Guidance for pathologists and anatomical pathology technologists for autopsy of cadavers with known or suspected pandemic (avian) influenza

There is concern about the procedures to be followed in the mortuary if and when there is a request to examine the body of a person who is known or suspected to have died from pandemic influenza. This includes avian influenza, on the premise that the A/H5N1 virus may evolve to produce the next human pandemic.

Although no one knows if there will be a pandemic, in the event of one the Dept of Health and Health Protection Agency (HPA) estimate the likely excess mortality in the UK to be at least 50,000 deaths (reference 1). The most critical cases will be those occurring early on during an epidemic; once health professionals become proficient at making a clinical diagnosis, the need for confirmatory in vivo laboratory and autopsy diagnosis will diminish.

The Dept of Health has produced guidance (reference 1), which includes much useful background information, as well as specific protection advice for those health care workers who may be exposed to aerosols containing the influenza virus - eg during an autopsy examination. In my opinion, this advice is appropriate for protection of pathologists, APTs and others potentially exposed in the mortuary environment, and should be followed.

1. Location of the autopsy
The HPA document on the management of unusual illnesses of infectious aetiologies (reference 2) refers to where autopsies are performed. If pandemic influenza infection is first suspected during the actual autopsy procedure, it is safer to continue with the examination, using appropriate protection, than to have the opened cadaver transported, potentially leaking, to another more specialised autopsy location.

2. Personal protection
This virus is categorised in Hazard Group 3. Standard universal precautions for autopsy work (scrub suit, complete cover gown, apron, gloves, eye protection) pertain. The critical issue concerns respiratory protection for those exposed to aerosols of virus.

The recommendation is for an EN149:2001 FFP3 disposable respirator. This is not a ventilated-visor head set, but a face mask that fits tight. It is widely available through NHS equipment providers. Several mortuaries already use them as routine face protection for all cases. It is appropriate as protection for viruses (as well as bacteria), but is not protection against chemical toxins.

Drug prophylaxis
Oseltamivir ('Tamiflu') has been proposed as a treatment for and prophylaxis against avian influenza. Pathologists and APTs should consult with the local occupational health unit whether this drug is appropriate for those exposed in a mortuary setting.

Vaccination
If and when a vaccine against avian influenza becomes available, front line health staff including those who work in mortuaries should be vaccinated via local occupational health units.

3. Specimen sampling
To establish the diagnosis of pandemic influenza if suspected at autopsy, or to confirm a previously suspected case, the correct samples need to be taken. The HPA has issued guidance for autopsy diagnosis for unusual illnesses from both chemical and biological agents, with emphasis on the agents likely to be used in bioterrorist attacks (reference 2). Although it did not specify avian pandemic influenza, the sample protocol is appropriate for this infection.

The samples for the microbiology departments include: lung tissue, urine, and blood. The blood should ideally include both whole blood (from a peripheral vein, ie external iliac or femoral) and serum from centrifugation of whole blood. If a centrifuge is not available in the mortuary, the blood sample should be presented to the microbiology department promptly for preparation there. Nasopharyngeal washings are also effective samples for diagnosis of respiratory tract viral infections; they should be transported in viral transport medium, or immediately to the department.

For histopathology, following formalin fixation, a standard set of samples should comprise all the major organs (including intestine (reference 3)), and must include lung, trachea and bronchus. Recommended sampling (reference 4):

* Central (hilar) lung with segmental bronchi

* Right and left primary bronchi

* Trachea (proximal & distal)

* Pulmonary parenchyma from right & left lung

A common mode of death in pandemic influenza is secondary bacterial pneumonia following the viral pneumonitis with ARDS, but other organs are also affected. Co-morbidities (eg ischaemic heart disease) will be relevant in determining whether patients survive or not, and need to be documented.

4. Communication concerning the autopsy and resultant diagnosis
The HPA document indicates the relevant people and authorities who will be concerned. They include the senior clinician in the case, the coroner, and the local Occupational Health Consultant. A list of potentially exposed staff in the mortuary should be kept (reference 2).

Professor Sebastian Lucas Dept of Histopathology Guy's & St Thomas' Hospital London SE1 March 2006 sebastian.lucas@kcl.ac.uk tel: 44-20-7188-2954

Reference documents

1. 'Guidance for pandemic influenza: infection control in hospitals and primary care settings'. Dept of Health & Health Protection Agency. Oct 2005.
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2. 'Initial investigation and management of outbreaks and incidents of unusual illnesses. With particular reference to events that may be due to chemical, biological or radiation causes, including deliberate releases'. Health Protection Agency. March 2004.
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3. Uiprasertkul M, et al. Influenza A H5N1 replication sites in humans. Emerg Infect Dis 2005; 11, issue 7.
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4. Guidelines for collecting and shipping specimens for influenza A (H5N1) diagnostics; from the California Dept of Health Services.
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