This guidance covers:

• bird and other animal case definitions
• types of human exposure to infected birds or other animals, and the management of those individuals
• personal protective equipment (PPE), testing, antiviral use, and principles for health protection teams (HPTs)

1. Background and purpose

This guidance supports public health teams responding to human exposures to influenza A(H5) in birds or other animals. These recommendations are based on information available as of December 2024 and will be updated as further information becomes available. If using this guidance, check regularly for updates to this page, including changes to recommendations in this guidance.

Influenza A(H5) is currently circulating in birds and has caused mammalian outbreaks and human zoonotic infections globally. Due to reassortment with other avian viruses, there are a large number of genotypes, some of which have distinct properties. There is also the potential for mutations to be acquired which facilitate changes in the virus profile or host range.    

Following a new process approved by the Advisory Committee on Dangerous Pathogens (ACDP), a joint UK Health Security Agency (UKHSA), Animal and Plant Health Agency (APHA), and Department for Environment, Food and Rural Affairs (DEFRA) risk assessment will be undertaken at the start of each avian influenza season using available genomic, laboratory, and epidemiological data on influenza A(H5) viruses circulating in Europe and early seasonal wild bird detections in the UK. The risk assessment will guide the approach to the public health response to human exposures to birds or other animals infected with influenza A(H5) and associated premises for the season.

If, in the risk assessment, there are no signals of increased risk associated with the viruses circulating (such as frequent genomic features associated with mammalian adaptation, or a high rate of zoonotic cases previously associated with the same virus), this guidance document will cover the management of humans exposed to influenza A(H5) in birds or other animals and infected premises.

If, in the risk assessment, there are any features of a higher risk virus being detected or the situation changes suggestive of an increased risk, this guidance document would not apply. Instead, the ‘strict approach’ in which antivirals are offered to all those in contact with affected birds or other animals and infected premises, regardless of use of PPE, should then be used as an additional safeguard.

If the situation changes during the avian influenza season, the risk assessment will be revisited.

2.  Principles of prevention of human infection with influenza A(H5)

In situations where influenza A(H5) is suspected or confirmed in infected premises, or where there are potential exposure risks from birds or animals, the following principles should apply:

• keep the number of people exposed to the infected birds or animals and premises to a reasonable minimum; this may need to be balanced against the need to undertake necessary control measures
• reduce human risk by limiting the number of individuals required to enter infected premises for occupational reasons (such as for collection or disposal of birds or animals, and cleaning or decontamination) and those that should have access to the premises
• ensure that people who are likely to be exposed as responders (and therefore have the potential to become exposed individuals) are advised and trained on the appropriate and safe use of PPE, including donning and doffing, and should be fit-tested where appropriate

For working with suspected or confirmed infected poultry, the appropriate PPE is set out by the Health and Safety Executive (HSE) and consists of:

• disposable or polycotton coverall with head coverage of CE type 5 and 6 that offer protection against dusts, splashes, and liquid sprays (with, as appropriate, 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
• close fitting goggles or other equipment that gives at least the same level of protection

Subject to a local risk assessment undertaken by the employer, elements of this guidance may be relevant to work with other farm animals or in other agricultural settings.

All individuals deemed to have been exposed to influenza A(H5) should be provided with information about influenza A(H5), including what to do if they develop symptoms of infection. Where antiviral post-exposure prophylaxis is indicated, this should be started as soon as possible after exposure.

Advice for members of the public is not to touch sick or dead wild birds – where removal and disposal of dead wild birds is unavoidable, individuals should follow the advice in Avian influenza (bird flu) – advice for the public on staying safe by minimising contact with wild birds.

3. Animal case definitions: influenza A(H5)

The APHA has published detailed guidance on suspect case definitions, diagnostic criteria and testing in mammals, which should be used by HPTs in conjunction with the case definitions below in Table 1. The influenza A(H5) case definitions for birds and other animals below are for influenza A(H5N1) but can be used for other H5 subtypes. They may be updated or expanded if the evidence changes, so it is important to regularly refer to this page when using this guidance. The APHA Surveillance for Avian Influenza in Wild Birds and Wild Mammals in GB map can be used to inform HPTs where positive wild birds and animals are found, or where mass mortality events are reported in wild birds, as not all may have been tested.

Table 1. Infected bird and other animal definitions: influenza A(H5) (for use during avian influenza season, or in a restriction zone in or out of season)

Infected animal and premises definitions	Animal clinical definitions	Laboratory test results
Probable infection: wild (non-domestic) bird species, mammal or genus which is listed as affected by influenza A(H5) by APHA	Dead or clinical signs suggestive of infection with influenza A(H5) during avian flu season and informed by the extant wild bird risk level, or APHA advises should be treated as a probable case regardless of whether testing will be undertaken	Test results unavailable
Confirmed infection: individual bird or other animal, either domestic or non-domestic	Clinical signs suggestive of infection with influenza A(H5) based on clinical case definitions	Positive for presence of influenza A(H5Nx) virus (notifiable avian disease)
Infected premises: may include poultry, other non-domestic or domestic birds, or other animals	Clinical signs suggestive of infection with influenza A(H5) based on clinical case definitions	APHA have declared an infected premises following a positive influenza A(H5) result (PCR) from clinical samples of an animal in a herd/flock Chief Veterinary Officer has confirmed presence of disease

Note: Information on avian influenza in mammals is available from Influenza A(H5N1) infection in mammals: suspect case definition and diagnostic testing criteria.

4. Human exposure to influenza A(H5) from zoonotic source

HPTs should assess people potentially exposed to a zoonotic influenza A(H5) using Table 2 and classify them as having either high or low risk exposure (or not exposed). APHA can provide an infectious period estimate for the birds or other animals. When an influenza A(H5) infection has been confirmed in poultry, a minimum of a 3km protection zone is put in place around the infected premises by APHA or DEFRA. These are refreshed on the notifiable animal disease cases and zones site.

Examples provided are principles and should be considered as part of HPT risk assessments. For support, or where consensus cannot be reached locally, please contact acute.respiratory@ukhsa.gov.uk, or the Epidemic and Emerging Infections (EEI) consultant on-call (out of hours details circulated with the UKHSA Out of Hours rota).

Table 2. Human exposure to infected animals: influenza A(H5)

The table below classifies the types of potential human exposure (low- or high-) to probable or confirmed bird or other animal (captive or wild) cases, and suspected and confirmed infected premises, with influenza A(H5) as defined in Table 1.

Exposure risk	Description	Examples
Low: protected physical or respiratory exposure	Individual wearing full PPE as set out by HSE (with no breaches in PPE use) who has close contact with an infected animal/infected premises declared by APHA	Close or direct [note 1] contact with a bird or other animal [note 2] Close or direct exposure to the contaminated environment [note 3] of a bird or other animal Close or direct exposure to contaminated materials from birds or other animals, for example faecal material, animal produce such as eggs, milking equipment, or during poultry rendering
Low: no physical contact, unlikely respiratory exposure	An individual not wearing full PPE as set out by HSE, who undertakes any of the examples	A visit to or work on an infected premises with no contact with infected animals or their contaminated environment, for example walking through an infected premises staying more than 1 metre away from infected animals or contaminated environment [note 3] Encountering settings where there have been mass animal die offs in the previous 6 weeks [note 4] due to influenza A(H5), remaining more than 1 metre away from the animals or birds and/or their contaminated environment and/or their contaminated material [note 3]
High: unprotected physical or direct contact or likely respiratory exposure	An individual not wearing full PPE as set out by HSE, or who has had a breach in PPE use, who undertakes one or more of the examples	Close or direct [note 1] contact with a bird or other animal (captive or wild) [note 2] Close or direct exposure to the contaminated environment [note 3] of a bird or other animal Close or direct exposure to contaminated materials from birds or other animals, for example faecal material, animal produce including eggs, milking equipment or during poultry rendering A visit or work in an area where influenza A(H5) is suspected or confirmed (protection zone as defined by APHA) with close or direct contact with animal or bird [note 1] Encountering settings where there have been mass animal die offs in the previous 6 weeks due to influenza A(H5), and has close contact less than 1 metre with the animals or birds and/or or their contaminated environment and/or their contaminated material [note 3]

Notes

Note 1: close contact is defined here as within 1 metre (aligned with current ECDC advice). Includes veterinary workers, farm workers or people living on the farm, abattoir workers or equivalent (person giving direct care to an animal). 

Note 2: for example, wild birds, poultry, non-domestic, domestic, or mammals.  

Note 3: contaminated environment includes surfaces contaminated with animal or bird parts for example carcasses, internal organs, or faeces from influenza A(H5N1) infected animals or birds

Note 4: this period is based on limited data from experimental studies. There is insufficient evidence regarding other factors potentially affecting virus survivability.

5.  PPE for working with suspected or infected birds or other animals

The correct use of PPE should reduce exposure risk. However, due to the difficulty in effectively assessing PPE usage and compliance, use of PPE does not completely remove the possibility of exposure or infection.

Recommended PPE when working with poultry is described in the HSE guidance, Avoiding the risk of infection when working with poultry that is suspected of having H5 or H7 notifiable avian influenza. Subject to a local risk assessment undertaken by the employer, elements of this guidance may be relevant to work with other farm animals or in other agricultural settings.

PPE should be worn at all times when working in a potentially infected environment. All PPE should be suitable for the wearer and, where appropriate, must be fit-tested to the person.

6. Management of individuals exposed to influenza A(H5) in birds or other animals

People exposed to infected birds, other animals, or premises should be assessed according to their exposure risk by the HPT. Depending on level of exposure, individuals will receive active or passive follow-up and may require antiviral prophylaxis. Asymptomatic individuals who have been exposed may be eligible for recruitment to enhanced zoonotic influenza surveillance described in section 7. Any individual who develops symptoms within 10 days of exposure to influenza A(H5), should be referred for clinical assessment and testing as per section 8.

6.1 Low-risk exposure to birds or other animals with influenza A(H5)

Individuals who have low-risk bird or other animal exposures to influenza A(H5) do not require post-exposure antiviral prophylaxis. They should have passive follow up for 10 days. This involves providing the exposed person with information on influenza A(H5) and emergency contact instructions for the local HPT. The individual should be told to contact the HPT if they develop any of the clinical symptoms (described in section 9) in the 10 days following the last date of exposure. Any individual who develops symptoms will then be immediately referred for clinical assessment.

6.2 High-risk exposure to birds or other animals with influenza A(H5)

Antiviral prophylaxis should be offered to individuals with high-risk exposures to influenza A(H5) as soon as possible (ideally within 48 hours) with an oseltamivir treatment dose course (75mg twice daily for 5 days). This recommendation is based on limited data that support higher chemoprophylaxis dosing for avian influenza A(H5N1) virus infection, and aims to reduce the potential for the development of antiviral resistance while receiving once daily chemoprophylaxis. Treatment can be started up to 7 days after the last exposure but is likely to be less effective if delayed; rapid access to antivirals should be a priority. For additional guidance on dosage recommendations, such as for those with renal impairment or treatment by age group, see Patient Group Direction (PGD) for the supply of oseltamivir for pre and post exposure of avian influenza .

People who have high-risk animal and bird exposures to influenza A(H5) should also have active follow up for 10 days following the last exposure. This involves daily contact (by text, telephone, or email) to check that the exposed person has not developed any symptoms compatible with human avian influenza. Any individual who develops symptoms should be notified to the local health protection  team and referred for clinical assessment.

Table 3 summarises the actions for individuals exposed to influenza A(H5). Categories of high- and low-level exposure are defined in Table 2.

Table 3. Exposure matrix for individuals exposed to influenza A(H5) in birds or other animals

Exposure risk (linked to animal exposure defined in Table 2)	Public health advice	Testing protocol	Post-exposure chemoprophylaxis
Low	Advise low risk exposure and provide relevant advice Contact can carry out normal activities (no restrictions) Passive monitoring for 10 days from last exposure	Diagnostic nose and throat swab if any respiratory symptoms develop and diagnostic conjunctival swab if conjunctivitis symptoms develop If asymptomatic, advise that they may be contacted about taking part in enhanced zoonotic influenza surveillance	None
High	Advise high risk exposure and provide relevant advice Active follow-up for 10 days from last exposure Advise them to isolate if they develop symptoms, and follow the advice provided to them	Diagnostic nose and throat swab if any respiratory symptoms develop and diagnostic conjunctival swab if conjunctivitis symptoms develop If asymptomatic, advise that they may be contacted for enhanced zoonotic influenza surveillance.	Recommend oseltamivir 75mg twice daily for 5 days (with dose adjustment where relevant) Prophylaxis should be started as soon as possible, ideally within 48 hours, but can be started up to 7 days after last exposure

7. Zoonotic influenza enhanced surveillance

In the event of an infected premises with confirmed influenza A(H5) in birds or animals, a zoonotic influenza enhanced surveillance protocol may be instigated to detect the infection in potentially exposed individuals who consent to take part, as part of UKHSA enhanced surveillance. This involves sampling at baseline (entry to protocol) and days 2, 5 and 8 after exposure for individuals where the exposure is acute. This may include capillary blood samples, and in some situations venous blood and oral fluid samples. Serological samples at baseline and 21 days after enrolment would also be taken where possible.

This enhanced surveillance is run by UKHSA, and sampling undertaken by the UKHSA Rapid Investigation Team.

8. Management of symptomatic individuals who have been exposed to influenza A(H5)

Any individual who develops signs or symptoms (see section 9) of an influenza-like illness (ILI) or conjunctivitis, or any severe infectious illness that does not have a plausible alternative explanation, within 10 days of high- or low-risk exposure to influenza A(H5), should be risk assessed for possible influenza A(H5) infection. Where initial assessment (for example by the HPT) has been unable to exclude influenza A(H5), testing should be arranged. Clinical assessment should take place in an acute NHS setting or via locally agreed or commissioned services.

If the individual or HPT is concerned about their symptoms or they are getting worse, then they should contact NHS 111 and tell them they have been potentially exposed to avian influenza. If the exposed individual becomes seriously unwell and requires urgent medical attention, then they should telephone 999 and tell them they have been potentially exposed to avian influenza.

Influenza A(H5) has been classified as an airborne high consequence infectious disease (HCID) requiring transmission-based-precautions and enhanced PPE (including donning and doffing procedures) as outlined in the National Infection Prevention and Control Manual (NIPCM) addendum for HCIDs for acute care settings.

9. Diagnostic testing, and results

This section provides a clinical case definition to support clinicians on when to suspect influenza A(H5) in a patient (section 9.1), and epidemiological case definitions to support HPTs with the public health management of incidents where people may have been exposed to influenza A(H5) in birds or other animals (section 9.2).

The initial assessment of a potential HCID case must be conducted in strict accordance with the trust’s established HCID Assessment Pathway Protocol. This protocol aligns the required steps, documentation, and escalation procedures to ensure accurate risk assessment, timely intervention and compliance with national and local guidelines.

If carrying out an in-person clinical assessment, then before continuing:

1. Isolate the patient in a single occupancy room, preferably a respiratory isolation room and ideally under negative pressure; positive pressure rooms must not be used. Minimise patient contact with or exposure to staff and other patients, and ask the patient to wear a surgical mask when outside the room.

2. Ensure transmission-based-precautions and enhanced PPE (including donning and doffing procedures), as outlined in the National Infection Prevention and Control Manual (NIPCM) addendum for HCIDs.

3. Start oseltamivir treatment dose course (75mg twice daily for 5 days) if the patient meets clinical case definition for avian influenza (see section 9.1 below).

9.1 When to clinically suspect influenza A(H5) in exposed symptomatic individuals

This section provides guidance for clinicians on when to suspect influenza A(H5) in patients who are symptomatic and who have been exposed.

Influenza A(H5) may be suspected when:

a patient presents with any one or more of the relevant signs or symptoms [note 5], influenza-like illness (ILI) or conjunctivitis, or any severe infectious illness that doesn’t have a plausible alternative explanation

and in the 10 days prior to symptom onset, they had either:

i: close contact (within 1 metre) with:

• live, dying, or dead domestic poultry or wild birds, including live bird markets in an area of the world (including within the UK) affected by avian influenza [note 6]
• any animal suspected or confirmed of having avian influenza

Or:

ii: close contact [note 6] with:

• a confirmed human case of avian influenza
• human cases of unexplained illness resulting in death from affected areas [note 7]
• human cases of severe unexplained respiratory illness from affected areas [note 7]

Notes

Note 5: signs and symptoms may include one or more of:

• acute uncomplicated upper respiratory tract signs and symptoms also referred to as ILI (fever at or above 37.8°C plus cough or sore throat)
• fever or feeling feverish
• cough
• sore throat
• runny or stuffy nose
• muscle or body aches
• headaches
• fatigue
• eye redness (or conjunctivitis)
• shortness of breath or difficulty breathing

Less common signs and symptoms include:

• diarrhoea
• nausea
• vomiting
• seizures
• other severe or life-threatening illness suggestive of an infectious disease process such as multi-organ failure or meningoencephalitis

It is important to remember that infection with influenza viruses, including avian influenza A viruses, does not always cause fever.

Note 6: this includes from 1 day prior to symptom onset and for duration of symptoms or positive virological detection: handling laboratory specimens from cases without appropriate precautions, being within 1 metre distance of the case, directly providing care, touching a case, being within close vicinity of an aerosol generating procedure for a case. 

Note 7: see the UKHSA list of HCID country-specific risks. If unsure, discuss with UKHSA TARZET Acute Respiratory Team acute.respiratory@ukhsa.gov.uk in hours or the Emerging and Epidemic Infectious consultant out of hours.

If the patient is considered to meet this clinical case definition, the local clinician or microbiologist should:

• contact the duty microbiologist or virologist at the nearest regional UKHSA Clinical Network Laboratory (CNL - previously known as the Public Health Laboratory) to discuss sampling and testing arrangements
• if the CNL duty microbiologist or virologist agrees that testing is indicated, follow the laboratory investigations algorithm and inform the local HPT

9.2 Epidemiological case definitions for public health management (for HPTs)

Epidemiological case definitions in Table 4 are provided to support HPTs with public health response to potential cases resulting from zoonotic spillover and should not be used by clinicians to determine which individuals should be assessed for clinical diagnostic testing.

Table 4. Human case definitions for cases resulting from zoonotic spillover for influenza A(H5)

Human case definition	Exposure to infected bird or other animal [note 8]	Human clinical [note 9] case definition	Laboratory test results
Possible	Any exposure to an infected bird, other animal, or premises in the 10 days prior to symptom onset	Any signs or symptoms [note 10], influenza-like illness (ILI) or conjunctivitis, or any severe infectious illness that doesn’t have a plausible alternative explanation	Not yet tested for influenza A or pending a test result [note 11]
Probable	Any exposure to an infected bird, other animal, or infected premises in the 10 days prior to symptom onset	Any signs or symptoms [note 10] or ILI or conjunctivitis, or any severe infectious illness, that doesn’t have a plausible alternative explanation, or an asymptomatic detection such as screening/study.	Influenza A positive or unsubtypable or subtype unavailable in local PCR assays
Confirmed	Any known or unknown exposure to animals or birds	Any presentation including asymptomatic detected on screening	Influenza A(H5) subtyped by a UKHSA laboratory (either respiratory or conjunctival sample)

Notes

Note 8: epidemiological criteria include persons with recent (within 10 days) high- or low-level exposure to a confirmed or probable infected animal or suspected or infected premise.

Note 9: influenza-like illness (ILI) is defined as fever at or above 37.8°C and cough or sore throat. Where the index of suspicion is raised due to exposure or comorbidity, clinician and public health specialists should assess atypical presentations on a case-by-case basis.

Note 10: signs and symptoms may include one or more of:

• acute uncomplicated upper respiratory tract signs and symptoms also referred to as influenza-like illness (ILI) (fever at or above 37.8°C plus cough or sore throat)
• fever or feeling feverish
• cough
• sore throat
• runny or stuffy nose
• muscle or body aches
• headaches
• fatigue
• eye redness (or conjunctivitis)
• shortness of breath or difficulty breathing

Less common signs and symptoms include:

• diarrhoea
• nausea
• vomiting
• seizures
• other severe or life-threatening illness suggestive of an infectious disease process, such as multi-organ failure or meningoencephalitis

It is important to remember that infection with influenza viruses, including avian influenza A viruses, does not always cause fever.

Note 11: asymptomatic individuals who have been exposed to zoonotic influenza are not routinely tested. They may be tested following risk assessment, on a case-by-case basis, taking into account the level and timing of exposure and the epidemiological context, for example as part of a study of the first few X cases (FFX).

Case definitions

Historic case: an individual with serological confirmation of influenza A(H5) infection by an appropriate test and sample, who has not tested positive for influenza A(H5) in a molecular laboratory test (PCR and/or sequencing).

Discarded case: an individual who was initially classified as a possible or probable, who tested negative for influenza A(H5) at the UKHSA CNL or Respiratory Virus Unit (RVU) with appropriately timed samples (while likely to be shedding virus – within 5 days of symptom onset or if asymptomatic, within 10 days of last exposure).

Unresolved case: an individual who was initially classified as a possible or probable case who had symptoms but either did not get tested (PCR and or sequencing) or was tested (PCR and or sequencing) but the results were uninterpretable (for example, testing was not conducted within the 10 days after exposure).

9.3 Laboratory investigations and sample handling

Laboratory investigations, sample transfer instructions including roles for the UKHSA duty doctor microbiologist or virologist, Respiratory Virus Unit (RVU), EEI Consultant and the HPT are outlined in the laboratory investigations algorithm and are summarised below.

Note: it is helpful to have 2 swabs of each type (for example 2 upper respiratory tract swabs) submitted for testing to the relevant CNL to allow sufficient material for any additional confirmatory work to be performed.

Diagnostic testing should be undertaken for symptomatic individuals who have been exposed to infected birds, other animals, or premises. Testing should be as follows: 

• 2 upper respiratory tract swabs (for example, a combined nose and throat viral swab, or nasopharyngeal swab or aspirate) collected into viral transport medium (VTM) – this must be obtained from all individuals regardless of whether respiratory symptoms are present or not
• 2 viral eye (conjunctival) swabs collected into VTM if there are symptoms of eye infection or conjunctivitis; collect 2 swabs from each eye if both eyes are affected
• if obtainable/clinically appropriate, a lower respiratory tract sample (sputum, or an endotracheal tube aspirate if intubated)
• all samples for suspected avian influenza testing must be collected into VTM (not lysis buffer) and handled at containment level 3 and transported in Category B packaging as per the lab investigations algorithm.

For patients in hospital, the local clinician or microbiologist should contact the UKHSA CNL duty microbiologist or virologist for testing. If the CNL duty microbiologist/virologist agrees that testing is indicated, follow the laboratory investigations algorithm, and the local clinician/microbiologist should inform the local HPT of the suspicion of avian influenza.

HPTs are asked to inform the UKHSA Acute Respiratory Infections team (via acute.respiratory@ukhsa.gov.uk), the UKHSA CNL duty microbiologist or virologist (by phone and email), and phone the EEI consultant on-call (if out of hours). The UKHSA CNL will inform the RVU by email or telephone (in-hours).  

The UKHSA CNL microbiologist or virologist will respond to this email chain to report all results (positive and negative) to the HPT, referring laboratory, RVU, UKHSA Acute Respiratory Infections Team, and the EEI duty consultant, or will phone if appropriate.  

Positive results for influenza A(H5) or influenza A unsubtypeable results resulting from animal exposures described above, must be phoned to the acute respiratory infections consultant (in hours) or EEI consultant on-call (out of hours), who will inform the National Response Centre (NRC), on-call (0300 303 3493). Positive or equivocal samples must be discussed with RVU before forwarding the sample for confirmatory testing.

Diagnostic testing for other potential causes of acute respiratory illness should also be considered depending upon the local epidemiology of circulating respiratory viruses, such as SARS-CoV-2. A negative influenza A screening test alone may not fully exclude avian influenza in a suspected case. Diagnostic assurance work is performed for influenza A detection and A(H5) subtyping assays in use in the UKHSA laboratories to ensure appropriate detection capability for known circulating strains.

For international reporting purposes, all confirmed cases (those with positive results for influenza A(H5) subtype) should have samples sent to RVU for confirmation. RVU will perform whole genome sequencing on samples from A(H5) positive cases. Confirmed cases will need reporting to the World Health Organization within 24 hours of confirmation via the national focal point (IHRNFP@ukhsa.gov.uk).

If testing has been undertaken through community systems deployed as part of response, these will have equivalent arrangements to UKHSA CNLs.

10. Results and repeat sampling

Actions to take in line with test results are as follows.

Positive influenza A(H5) subtype at UKHSA CNL: 

• isolate and manage as a confirmed case
• UKHSA CNL will discuss with RVU and arrange urgent forwarding of samples to RVU for confirmation
• reserve baseline serum sample; UKHSA will advise on further testing

Influenza A detected but unsubtypeable (or subtyping not available) at local laboratory (such as an NHS laboratory) and has relevant exposure for H5 avian influenza:

• isolate and manage as probable case pending further test results
• ensure 2 samples (collected into VTM) are sent to UKHSA regional CNL for A(H5) subtyping
• if the UKHSA regional CNL is unable to determine subtype (unsubtypeable sample) or avian influenza testing results are inconclusive, UKHSA CNL to contact RVU to discuss results and options for further testing and to arrange forwarding of samples to RVU
• UKHSA CNL to immediately report result to referring laboratory and RVU

Test result is negative in a UKHSA Clinical Network Laboratory (CNL) for influenza A AND H5 subtyping or influenza A detected and subtyped as seasonal A(H3) or A(H1) AND A(H5) negative:

• de-isolate
• provide the patient with standard influenza advice as appropriate including where to seek treatment if indicated
• if new clinical symptoms develop as defined in the case definition within 10 days of last exposure, re-test
• if appropriate samples were obtained and an alternative diagnosis is likely, then A(H5) may be considered excluded. If clinical suspicion remains, including possible non-A(H5) zoonotic influenza, the UKHSA CNL duty microbiologist/virologist should contact the RVU reference laboratory to discuss results and options for further testing

10.1 Indeterminate results

Where the UKHSA laboratory results are indeterminate (for example, due to poor sample quality, timing of sampling, low viral load sample, degradation during transport), further sampling may be advised. This may include upper respiratory tract samples, conjunctival swabs, or lower respiratory tract samples, depending on the clinical status. Advice on the management of individuals with indeterminate results, or where clinical suspicion remains despite negative testing, will need to be sought from a public health virologist and the acute respiratory infections consultant (in hours) or EEI consultant on-call (out of hours), on a case-by-case basis.