Case definition / clinical features
Health Protection Agency revised interim guidelines for investigation and reporting of suspected human cases of avian influenza
Comments to: Respiratory Disease Department, Centre for Infections, Health Protection Agency ( 
respcdsc@hpa.org.uk 44 (0)20 8327 7768)
Link to PDF format (PDF, 98 KB)
- The following guidelines are based on WHO guidelines for case investigation in countries without any A/H5 (avian) influenza activity in animals. WHO is recommending enhanced surveillance for A/H5 influenza infection in humans.
- February and March is peak influenza season in parts of East Asia cases of normal human influenza in people entering the UK from Asia can be expected.
- Cases meeting all the components of the definition below (clinical, travel and contact) should be
a. Investigated for influenza A/H5 as below,
b. Reported using the report form on this website,
c. Discussed with the local Health Protection Team at an early stage.
- The WHO published case definitions on 29 August 2006. The following is the HPA's case definition.
Please note that if epidemiological criteria are definitely fulfilled and patient is severely unwell but with no respiratory symptoms the case should be discussed with the HPA Centre for Infections.
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1. |
Clinical presentation |
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Fever ( ? or = 38°C) OR history of fever AND respiratory symptoms (cough or shortness of breath) requiring hospitalisation. |
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AND |
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2 |
Epidemiological criteria |
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History of travel in the 7 days prior to onset of symptoms to an area affected by avian influenza A (H5N1) ( click here to see updated list in the Algorithm A3) AND close contact (within 1 metre) with live or dead domestic fowl, wild birds, or swine in any setting, including bird markets. A list of affected countries is available here. < http://www.hpa.org.uk/infections/topics_az/avianinfluenza/situation_update.htm>.
OR one of the following: |
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a. |
Close contact ( touching/speaking distance) with other case(s) of severe respiratory illness or unexplained death from above areas. |
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b. |
Part of a Health Care Worker cluster of severe unexplained respiratory illness. |
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c. |
A Laboratory worker with potential exposure to influenza A (H5N1) |
- Local and regional laboratories with appropriate biosafety and diagnostic facilities should confirm influenza A infection in above cases using IFA or other method.
- WHO recommends that specimens from such cases are handled using biosafety level 2 standards and biosafety level 3 work practices. See: < http://www.who.int/csr/disease/avian_influenza/guidelines/handlingspecimens/en/>
- If influenza A infection is diagnosed, or if local diagnosis is not possible (click here for a list of regional influenza A (H5) testing laboratories) , consultation must be sought with Dr Maria Zambon,Virus Reference Division (VRD), HPA Colindale: < http://www.hpa.org.uk/srmd/div_vrd_ernvl/index.htm>, tel.: 020 8327 6269
The following specimens will be required for confirmation of A (H5) infection:
- Viral specimen - NPA or throat swab
- Specimen for PCR - NPA or throat swab
Isolation and infection control
- Although human to human transmission of A (H5) has not yet been described the consequences of transmission are potentially severe.
- WHO is recommending the use of high-efficiency masks, contact and droplet precautions. See: < http://www.who.int/csr/disease/avian_influenza/guidelines/infectioncontrol/en>
- Pending the development of UK specific infection control guidelines, it is recommended that all cases of suspected A/H5 influenza (see case definition) be managed as for cases of suspected SARS. See:
< http://www.hpa.org.uk/infections/topics_az/SARS/hosp_infect_cont.htm>
- In addition, health care workers caring for cases of suspected A/H5 should be considered for prophylaxis with oseltamivir.
Specialist advice should be sought. Antiviral treatment with either oseltamivir or zanamivir should be actively considered.
Initial report of a suspected case should be to a Consultant in Communicable Diseases Control (CCDC) at your local Health Protection Unit.
- A case report form is available on the HPA website.
- CCDCs should inform their Regional Epidemiologist and the Respiratory Diseases Department at the Centre for Infections by telephone (020 8327 7768)
The possibility of SARS should also be considered in patients admitted with a severe unexplained respiratory illness with a history of recent travel to an area classified by WHO as having recent local transmission: < http://www.who.int/csr/sars/en/index.html>
Current case definitions for SARS may be found at: < http://www.hpa.org.uk/infections/topics_az/SARS/casedef.htm>
Last reviewed: 19 August 2008