Deaths due to acute respiratory infections in Australia methodology

This publication contains provisional counts of deaths involving COVID-19, influenza, and respiratory syncytial virus (RSV) by date of occurrence for Australia.

In response to the COVID-19 pandemic in Australia, the Provisional Mortality Statistics series was introduced in June 2020, and articles regarding COVID-19 Mortality in Australia were initially attached to this publication. 

As the pandemic has progressed, there has been a re-emergence of other acute respiratory diseases. To reflect this, the ABS broadened the scope of the articles to include deaths involving COVID-19, influenza and respiratory syncytial virus (RSV) from April 2024. Previous articles can be accessed from past issues of the Provisional Mortality Statistics publication, but the reported numbers of deaths in older articles are continually superceded by updated figures. For current figures, we recommend using the most recently published information. 

Provisional Mortality Statistics will now be published quarterly, while the information previously provided in the attached articles will be published more frequently. This necessitated separating the information previously provided in the attached articles into their own publication.

All data presented in this publication is provisional and the death records include coroner and doctor certified deaths that have been registered and received by the ABS. It is expected that numbers of deaths due to these causes will increase for more recent time periods as more death registrations are received by the ABS. Until it has been finalised, the data is subject to continuous quality improvement.

Death counts in this report will not be comparable with those reported in Deaths, Australia or Causes of Death, Australia. Differences are explained in more detail throughout the methodology. Death counts in this report may also not be comparable with other data sources based on the provisional data. 

The scope includes:

• deaths occurring and registered in Australia, including those persons with an overseas usual residence
• deaths occurring within Australian Territorial waters
• deaths occurring in Australian Antarctic Territories or other external territories (including Norfolk Island)
• deaths occurring in transit (i.e. on ships or planes) if registered in the Australian state or territory of 'next port of call'
• deaths of Australian Nationals overseas and employed at Australian legations and consular offices (i.e. deaths of Australian diplomats while overseas) where able to be identified. 

The scope excludes:

• deaths of Australian residents occurring outside Australia when registered by individual Registrars
• repatriation of human remains where the death occurred overseas
• deaths of foreign diplomatic staff in Australia (where these can be identified)
• stillbirths (fetal deaths). 

The registration of deaths is the responsibility of the eight individual state and territory Registrars of Births, Deaths and Marriages.

When a death occurs, the cause of that death is either certified by a doctor using a Medical Certificate of Cause of Death (MCCD), or the death is referred to a coroner for further investigation. For doctor certified deaths, information about the cause of death is supplied by the medical practitioner certifying the death via the MCCD (or MCCPD for perinatal deaths). Other information about the deceased is supplied via the Death Registration Form (DRF), which is informed by a relative or other person acquainted with the deceased, or by an official of the institution where the death occurred. Registrars require information from both sources to complete a death registration. It should be noted that legislative requirements for registering a death differ across jurisdictions and this can impact on the timeliness of registration and reporting.

Information is provided to the Australian Bureau of Statistics (ABS) by individual Registrars for processing, coding and compilation into aggregate statistics. Registrars report all deaths that were registered in a month at the start of the following month.

The following diagram shows the process undertaken in producing causes of death statistics in Australia. 

This publication draws extensively on information collected from the state and territory Registries of Births, Deaths and Marriages. Their continued cooperation is very much appreciated. Without it, the wide range of vitals statistics published by the ABS would not be available. 

Data in this report includes selected acute respiratory associated deaths registered by the end of a given month, by date of occurrence. When looking to measure change over time, the completeness of data for the most recent reported period is important.

When data is received each month by the ABS, the lag between the date of death and the date of registration means that approximately 40-50% of reported registrations are of deaths that occurred in the month being reported. The remainder are deaths that occurred in earlier months.  

For deaths which are doctor certified, approximately 95% of registrations are received after a second month of reporting. This is considered sufficiently complete to enable meaningful comparison with historical counts, noting that the level of completeness will be higher for the start of any given month than the end of that month. This publication reports on all of the death registrations the ABS has received, despite the most recent months being incomplete.

For coroner certified deaths, the proportion of registrations reported after a second month is lower, as it takes longer for coroners to certify deaths due to the complexity of investigations. Coroner certified deaths are included in the all-cause data and this may lower the completeness rate for more recently published weeks (see Data Release section of the methodology for more information on what data is available based on certification type).

Conditions on the medical certificate of cause of death are coded to the International Classifications of Diseases, 10th revision (ICD-10) (see Standards and classifications section of the methodology for more information). ICD-10 codes are assigned to all conditions on a MCCD and rules applied to select an underlying cause of death. The World Health Organization (WHO) defines the underlying cause of death as the disease or injury that initiated the train of morbid events leading directly to death. Accidental and violent deaths are classified according to the external cause, that is, to the circumstances of the accident or violence which produced the fatal injury rather than to the nature of the injury. Data presented in this publication is tabulated according to the underlying cause of death.

Diseases and conditions reported on the MCCD that are not the underlying cause of death are referred to as associated causes. Associated causes can be either: 

• Conditions listed in the causal sequence (the chain of events leading to death); or
• Pre-existing chronic conditions, often listed in Part II of the MCCD as ‘other conditions relevant to the death’.

Examining conditions in the causal sequence can provide insights into how a disease progresses and leads to death. Examining pre-existing chronic conditions provides an understanding of risk factors that might contribute to death from a particular disease. Both can inform health prevention and intervention policies.

Age-standardised death rates (SDRs) enable the comparison of death rates over time and between populations of different age-structures. The ABS uses the direct method of age-standardisation which allows for valid comparisons of mortality rates between different study populations and across time. This method was agreed to by the ABS, Australian Institute of Health and Welfare (AIHW) and other stakeholders. For further information see: AIHW (2011) Principles on the use of direct age-standardisation in administrative data collections: for measuring the gap between Indigenous and non-Indigenous Australians. Cat. no. CSI 12. Canberra: AIHW.

SDRs for specific causes of death with fewer than a total of 20 deaths have not been published due to issues of robustness. For further information, see Appendix: Principles on the use of direct age-standardisation, from Deaths, Australia, 2010.

SDRs in this publication have been calculated using quarterly estimated resident population (ERP) published in National, state and territory population. See 'Revision status' in the Methodology section for details of the status of quarterly population data used for calculating baseline rates. The quarterly estimates used for calculating weekly rates for the relevant year are as follows:

• weeks 1-13 - Mar quarter ERP
• weeks 14-26 - Jun quarter ERP
• weeks 27-39 - Sep quarter ERP
• weeks 40-53 - Dec quarter ERP.

The ABS publishes two regular reports that provide preliminary information on mortality - Provisional Mortality Statistics and Deaths due to acute respiratory infections in Australia. These reports provide information on different time periods and serve different purposes.

Provisional Mortality Statistics focuses on monitoring patterns of mortality (by all-causes and specified leading causes of death). Data must be sufficiently complete to detect such changes, and as such these reports are only released once the majority of deaths that occurred in a particular period have been registered and reported.

Deaths due to acute respiratory infections in Australia focuses on all deaths registered and reported with selected acute respiratory infections (COVID-19, influenza or RSV) written on the death certificate up until a specified time. These articles include important information about these acute respiratory infection certified deaths, including demographic details. While it is recognised data will be incomplete, it can still indicate emerging trends or changes among these deaths

This report contains statistics compiled using different methods to those used when compiling annual data on deaths and causes of death.

Key differences include:

1. This report is based on the date the death occurred. Annual reports are based on the date of registration.
2. This report is based on the state or territory of registration. Annual reports are based on the state or territory of usual residence of the deceased.
3. Data in this report is provisional. Data released in annual reports is final (except for revisions for coroner referred deaths). 

Causes of death are either certified by a doctor or a coroner. In Australia approximately 86-89% of deaths are certified by a doctor.

Almost all external causes of death (e.g. suicides, accidents and assaults) are referred to a coroner.

Although there is variation across jurisdictions, deaths are generally reportable to a coroner in circumstances such as:

• where the person died unexpectedly and the cause of death is unknown
• where the person died in a violent or unnatural manner
• where the person died during, or as a result of, an anaesthetic
• where the person was 'held in care' or in custody immediately before they died
• where the identity of the person who died is unknown. 

For the causes reported in this publication, approximately 5-6% of deaths involving COVID-19 and RSV have been certified by a coroner and just under 10% of deaths involving influenza have been certified by a coroner.

Each death registration in the national mortality dataset has 3 dates:

• when the death occurred
• when the death was registered with the jurisdictional Registry of Births, Deaths and Marriages (RBDM)
• when the death was lodged with the ABS.

Data in this report is based on date of occurrence.

Date of occurrence and date of registration will differ for all deaths, and the length of time by which they differ can vary considerably. Deaths are not reported to the ABS until they are registered, so the length of time between death and registration affects:

• the timeliness of information reported
• the ability to measure true change in mortality over time. 

The average time lag between death and registration can vary, although in general, deaths certified by a doctor are registered sooner. Coroner certified deaths undergo extensive investigative processes which can delay registration times and conclusions regarding the cause of death. Data regarding causes of death in this publication includes both doctor and coroner certified deaths.

Data in this release is compiled by state or territory in which the death was registered. In most cases, the death is registered in the state in which it occurred. Data in Deaths, Australia and Causes of Death, Australia is compiled by the state or territory of usual residence of the deceased, regardless of where in Australia the death occurred and was registered.

Deaths occurring in other territories of Australia are included in the jurisdictional dataset in which they are registered. For example, any deaths occurring on Christmas Island are registered by the Western Australian Registry of Births, Deaths and Marriages and presented in Western Australian outputs. The only exception to this is Norfolk Island where deaths are registered by the Norfolk Island Regional Council. Deaths occurring in Norfolk Island are included in Australia totals only. A very small number of deaths occur on Norfolk Island each year. 

Deaths of persons usually resident overseas which occur in Australia are included in the state/territory in which their death was registered. 

Statistics in this release are provisional and will be subject to additional processes prior to being released as part of the annual Deaths and Causes of Death datasets. Changes may occur in:

• the number of deaths
• demographic variables
• certifier type
• causes of death. 

Counts of deaths in the annual Deaths, Australia and Causes of Death, Australia are considered final. Causes of death for coroner referred deaths are subject to a revisions process. Further information on this revisions process can be found in the Methodology for Causes of Death, Australia.

As registrations for deaths that occurred in previous reference periods are sent to the ABS, these will be counted against their date of occurrence. Therefore, each release will represent a more complete count of the number of deaths that occurred in that reference period.

Data can be impacted by changes within one or more of the Registries of Births, Deaths and Marriages and therefore caution should be exercised when assessing week to week movements.

The Census and Statistics Act 1905 provides the authority for the ABS to collect statistical information, and requires that statistical output shall not be published or disseminated in a manner that is likely to enable the identification of a particular person or organisation. This requirement may restrict access to data at a very detailed level.

The International Classification of Diseases (ICD) is the international standard classification for epidemiological purposes and is designed to promote international comparability in the collection, processing, classification, and presentation of causes of death statistics. The classification is used to classify diseases and causes of disease or injury as recorded on many types of medical records as well as death records.

The ICD is revised periodically to incorporate changes in the medical field. Currently the ICD 10th revision is used for Australian causes of death statistics.

The ICD-10 is a variable-axis classification meaning that the classification does not group diseases only based on anatomical sites, but also on the type of disease. Epidemiological data and statistical data are grouped according to:

• epidemic diseases
• constitutional or general diseases
• local diseases arranged by site
• developmental diseases
• injuries. 

For example, a systemic disease such as sepsis is grouped with infectious diseases; a disease primarily affecting one body system, such as a myocardial infarction, is grouped with circulatory diseases; and a congenital condition, such as spina bifida, is grouped with congenital conditions.

For further information about the ICD refer to WHO International Classification of Diseases (ICD).

The Update and Revision Committee (URC), a WHO advisory group on updates to ICD-10, maintains the cumulative and annual lists of approved updates to the ICD-10 classification. The updates to ICD-10 are of numerous types including the addition and deletion of codes, changes to coding instructions and modification and clarification of terms.

From the 2013 reference year, the ABS implemented a new automated coding system called Iris.

Data coded in the Iris system applies updated versions of the ICD-10 when coding multiple causes of death, and when selecting the underlying cause of death. Information on Iris and ICD-10 versioning can be found in the table below. For details of further impacts of this change from 2013 data onwards, see the ABS Implementation of the Iris Software: Understanding Coding and Process Improvements Technical note, in the Causes of Death, Australia, 2013 publication and Updates to Iris coding software: Implementing WHO updates and improvements in coding processes Technical note, in the Causes of Death, Australia, 2018 publication.

The cumulative List of Official ICD-10 updates can be found online.

Australian cause of death data is coded to ICD-10 which is governed by the WHO. Case definitions, certification guidelines and coding rules have been implemented for international use.

Deaths due to influenza have been coded to J09-J11, and deaths due to RSV have been coded to J12.1, J20.5, J21.0, B34.8 with B97.4.

In response to the emergence of COVID-19 the WHO issued new emergency codes to be used when coding causes of death for statistical purposes.

Due to the public health importance of COVID-19, the WHO directed that the new coronavirus strain be recorded as the underlying cause of death, i.e. the disease or condition that initiated the train of morbid events, when it is recorded as having caused death.

• Deaths due to COVID-19: A death directly due to COVID-19 is defined by the WHO as a death resulting from a clinically compatible illness, in a probable or confirmed COVID-19 case, unless there is a clear alternative cause of death that cannot be related to COVID disease (e.g. trauma). There should be no period of complete recovery from COVID-19 between illness and death.
• COVID-19 related-deaths (dying with COVID-19): A COVID-19 related death is one where there is a disease or injury pathway to death that is not directly caused by the virus. For example, a person may have late stage cancer that has metastasised extensively causing organ damage leading to death. This person may also have contracted COVID-19. While the virus or it's complications may have negatively impacted health in an immuno-compromised person, the virus itself did not cause the terminal event leading to death (e.g. organ failure caused by metastases).

The international rules and guidance for selecting the underlying cause of death for statistical tabulation apply when COVID-19 is reported on a death certificate. COVID-19 is not considered as due to, or as an obvious consequence of, other diseases and conditions. These rules are also applied to cause of death coding for Influenza and selected other infectious diseases. There is no provision in the classification to link COVID-19 to other causes or modify its coding in any way.