria’s reported recoveries, deaths and active cases does not equal the total number of cases reported by that state. As of 22 May 2020, this site reflects Victoria’s figures as reported despite this discrepancy. This is because federal figures appear to mirror Victorian figures as reported.

  • On 22 May 2020, Australia’s Chief Nursing and Midwifery Officer reported a total national figure of active cases. It was the first time the federal government reported this number. The figure of active cases was the sum of all active cases as reported by states and territories.

When does an active case become a recovery?

The answer varies across states and territories.

  • The national guidelines for COVID-19 define conditions for release from isolation:

    • For asymptomatic cases, at least 10 days must pass without symptoms since the first positive test sample was taken;

    • For mild cases, at least 10 days must pass since the onset of symptoms, and there must have been no acute symptoms in the last 72 hours; and

    • There are further conditions for people who were hospitalised or will enter high-risk settings such as health care or residential age care facilities.

  • Spokespersons for ACT Health, Queensland Health and WA Health each said recoveries are determined by public health officials who monitor patient symptoms and make a determination based on the national guidelines. The Queensland Health website also refers to cases with a notification date of 30 days or more. A spokesperson for NT Health said a patient must return two consecutive negative test results. NSW Health has published recoveries are assessed three weeks after the onset of illness by interviewing the case. Cases reporting no symptoms are considered to have recovered. Cases who have not recovered at three weeks are called in the following weeks until recovery. A response is pending from SA Health. Victoria Health and Tasmania Health have not responded to questions clarifying their processes.

Notes on transmission sources

Summary: To see the latest announcements and changes relating to transmission sources, use the charts on the homepage or national transmission sources page. To see the overall figures that most closely represent the underlying and adjusted state and territory data on transmission sources, view the charts on the state/territory transmission source page.

  • Capturing the messages and representations made to the public about transmission sources is not always straight-forward. There are several sources of information that may report transmission sources: press conferences held by state and territory leaders; datasets, web pages and dashboards managed by states and territories; and daily updates or snapshots from the Department of Prime Minister and Cabinet and federal Department of Health.

  • The key difference between these sources is the date on which transmission sources are reported. (Obtuse language in press conferences can also be a challenge). Daily updates are static representations of cases and report transmission sources as an event that occurred in the previous 24 hours. However, some states that provide transmission sources via datasets or dashboards report them on the date of case notification, which may be before the previous 24 hours. This applies to NSW, Victoria and ACT. Data NSW has confirmed cases are notified on the date of test sample taken.

  • This has several impacts:

    • For NSW, Victoria and ACT, the daily announcements of transmission sources – whether they be in press conferences or federal snapshots – will not necessarily match the dates of those transmission sources in their datasets.

    • The national view of transmission sources is a static display of cases that shows the developments in the past 24 hours. This includes allocation of new cases (which may or may not have been notified in that 24 hour period, depending on when the test sample was taken) and reallocation of older cases after further investigation. Therefore it will not necessarily show transmission sources on the same dates as NSW, Victoria or ACT.

  • In general, this site ​reports information against the date it is announced or published, not the date on which a case is notified (which we do not always know).

  • However, for transmission sources, this site now uses different approaches for different charts:

    • The Last Week of Transmission Sources chart on the homepage, sources its data primarily from updates and announcements made at daily press conferences and Department of Prime Minister and Cabinet (delivered later in the day and may prompt reconciliation of data). Note, this represents a change in approach as this chart previously sourced data for NSW, Victoria and ACT from their respective dashboards. The reason for the change is that, while case-line data is generally preferable, the goal of this chart is to show what has been announced to the public today, and that generally reflects what has developed or changed in the last 24 hours. I.e. How many new overseas, known and unknown contacts did a state or territory add yesterday?

    • The charts on the page Transmission sources: national charts are an extension of the above graph and are updated later in the day. They also primarily source data from Prime Minister & Cabinet and daily announcements. (The PM&C updates can occasionally be unreliably distributed, causing a possible delay in these charts).

    • The charts on the page Transmission sources: state and territory charts source their respective data from the best possible source for that jurisdiction. For NSW, Victoria and the ACT, that is their case-line data. Therefore the charts for those jurisdictions on this page, show cases against the dates of case notifications. This means the dates of transmission sources in these charts will be different from those in the national and summary charts.

    • There is one caveat to the final point above. As previously noted, cases are reported on this site against the date they were announced or published to the public, which means cases recorded on today’s date refer to yesterday’s reporting period (with the exception of Tasmania – see notes on confirmed cases and deaths above). This creates confusion when case-line data (which has no delay) is placed alongside announcement-date data (which has one day’s delay). Therefore, an artificial adjustment has been made in the Transmission sources: state and territory charts for NSW and Victoria, in which the case-line data as reported by those states has been shifted forward by one day, to synchronise dates with the rest of the charts on this site.

  • Those jurisdictions that do not provide case-line data have a different issue – it means that after a case is announced as ‘under investigation’ it is not often revisited for the sake of clarifying the transmission source to the public. This particularly occurs in Queensland. It affects the charts of daily transmission sources, but it’s recommended you view the charts of cumulative totals on the transmission sources: state and territory charts page.

  • Charts go back as far as respective available data allow. This varies depending on the jurisdiction.
  • Negative values have been included in most charts to show movement between categories, but large removals of ‘under investigation’ cases have not always been included.

  • Transmission source updates are limited on Saturdays due to availability of data.

This article is part of the COVID-19 in Australia infograms collection:

Cases: active and recovered

Cases: states and territories

Daily briefing

Data notes



Hospitalisations, ICUs, and ventilators

In focus: Victoria COVID-19 infograms

Overseas comparisons


Transmissions: national

Transmissions: states and territories

This data is curated from Juliette O’Brien’s website. Juliette is supported by Tanveer Bal, Ananth Selladoray, Robert de Graaf and Naveen Kaushik from OutputAI Labs. Collaborators: Anthony Little, Rahul Vashisth, Noel Mathews, Rashid Elhawli, Shruti Khunte, Shrey Sharma, Suraj Enumula.


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