Technical Notes and Caveats on the Report of Overseas Acquired Vectorborne Diseases

This page provides further technical notes and details about the reports on cases of vectorborne disease acquired overseas and reported in Australia.

Page last updated: 03 March 2017

What data are included?

This report includes information about notifications in Australia of overseas acquired cases of the vectorborne diseases chikungunya, dengue, malaria and Zika, and other cases of rare or infrequently reported overseas-acquired vectorborne diseases. The data are extracted from the National Notifiable Diseases Surveillance System (NNDSS) and published fortnightly on Wednesdays, and contain data up to the previous Saturday.

New notifications are those with a notification received date within the past fortnight and may relate to cases of disease with onset in earlier time periods. The notification received date represents the date the notification of the disease was received by the communicable diseases section of the health authority.

Data tables are provided for chikungunya, dengue, malaria and Zika, using the by diagnosis date to define the period of interest. Diagnosis date represents the onset date, or where the onset date is unknown, the earliest of the specimen date, the notification date or the notification received date.

Both confirmed and probable cases of dengue and Zika are notifiable, and included in these reports, while only confirmed cases of chikungunya and malaria are notified.

Where can I find the case definitions?

The surveillance case definitions for notifiable arboviral diseases can be found on the Department of Health website.

What is the difference between a confirmed and probable case?

A probable dengue or Zika case is a case that meets laboratory suggestive evidence and epidemiological evidence (such as a compatible travel history) but does not currently meet the criteria for laboratory confirmation. Some of these probable cases will be later reclassified as confirmed when more laboratory evidence becomes available (such as a second blood sample), while some will remain probable because no further evidence is available.

Do these data include all cases of these vectorborne diseases in Australia?

A major limitation of the notification data is that, for most diseases, they represent only a proportion of the total cases occurring in the community, that is, only those cases for which health care was sought, a test conducted and a diagnosis made, followed by a notification to health authorities. The degree of under-representation of all cases is unknown and is most likely variable by disease and jurisdiction. This is particularly relevant for Zika, since the majority of infections are asymptomatic.

Only overseas acquired cases are included in this report. A single case of locally-acquired dengue in Queensland is considered an outbreak, and information about any current outbreaks of dengue can be obtained from the Queensland Health website.

Where can I get more information?

For further details on NNDSS and data interpretation, refer to Australia's notifiable diseases status: Annual report of the National Notifiable Diseases Surveillance System Annual report series published in Communicable Diseases Intelligence.

Acknowledgements

The Australian Government Department of Health acknowledges the Communicable Diseases Network Australia, the work of public health officers involved in the collection of surveillance data; state and territory public health communicable disease surveillance managers and data managers; and public and private laboratories.

The following link will return you to the reports:

Further information

For more information about these reports, contact epi@health.gov.au