Guidance

Management of contacts of highly pathogenic avian influenza H5N1 during the 2023 to 2024 avian influenza season

Updated 1 February 2024

1. Introduction

Since October 2021, there has been an unprecedented outbreak of highly pathogenic avian influenza (HPAI) of the subtype H5N1 in wild birds within the UK and internationally. In addition to affecting wild bird populations, the virus has passed into farmed and captive flocks leading to a large number of infected premises (IP).

Within Europe, a small number of people have tested positive for H5N1 over the past year, all of whom were living with or working with H5N1-infected poultry. All cases were asymptomatic when tested.

Health protection teams (HPTs) lead the local human public health response to HPAI incidents involving large-scale commercial poultry establishments, smaller backyard premises or wild birds. Responding to these incidents requires close collaboration with the Department for Environment, Food and Rural Affairs (Defra), the Animal and Plant Health Agency (APHA), local authority and the local NHS.

The main updates included within this guidance relate to:

• public health follow-up of contacts who were wearing personal protective equipment (PPE) during exposure (see section 6.1)
• the definition of a probable case of HPAI H5N1 in wild birds (see section 3.1)

2. Purpose

This interim guidance is for HPTs planning for, and dealing with, the human health risk in people who have been exposed to confirmed or probable H5N1 HPAI in captive or wild birds during the 2023 to 2024 season (1 October 2023 to 30 September 2024).

A number of the sections of this guidance link to the existing guidance Managing the human health risk of avian influenza in poultry and wild birds in order to avoid repetition.

This interim guidance supersedes sections of the existing guidance for Managing the human health risk of avian influenza in poultry and wild birds, in relation to the public health follow-up of exposed people where testing identifies the causative strain of HPAI to be H5N1.

This interim guidance applies only where the presence of HPAI influenza A virus sub-type H5N1 is either confirmed or probable, during the 2023 to 2024 season. For all other subtypes of avian influenza, the existing UK Health Security Agency (UKHSA) guidance for Managing the human health risk of avian influenza in poultry and wild birds should continue to be followed.

Information on the management of symptomatic contacts and confirmed human cases of avian influenza is available separately.

3. Definitions

3.1 Bird case definitions

Confirmed case

A bird that has tested positive for influenza A H5N1 by APHA.

Probable case (applies to wild birds only)

A dead or ill bird which is within an APHA no-testing zone (usually within 3km and 14 days of a previous confirmed case) in a species which is listed as affected by HPAI H5N1 by APHA, will be treated as having probable H5N1 in the context of the current avian flu season. This will also apply where APHA advises that a bird should be treated as a probable case and testing will not be undertaken.

Unknown status case (applies to wild birds only)

Any other dead or ill wild bird not covered under the confirmed or probable case definition above.

3.2 Human contact definitions

The infectious period for bird cases is considered to start 72 hours before the onset of symptoms. APHA can provide an infectious period estimate for flocks if date of onset is unclear.

An individual meeting the exposure criteria below is defined as a contact whether or not PPE has been worn.

Farmed and captive flocks or birds

For farmed flock or captive birds, a contact includes any person who has:

• entered the APHA-declared IP where infected birds are kept (while birds are still within the premises or before cleaning, if the birds are no longer present)
• handled a bird from the IP or its faeces
• handled eggs or other poultry products from the IP

This applies for the duration of the infectious period for the flock or captive birds on the IP, and until APHA states that the IP are no longer infected.

Wild birds

For wild birds, a contact includes any person who has:

• been within one metre of a probable or confirmed bird case when the bird was alive in an enclosed space (for example in a building or vehicle)
• handled a probable or confirmed bird case (alive or dead) or its faeces

This applies for the duration of the infectious period for the affected birds.

Further detail to support HPT risk assessments of human contacts can be found in part one of Investigation and management of possible human cases of avian influenza amongst contacts associated with incidents.

3.3 Personal protective equipment (PPE)

Appropriate PPE is as described in the Health and Safety Executive (HSE) guidance Avoiding the risk of infection when working with poultry that is suspected of having H5 or H7 notifiable avian influenza.

PPE should be worn at all times when working in a potentially infected environment. Typically, this will comprise:

• disposable or polycotton coveralls with head coverage of CE type 5 and 6 that offer protection against dusts, splashes and liquid sprays (with safe disposal or cleaning after use)
• disposable gloves of lightweight nitrile or vinyl or heavy-duty rubber (not latex) gloves that can be disinfected
• rubber or polyurethane boots that can be cleaned and disinfected
• FFP3 respirator with exhalation valve (note that exhalation valve only applies to IP and is not a requirement for wild bird incidents – see section 21 of the Mitigation strategy for avian influenza in wild birds in England and Wales)
• close fitting goggles or other equipment that gives at least the same level of protection

All PPE should be suitable for the wearer and, where appropriate, must be fit-tested to the person.

3.4 Follow-up definitions

Active follow-up

This means the exposed person will have daily contact (by text, telephone or email) from UKHSA to check that the exposed person has not developed any symptoms compatible with human avian influenza. Any individual who develops symptoms will be immediately referred for clinical assessment as per the guidance on Investigation and management of possible human cases of avian influenza amongst contacts associated with avian influenza incidents.

Passive follow-up

This means the exposed person will be provided with information on human avian influenza symptoms, and will be given emergency contact instructions for the HPT. The individual will be told to contact the HPT if they develop any of the symptoms of avian influenza in the 10 days following the last date of exposure. Any individual who develops symptoms will be immediately referred for clinical assessment as per the guidance on Investigation and management of possible human cases of avian influenza amongst contacts associated with avian influenza incidents.

4. Employer responsibilities

Employers or contracting organisations are responsible for ensuring that staff have access to PPE, are trained in PPE donning, doffing and disposal and appropriate biosecurity and infection prevention and control. They should have appropriate assurance in place for their policies and procedures.

Employers and contracting organisations are responsible for ensuring that employees have access to an occupational health service who can provide management, including pathways to allow access to clinical care for diagnostic testing and prescription of treatment-dose antivirals, if symptomatic with avian influenza symptoms.

5. Principles of prevention of human infection with HPAI H5N1

In situations where H5N1 is suspected or confirmed, the following principles should apply:

• keep the number of people exposed to the infected birds to a reasonable minimum; this may need to be balanced against the need to undertake necessary control measures
• only those individuals required to enter IP for occupational reasons (such as for collection or disposal of birds and cleaning or decontamination) should have access to the premises
• people who are likely to be exposed as responders (and therefore become contacts) should be advised and trained on the appropriate use of PPE
• all contacts should be provided with information about HPAI including what to do if they develop symptoms of infection
• where antiviral post-exposure prophylaxis is indicated (see below), this should be started as soon as possible after exposure
• members of the public should be advised not to touch sick or dead wild birds – where removal and disposal of dead wild birds is required, individuals should follow the guidance in Section 21 of the Mitigation strategy for avian influenza in wild birds in England and Wales

6. Management of contacts of HPAI H5N1

Follow-up of contacts is determined by whether appropriate PPE was used.

The day of last exposure should be counted as day 0 for the purposes of determining duration of follow-up and the window for starting antivirals.

6.1 Follow-up of contacts where appropriate PPE was used

Contacts of probable wild bird cases or confirmed H5N1 in any birds or IP, where all the following apply, should receive passive follow-up:

• trained in the correct use (including donning and doffing) of PPE
• fit-tested for an FFP3 respirator
• wore the appropriate PPE with no breaches

Contacts should inform the local HPT if they develop symptoms. HPTs should refer to the guidance for Investigation and management of possible human cases of avian influenza amongst contacts associated with avian influenza incidents for further investigation and management. Symptomatic contacts may also need to inform their employer or occupational health provider.

6.2 Follow-up of contacts where appropriate PPE was not used

Contacts of a probable wild bird case or confirmed H5N1 in any birds who were not wearing appropriate PPE or had a breach in PPE at the time of exposure should:

• receive antiviral prophylaxis if within 7 days of exposure
• receive active follow-up if within 10 days of exposure

These contacts are likely to include individuals who were exposed prior to the identification of an incident, such as:

• farm workers
• owners of backyard flocks or other people resident at the premises who have had exposure to birds or infected materials
• veterinary staff
• members of the public who have had direct contact with a probable or confirmed wild bird case

6.3 Post-exposure antiviral prophylaxis

The standard recommended dosage for antiviral prophylaxis (also referred to as neuraminidase inhibitors) is 75mg of oseltamivir, once daily. This should be given as a 10-day course, and can be started up to 7 days following the last date when exposure occurred without complete PPE (unprotected exposure). The course should be started as soon as possible. Dose adjustment may be required for those with co-morbidities such as renal impairment.

For additional information on the use of antivirals please refer to Guidance on use of antiviral agents for the treatment and prophylaxis of seasonal influenza.

6.4 Duration of follow-up

Active follow-up should be undertaken every day up to 10 days from the last unprotected exposure, or for the duration of post exposure antivirals, whichever is longer.

For passive follow-up, contacts should be advised to contact the HPT if they develop any of the symptoms of avian influenza in the 10 days following their last exposure.

6.5 Follow-up of contacts of wild birds of unknown status

Members of the public who have handled birds with unidentified disease (or their faeces) do not require public health follow-up, unless information or risk assessment from APHA suggests a different approach.

7. Additional information and resources

Information on agency roles and responsibilities, the route of notifications of H5N1 incidents, and IMT resources can be found in the guidance for Managing the human health risk of avian influenza in poultry and wild birds.

This guidance also contains a template health questionnaire and antiviral factsheet for contacts.

National or locally developed information sheets should be utilised to provide information to contacts about H5N1, including symptoms.