Revised surveillance case definitions: Chlamydia; diphtheria; hepatitis E; pertussis

This report provides the revised Surveillance case definitions approved by the Communicable Diseases Network Australia (CDNA) since 1 January 2013.

Page last updated: 03 October 2013

This report provides the revised Surveillance case definitions approved by the Communicable Diseases Network Australia (CDNA) since 1 January 2013.

The Case Definitions Working Group (CDWG) is a subcommittee of the CDNA and comprises members representing all states and territories, the Australian Government Department of Health (DoH), the Public Health Laboratory Network (PHLN), OzFoodNet, the Kirby Institute, the National Centre for Immunisation Research and Surveillance (NCIRS) and other communicable disease experts. CDWG develops and revises surveillance case definitions for all diseases reported to the National Notifiable Diseases Surveillance System. Surveillance (NNDSS) case definitions incorporate laboratory, clinical and epidemiological elements as appropriate.

The following case definitions have been reviewed by CDWG and endorsed by CDNA.

These case definitions were implemented on 1 July 2013 and supersede any previous versions.

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Chlamydia

(Excluding eye infections)
(Effective 1 July 2013)

Reporting

Only confirmed cases should be notified.

Confirmed case

A confirmed case requires laboratory definitive evidence.

Laboratory definitive evidence

Isolation of Chlamydia trachomatis
OR
Detection of C. trachomatis by nucleic acid testing
OR
Detection of C. trachomatis antigen.
END

Chlamydia changes

Added to title (Excluding eye infections)

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Diphtheria

(Effective 1 July 2013)

Reporting

Both confirmed cases and probable cases should be notifed.

Confirmed case

A confirmed case requires laboratory definitive evidence AND clinical evidence.

Laboratory definitive evidence

Isolation of toxigenic Corynebacterium diphtheriae or toxigenic Corynebacterium ulcerans.

Probable case

A probable case requires:

Laboratory suggestive evidence AND clinical evidence
OR
Clinical evidence AND epidemiological evidence.

Laboratory suggestive evidence

Isolation of Corynebacterium diphtheriae or C. ulcerans (toxin production unknown).

Clinical evidence

At least one of the following:

Pharyngitis and/or laryngitis (with or without a membrane)
OR
Toxic (cardiac or neurological) symptoms.

Epidemiological evidence

An epidemiological link is established when there is:

Contact between two people involving a plausible mode of transmission at a time when:

a) one of them is likely to be infectious (usually up to 2 weeks and seldom more than 4 weeks after onset of symptoms)
AND
b) the other has an illness which starts within approximately 2-5 days after this contact
AND
At least one case in the chain of epidemiologically linked cases (which may involve many cases) is laboratory confirmed.
END

Diphtheria changes

Confirmed case

At the end of confirmed case, added "AND clinical evidence"

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Hepatitis E

(Effective 1 July 2013)

Reporting

Only confirmed cases should be notified.

Confirmed case

A confirmed case requires:

laboratory definitive evidence
OR
Laboratory suggestive evidence AND clinical evidence AND epidemiological evidence.

Laboratory definitive evidence

Detection of hepatitis E virus by nucleic acid testing
OR
Detection of hepatitis E virus in faeces by electron microscopy
OR
IgG seroconversion or a significant increase in antibody level or a fourfold or greater rise in titre to hepatitis E virus.

Laboratory suggestive evidence

Detection of IgM or IgG to hepatitis E virus.

Clinical evidence

A clinically compatible illness without other apparent cause.

Epidemiological evidence

Travel to a country with known hepatitis E activity between 15 – 64 days prior to onset
OR
epidemiological link to a confirmed case
END

Hepatitis E changes

Confirmed case

Added "OR Laboratory suggestive evidence AND clinical evidence AND epidemiological evidence"

Laboratory definitive evidence

Replaced "Detection of IgM or IgG to hepatitis E virus. If the person has not travelled outside Australia in the preceding 3 months, the antibody result must be confirmed by specific immunoblot" with "IgG seroconversion or a significant increase in antibody level or a fourfold or greater rise in titre to hepatitis E virus"

Added Laboratory suggestive evidence, Clinical evidence and Epidemiological evidence;

Laboratory suggestive evidence

Added "Detection of IgM or IgG to hepatitis E virus"

Clinical evidence

Added "A clinically compatible illness without other apparent cause"

Epidemiological evidence

Added "Travel to a country with known hepatitis E activity between 15 – 64 days prior to onset OR epidemiological link to a confirmed case"

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Pertussis

(Effective 1 July 2013)

Reporting

Both confirmed cases and probable cases should be notified.

Confirmed case

A confirmed case requires either:

Laboratory definitive evidence
OR
Laboratory suggestive evidence AND clinical evidence

Probable case

A probable case requires clinical evidence AND epidemiological evidence

Laboratory definitive evidence

Isolation of Bordetella pertussis
OR
Detection of B. pertussis by nucleic acid testing
OR
Seroconversion in paired sera for B. pertussis using whole cell or specific B. pertussis antigen(s) in the absence of recent pertussis vaccination1

Laboratory suggestive evidence

Significant change (increase or decrease) in antibody level (IgG, IgA) to B. pertussis whole cell or B. pertussis specific antigen(s)
OR
Single high IgG and/or IgA titre to Pertussis Toxin (PT)
OR
Single high IgA titre to Whole Cell B. pertussis antigen.

1In the absence of recent vaccination

Clinical evidence

A coughing illness lasting two or more weeks
OR
Paroxysms of coughing
OR
inspiratory whoop
OR
post-tussive vomiting.

Epidemiological evidence

An epidemiological link is established when there is:

Contact between two people involving a plausible mode of transmission at a time when:

a) one of them is likely to be infectious (from the catarrhal stage, approximately one week before, to three weeks after onset of cough)
AND
b) the other has an illness which starts within 6 to 20 days after this contact
AND
At least one case in the chain of epidemiologically linked cases (which may involve many cases) is a confirmed case with either laboratory definitive or laboratory suggestive evidence.

Pertussis changes

Confirmed case

Removed "Clinical evidence AND epidemiological evidence"

Probable case

Added "AND epidemiological evidence"

Laboratory definitive evidence

Added "OR Seroconversion in paired sera for B. pertussis using whole cell or specific B. pertussis antigen(s) in the absence of recent pertussis vaccination.

Added footnote "In the absence of recent vaccination".

Laboratory suggestive evidence

Changed to "In the absence of recent vaccination Significant change (increase or decrease) in antibody level (IgG, IgA) to B. pertussis whole cell or B. pertussis specific antigen(s) OR Single high IgG and or IgA titre" to Pertussis Toxin (PT) Single high IgA titre to Whole Cell B. pertussis antigen.

Added footnote "In the absence of recent vaccination".

To "A probable case requires clinical evidence only" added "AND epidemiological evidence"

Removed Clinical evidence for probable cases.

Moved Clinical evidence and Epidemiological evidence to Probable Case.

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