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**Giuseppe** · February 13, 2009, 11:26 AM

Re: Case definitions for the 4 diseases requiring notification to WHO - WER

Case definitions for the 4 diseases requiring notification to WHO in all circumstances under the IHR (2005) (WHO WER, 2/13/2009)

Case definitions for the 4 diseases requiring notification to WHO in all circumstances under the IHR (2005)

[Original text at LINK. EDITED.]

[From the Weekly epidemiological record - 13 FEBRUARY 2009, 84th YEAR - No. 7, 2009, 84, 49?56 - Excerpts.]

Under the terms of the International Health Regulations (2005) (IHR (2005)), WHO is to establish case definitions for the following 4 critical diseases that are deemed always to be unusual or unexpected and may have serious public health impact, and hence must be notified to WHO in all circumstances: smallpox, poliomyelitis due to wildtype poliovirus, human influenza caused by a new subtype and severe acute respiratory syndrome (SARS).

* These case definitions are specifically for purposes of notification under the IHR (2005) and may not apply to other surveillance or reporting systems, which may have their own definitions.

* The IHR (2005) also require notification of all (public health) events that may constitute a public health emergency of international concern, in accordance with the Decision Instrument (contained in Annex 2).

Human influenza caused by a new subtype

Case definition for notification of human influenza caused by a new subtype under the IHR (2005) States Parties to the IHR (2005) are required to notify WHO immediately of any laboratory-confirmed case of a recent human infection caused by an influenza A virus with the potential to cause a pandemic. Evidence of illness is not required for this report.

An influenza A virus is considered to have the potential to cause a pandemic if the virus has demonstrated the capacity to infect a human and if the haemagglutinin gene (or protein) is not a variant or mutated form of those, i.e. A/H1 or A/H3, circulating widely in the human population.

An infection is considered recent if it has been confirmed by positive results from polymerase chain reaction (PCR), virus isolation, or paired acute and convalescent serological tests. An antibody titre in a single serum is often not enough to confirm a recent infection and should be assessed by reference to valid WHO case definitions for human infections with specific influenza A subtypes.

Poliomyelitis due to wild-type poliovirus

Case definition for notification of poliomyelitis due to wild-type poliovirus under the IHR (2005). Under the IHR (2005), a notifiable case of poliomyelitis due to wild-type poliovirus is defined as a suspected case, with isolation of wild poliovirus in stool specimens(1) collected from the suspected case or from a close contact of the suspected case.

A suspected case is defined as a child aged <15 years presenting with acute flaccid paralysis (AFP2), or as an individual of any age presenting with paralytic illness if poliomyelitis is suspected.

Note concerning notification of wild-type or vaccinederived poliovirus from sources other than AFP cases. In addition to notification of laboratory-confirmed cases of poliomyelitis due to wild-type poliovirus (a disease designated in Annex 2 of the IHR (2005) as ?unusual or unexpected and that may have serious public health impact?), the isolation of wild-type or vaccinederived
poliovirus from other human or non-human sources (from people without paralysis, or from environmental samples) must generally also be notified to WHO under the separate notification requirement for ?events that may constitute a public health emergency of international concern? as they fulfi ll at least 2 of the 4 criteria for notification.

Severe acute respiratory syndrome (SARS)

Case definition for notification of SARS under the IHR(2005). In the period following an outbreak of SARS, a notifiable case of SARS is defined as an individual with laboratory confirmation of infection with SARS coronavirus (SARS-CoV) who either fulfils the clinical case definition of SARS or has worked in a laboratory handling live SARS-CoV or storing clinical specimens infected with SARS-CoV.

Clinical case definition of SARS

1. A history of fever, or documented fever

AND

2. One or more symptoms of lower respiratory tract illness (cough, difficulty breathing, shortness of breath)

AND

3. Radiographic evidence of lung infiltrates consistent with pneumonia or acute respiratory distress syndrome (ARDS) or autopsy findings consistent with the pathology of pneumonia or ARDS without an identifiable cause

AND

4. No alternative diagnosis fully explaining the illness.

Diagnostic tests required for laboratory confirmation of SARS

a) Conventional reverse transcriptase PCR (RT-PCR) and real-time reverse transcriptase PCR (real-time RT-PCR) assay detecting viral RNA present in:

1. At least 2 different clinical specimens (e.g. nasopharyngeal and stool specimens)

OR

2. The same clinical specimen collected on 2 or more occasions during the course of the illness (e.g. sequential nasopharyngeal aspirates)

OR

3. a new extract from the original clinical sample tested positive by 2 different assays or repeat RT-PCR or realtime RT-PCR on each occasion of testing

OR

4. virus culture from any clinical specimen.

b) Enzyme-linked immunosorbent assay (ELISA) and immunofluorescent assay (IFA)

1. Negative antibody test on serum collected during the acute phase of illness, followed by positive antibody test on convalescent-phase serum, tested simultaneously

OR

2. A 4-fold or greater rise in antibody titre against SARSCoV between an acute-phase serum specimen and a convalescent-phase serum specimen (paired sera), tested simultaneously.

Editorial note.

In the absence of known SARS-CoV transmission to humans, the positive predictive value of a SARS-CoV diagnostic test is extremely low; therefore, the diagnosis should be independently verified in />1 WHO international SARS reference and verification network laboratories. A single case of SARS must be reported to WHO under the IHR (2005). A detailed exposure history is an essential part of the diagnostic work-up for any person under investigation for SARS. More information on SARS surveillance can be found at: http://www.who.int/csr/resources/pub.../en/index.html.

Infections with SARS-CoV that occur as a result of breaches in laboratory biosafety or biosecurity should be fully investigated.

Once an outbreak of SARS has been independently verified by one or more WHO international SARS reference and verification network laboratories, WHO will make the appropriate case definitions for surveillance and reporting available through its usual well-established mechanisms.

Smallpox

Case definition for notification of smallpox under the IHR (2005). States Parties to the IHR (2005) are required to notify to WHO immediately of any confirmed case of smallpox.

The case definition for a confirmed smallpox case includes the following:

Confirmed case of smallpox
An individual of any age presenting with acute onset of fever (≥38.3 ?C/101 ?F), malaise, and severe prostration with headache and backache occurring 2?4 days before onset of rash

AND

Subsequent development of a maculopapular rash starting on the face and forearms then spreading to the trunk and legs, and evolving within 48 hours to deep-seated, firm or hard and round well-circumscribed vesicles and later pustules, which may become umbilicated or confluent

AND

Lesions that appear at the same stage of development (i.e. all are vesicles or all are pustules) on any given part of the body (e.g. the face or arm)

AND

No alternative diagnosis explaining the illness

AND

Laboratory confirmation.

Editorial note.

In contrast to the varicella (chickenpox) infection with centripetal and more superficial lesions, the majority of smallpox cases present with a characteristic rash that evolves slowly over days (with each stage lasting 1?2 days) at the same rate and is centrifugal in distribution, i.e. predominantly concentrated on the face and extremities, with usual involvement of the palms and soles of the feet.

Further information and illustrative examples to differentiate smallpox from chickenpox can be found at http://www.who.int/csr/disease/small.../en/index.html.

The risk of not identifying atypical presentations of smallpox is weighed against the extremely low risk of reintroducing of the disease and the very high risk of obtaining a false-positive laboratory result. In view of this, laboratory tests to confi rm smallpox should be limited to individuals who match the above clinical case definition. Should a single, laboratory-confirmed case of
smallpox ever occur, it would be considered an outbreak since smallpox no longer exists as a naturally occurring disease.
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1) As a standard procedure, 2 stool specimens are collected from an AFP case within 14 days of paralysis onset. Since virus excretion in the stool decreases beyond 2 weeks after paralysis onset, and to increase the sensitivity of virus detection, additional stool specimens from up to 5 close contacts are taken from AFP cases for whom 2 specimens collected within 14 days of paralysis onset are not available.
2) Poliomyelitis cannot be diagnosed reliably on clinical grounds because other conditions presenting with acute paralysis can mimic poliomyelitis. Surveillance for polio eradication therefore requires the reporting of all children aged <15 years with acute onset fl accid paralysis, with subsequent laboratory testing of stool specimens.
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Announcement

Case definitions for the 4 diseases requiring notification to WHO - WER

Case definitions for the 4 diseases requiring notification to WHO - WER

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