Guidance

Investigation and management of outbreaks of suspected acute viral respiratory infection in schools: guidance for health protection teams

Updated 1 July 2024

Glossary and note on terminology

‘Pupil’ should be read as pupil, student, or child depending on the context. ‘School’ is also used to mean college and nursery.

1. Executive summary

This document provides guidance for local health protection teams (HPTs) about assessing and managing outbreaks of suspected acute viral respiratory infection (ARI) in schools and colleges including schools for pupils with special educational needs and disabilities (SEND). Approaches to response, including recommendations on testing, may be applicable in related settings such as early years or nurseries and school holiday clubs.

Seasonal influenza viruses and other respiratory viruses like rhinovirus and respiratory syncytial virus (RSV) cause outbreaks of ARI in schools, most commonly from autumn to spring. Since early 2020, SARS-CoV-2, the novel coronavirus that causes coronavirus disease (COVID-19), has been in circulation within the UK and has led to cases and outbreaks linked to schools. All these viruses can present with similar symptoms and so it is essential that suspected ARI outbreaks in schools are investigated and managed appropriately.

Central to the approach to these settings is the communication of key preparedness messages to schools, including awareness of arrangements for reporting outbreaks to local HPTs, public health exclusion advice for unwell children (which will vary depending on the respiratory diagnosis), as well as national childhood immunisation programmes such as that for influenza.

Schools are experienced in management of cases of childhood respiratory viruses. Schools may contact HPTs if they have concerns related to:

• a higher than previously experienced and/or rapidly increasing number of pupil or staff absences due to ARI
• evidence of severe disease due to ARI, for example if a pupil or staff member is admitted to hospital, particularly critical care (intensive care or a high dependency unit)
• a cluster of cases where there are concerns about the health needs of vulnerable staff or pupils within the affected group, including special schools
• control of transmission in boarding or residential school environments

Epidemiological definitions of cases and outbreaks are primarily used for surveillance purposes and should not be taken as indicating thresholds for HPT referral or public health action.

A key intervention to limit the transmission of flu in schools is to ensure successful delivery of the childhood flu immunisation programme in eligible year groups. In flu outbreak situations, antivirals may also be considered for unvaccinated exposed children in clinical risk groups, in line with national guidance, such as that published by the National Institute for Health and Care Excellence (NICE) (TA158) and the UK Health Security Agency (UKHSA).

UKHSA has produced guidance on health protection in schools and other childcare facilities, which includes advice on specific situations (for example public health exclusion advice) which should be read in parallel with this guidance.

Separate considerations will apply for residential educational settings and special schools (see appendices 1 and 2).

2. Background

Seasonal influenza, COVID-19 and other ARIs may transmit rapidly between children of school age, prompting the occurrence of localised outbreaks within schools. It is important to note that localised influenza outbreaks in school settings may precede circulation of seasonal influenza in the wider population. Co-circulation of multiple viruses is possible in a school or community. Other common viruses causing ARI in children include RSV, rhinovirus, human metapneumovirus (hMPV), adenovirus and parainfluenza.

Symptoms of ARIs (see section 4. ‘Definitions’) in children are difficult to distinguish between causative agents. Public health virological testing is not routinely undertaken for school outbreaks but may be considered by the consultant in health protection or other senior health protection staff if circumstances suggest that it may be useful for more complex ARI outbreaks. This could include outbreaks where there is a combination of:

• high numbers of children in clinical risk groups exposed or unwell
• there is a high attack rate
• multiple cohorts affected
• there are reports of hospitalisations or deaths

Rapid multiplex testing in these circumstances may provide useful information for the management of these outbreaks and intelligence but will also provide important intelligence for surveillance purposes.

Influenza vaccines are offered to many children by the NHS. The childhood flu vaccination programme is now an integral part of the national seasonal influenza vaccination programme. Schools may have a direct role in facilitating delivery of influenza vaccination for their pupils, including promotion. The national flu immunisation programme letter includes detailed information on plans for the forthcoming season.

As in previous influenza seasons, seasonal influenza vaccination is also available for individuals aged 6 months and older in clinical risk groups, as specified in the Green Book and the national influenza immunisation programme letter. National recommendations on childhood COVID-19 vaccination are summarised in the Green Book.

HPTs should be aware that when they receive a report of ARI in school-age children during the influenza season, some of those in the affected school may have already received seasonal influenza vaccination.

3. Preparedness measures

Achieving high uptake of the seasonal childhood influenza vaccination programme in schools is a key component of influenza preparedness. The aim is to reduce the public health impact of influenza by:

• providing direct protection to children, helping to prevent a large number of cases of influenza in children
• providing indirect protection by interrupting influenza transmission from children, averting cases of severe influenza and influenza-related deaths in older adults and people in clinical risk groups

Many schools have existing arrangements to identify ARI among pupils, such as monitoring of related absences. Schools should be aware of how to seek advice when they observe increases in ARIs, including risk assessment of potential outbreak situations.

Schools may also be aware of individual pupils who are in clinical risk groups (as part of the school’s health and welfare arrangements) and this information will be important for the rapid provision of information to families of these children during an outbreak.

It is useful for schools to be signposted to guidance on health protection in schools and other childcare facilities, including public health exclusion advice, prior to the beginning of the influenza season.

4. Definitions

The term acute respiratory infection (ARI) includes presentations both of influenza-like illness (ILI) and other acute viral respiratory infection syndromes.

See appendices 1 and 2 for additional considerations in residential educational settings and special schools.

Epidemiological definitions of cases and outbreaks are primarily used for surveillance purposes and should not be taken as indicating thresholds for HPT referral or public health action. School staff concerns will continue to be an important trigger for HPT referral and public health action. This is more likely in settings with high proportions of children who are in clinical risk groups for influenza vaccination, such as those with severe and profound learning disabilities.

4.1 Symptoms of ARI

Symptoms of influenza, COVID-19 and other common respiratory infections can include:

• continuous cough

• high temperature, fever or chills

• loss of smell, loss of taste or change in taste, often metallic

• shortness of breath
• malaise (unexplained tiredness, lack of energy)
• myalgia (muscle aches or pains that are not due to exercise)
• anorexia (not wanting to eat or not feeling hungry)
• headache that is unusual or longer lasting than usual
• sore throat,
• coryza (stuffy or runny nose)
• diarrhoea
• nausea or vomiting

4.2 Case definition for influenza-like illness (ILI)

Influenza-like illness (ILI) is defined in an education or early years setting as:

• acute onset of fever AND cough (in the absence of other diagnoses)
• if measured, fever is defined as equal to or over 37.8°C

It is acknowledged that influenza may vary in presentation in children, such as without fever or with diarrhoea, among others. These would not meet the ILI definition above, therefore if there is a suspicion of influenza in such children with these other clinical presentations, they would only be regarded as a case with a positive laboratory testing result for influenza.

Other symptoms associated with influenza include malaise (tiredness), headache, myalgia (muscle pain), diarrhoea, nausea or vomiting, sore throat and shortness of breath.

4.3 Case definition for confirmed influenza

A confirmed case of influenza is an individual with laboratory or point of care test (POCT) detection of influenza virus from a respiratory sample (usually a nose or throat swab). HPTs should be aware of the limitations of test performance particularly when not administered by a professional.

4.4 Definition for ARI outbreak

A suspected ARI outbreak in a non-residential school or educational setting is defined as:

• the occurrence of 2 or more cases of ARI symptoms (including ILI symptoms) within a 5-day period
• with an epidemiological link to the school or educational setting
• without laboratory confirmation

Epidemiological evidence of transmission within the school includes both cases having attended the school on at least one of the 5 days before onset in the absence of a known, alternative source of infection (for example a household member reported to have ILI). This is an indicative, pragmatic window and specific incubation periods and periods of communicability can be taken into consideration related to specific ARI pathogens (see section 5. ‘Epidemiological parameters’).

The epidemiological likelihood of a respiratory outbreak being due to influenza is increased if influenza has been declared to be circulating in the general community and particularly if there is evidence of local influenza transmission.

Epidemiological definitions of cases and outbreaks are primarily used for surveillance purposes and should not be taken as indicating thresholds for HPT referral or public health action.

4.5 Definition for confirmed influenza outbreak

Two or more laboratory confirmed cases of influenza among individuals (pupils or staff) with an epidemiological link to the educational setting arising in an ARI outbreak. Other ARI pathogen detections should be taken into consideration in defining cause, noting cocirculation is possible.

4.6 Definition for other confirmed ARI outbreaks

Two or more laboratory or POCT-confirmed cases of the same ARI pathogen (including any typing or sequencing if done) among individuals (pupils or staff) with an epidemiological link. to the educational setting arising in an ARI outbreak. Other ARI pathogen detections should be taken into consideration in defining cause, noting cocirculation is possible.

5. Epidemiological parameters

5.1 Influenza

Incubation period

The median incubation period of influenza is 2 days (range 1 to 4 days).

Infectious period

For influenza the period of infectiousness (that is communicability) starts with the onset of ILI symptoms and lasts for the duration of acute symptoms such as coryza and fever (cough or fatigue can be prolonged and alone do not indicate infectiousness).

5.2 COVID-19

Incubation period

Before Omicron the median incubation period of COVID-19 was 5 days (range 1 to 14 days). Studies of the Omicron variant suggest the median and mean incubation period is between 2 and 6 days, with a large UK study estimating a mean incubation period of between 3 and 4 days).

Infectious period

The vast majority of transmission events happen up to 5 days after symptom onset, but may occur later.

5.3 Other common respiratory viruses

These include:

• respiratory syncytial virus (RSV)
• rhinovirus
• adenovirus
• parainfluenza
• human metapneumovirus

All may have similar symptoms to other ARI.

Incubation periods vary between respiratory viruses, but are usually between 12 hours and 5 days, extending up to 8 days for RSV and parainfluenza. For further information see the epidemiological information summary, in the care home ARI HPT guidance, the review by Lessler and others (2009) the standard textbooks and manuals held by HPTs.

6. Investigation of outbreaks

6.1 Risk assessment

When an ARI outbreak is initially notified to an HPT, the information listed in 6.1.1 below will be useful to inform a risk assessment. This will help the HPT assess the likelihood of influenza as well as the severity and extent of the outbreak and will help to guide control measures. Equivalent local checklists may be deployed. This information should be captured on the HPZone outbreak or situation record. Schools are experienced in management of cases of childhood respiratory viruses and are most likely to contact HPTs when they have specific concerns such as high absence rates, severe cases, or setting-specific concerns such as as residential or special needs. Schools may also seek advice on lower risk and smaller outbreaks and HPTs should advise accordingly.

6.1.1 Information to be collected in the event of an ARI outbreak

The following information about the school or educational setting should be collected:

• details of the contact person at the school, including their job title and direct contact number
• size of the school (number of staff and number of pupils) and the size of cohorts affected (for example classes or year groups) if the illness is limited to specific cohorts
• type of school: day pupils only, boarders or both (see Appendix 1)
• whether the school is for pupils with SEND or whether there are pupils with SEND within the mainstream school (see Appendix 2)
• dates of childhood influenza vaccination and coverage rates in the school pupils and staff, if relevant and readily available

The following information about characteristics of the outbreak should be collected:

• nature of the symptoms
• number of cases among pupils and staff, both clinically suspected and laboratory confirmed (including specific laboratory results such as influenza subtype, if known)
• distribution of cases over time, including onset date of the first and most recent cases and according to class or year group
• number of hospitalisations, critical care admissions and deaths associated with the outbreak
• information on whether there are any pupils or staff in clinical risk groups in the school, if known

The following information about control measures should be collected:

• current infection prevention and control (IPC) measures
• actions taken in response to suspected outbreak
• communications with the school community to date

6.2 Virological investigation

Routine virological investigation of school ARI outbreaks is not essential for every outbreak but should be considered in:

• outbreaks involving significant numbers of children in clinical risk groups, such as in some special schools
• complex outbreaks, such as those involving high attack rates, multiple cohorts, prolonged outbreak duration, reported hospitalisations, critical care admissions or deaths among pupils or teachers

Any sampling that is undertaken to identify the causative organism for an ARI outbreak in a school should be informed by national and local surveillance data.

Virological confirmation of influenza in particular is most useful in the inter-seasonal period and early in the influenza season, when national surveillance schemes have not yet confirmed that influenza is circulating widely in the community. During these periods, other respiratory viruses may be as likely as seasonal influenza to cause ILI presentations. Laboratory testing can therefore inform the risk assessment and subsequent public health advice for individuals in risk groups who may benefit from antivirals.

Testing for respiratory viruses

When complex ARI school outbreaks arise, the HPT should consider testing symptomatic individuals for a broad range of respiratory viruses including influenza A, influenza B and RSV.

When swabbing is indicated HPTs should arrange multiplex testing through local arrangements, including UKHSA public health laboratories or other commissioned services as appropriate to their local context. This will provide useful information for the management of these outbreaks as well as important intelligence for surveillance purposes.

Sampling should be undertaken as close as possible to illness onset (and no more than 7 days after onset). Those aged 11 years or under should be swabbed by a parent or guardian, while self-swabbing can be considered for children and young people 12 years and older. When considering multiplex testing, it is particularly useful if swabs can be returned via a central point to the diagnostic laboratory (as per local arrangements) so that transport of samples can be co-ordinated and the timeline for reporting of the overall results can be estimated. This could be via school reception or an agreed local NHS service.

Further advice on testing during outbreaks can be sought from the regional public health laboratory in the first instance. Local arrangements should be made with the regional laboratory for rapid turnaround of testing in response to outbreak investigation.

Expert epidemiological advice can be sought from the national influenza team, for example if wider testing is being considered to better understand the epidemiology of the outbreak.

During the winter, there may be simultaneous circulation of multiple pathogens within a single ARI outbreak.

6.3 Declaration of outbreak

Local HPT risk assessment as above will inform the decision as to whether the situation meets the definition of an outbreak (see section 4. ‘Definitions’).

Once an outbreak has been declared, local stakeholders (for example, directors of public health and local authority public health teams) should be informed as per local protocols and in line with the overall public health risk assessment. Where necessary (for example complex situations, with large numbers of cases) an outbreak control team (OCT) should be considered.

Consider the need for an OCT if:

• there has been a death at the school or college or multiple hospitalisations
• there are a large number of children vulnerable to severe disease
• there are a high number of cases
• the outbreak has been ongoing despite usual control measures
• there are concerns on the safe running of the school
• there are other factors that require multi-agency coordination and decision making

7. Outbreak control and communications

7.1 Infection control

IPC measures (where appropriate) should be implemented according to Health protection in schools and childcare.

7.2 Case management

Cases with mild symptoms such as a runny nose, sore throat, or slight cough, who are otherwise well, can continue to attend their education setting unless directed otherwise by the HPT. There may be lower thresholds for self-isolation or staying away from the setting in an ARI outbreak.

Cases who are unwell and have a high temperature should stay at home and avoid contact with other people, where they can. They can go back to school, college or childcare when they no longer have a high temperature and they are well enough to attend.

Symptoms such as cough and anosmia can persist for weeks after the acute infectious episode and should not prevent return to school.

Those testing positive for COVID-19 should follow national guidance on preventing spread to others.

7.3 Communications

If applicable, the school should ensure effective communication to:

• raise awareness among parents and guardians of the ARI outbreak – this is often achieved through a written communication agreed and disseminated by the school through its existing mechanisms
• provide consistent messaging that symptomatic children as described above should not attend school until they are afebrile and well enough to attend
• publicise clear respiratory hygiene measures within the school such as regular handwashing and ‘Catch It, Bin It, Kill It’ type messages

7.4 Influenza antiviral treatment and prophylaxis

Influenza antiviral treatment may be recommended for certain children during confirmed influenza outbreaks. Any decision to recommend influenza antiviral treatment:

• must be based on local risk assessment
• must be communicated clearly in outbreak-related communications to parents and guardians

Where influenza antiviral treatment is recommended, the local HPT may advise that exposed children in clinical risk groups (see Green Book chapter 19) who have not received seasonal influenza vaccination, or who received this vaccination less than 14 days prior to exposure, or may not have responded due to immunosuppression, should be considered for antiviral prophylaxis with oseltamivir by a hospital health professional or paediatrician – this advice relates to exposure within the last 48 hours (or within 36 hours for zanamivir) if this risk assessment is likely to be feasible within this time period.

Symptomatic children in clinical risk groups may be considered for antiviral treatment with oseltamivir, ideally within 48 hours of onset (or within 36 hours for zanamivir) in accordance with national guidance on influenza treatment and prophylaxis using anti-viral agents.

Outside of the Chief Medical Officer (CMO)-defined influenza season, antivirals cannot be prescribed on the normal community prescription form (FP10 or electronic equivalent) but need to be prescribed on a patient specific direction (PSD) (or could be supplied through a patient group direction, PGD, for large groups). Local plans should be agreed in advance between the NHS Integrated Care System (ICS), the HPT and other relevant partners on how best to implement this and arrangements clearly communicated to all parties prior to the start of the influenza season.

When the number of children in clinical risk groups is thought to form a relatively small proportion of the school’s pupils and the CMO has not advised that antivirals may be prescribed in primary care, it may be possible for these to be prescribed by a hospital health professional such as a paediatrician. Consider writing a letter to parents or guardians to explain the situation. An alternative would be to telephone the parents directly, if this would expedite access to antivirals within the recommended time periods for starting prophylaxis (within 36 to 48 hours of exposure depending on the individual medicine).

Parents or guardians with an exposed child in a clinical risk group should then contact their specialist clinician looking after their child or be referred to paediatric Accident and Emergency (A&E) department to be considered for antivirals – the local HPT may need to facilitate this according to local processes. This is the preferable approach, as these health professionals will have the relevant medical history for these children.

If antivirals are indicated, the local HPT should discuss procurement with the local NHS commissioner as soon as possible.

The need for antivirals among staff in clinical risk groups should be addressed in a similar way to that outlined for children above.

7.5 Influenza vaccination

In a confirmed influenza outbreak, consideration should be given to wider influenza vaccination throughout the educational setting, especially in settings with low uptake of influenza vaccination to date.

Influenza vaccination does not provide post-exposure prophylaxis. Two weeks are required for the immune response to vaccination to develop and so this is unlikely to prevent secondary and tertiary cases. However, if an influenza outbreak is occurring in a school where influenza vaccination has yet to be delivered, consider whether the vaccination session can be brought forward. This may help to prevent further transmission and shorten the duration of the outbreak, though HPTs should be cognisant of the challenges school-aged immunisation services have in scheduling and rescheduling sessions during the autumn vaccination campaign. Local NHS services may also have catch up clinics that parents could be signposted to if the school vaccination session has finished and their child is not yet vaccinated.

7.6 Follow-up and end of outbreak restrictions

Follow-up of individual outbreaks in schools should be undertaken according to local HPT processes.

Schools should be advised when to call the HPT, especially if there are any features of concern (such as those outlined for calling an OCT, see section 6.3. ‘Declaration of outbreak’).

The end of a test-confirmed influenza outbreak is defined as a single 5-day period following symptom onset of the last outbreak case, during which there are no new cases of ILI or confirmed influenza cases within the same school group.

The end of an ARI outbreak where influenza has not been confirmed by laboratory testing is defined as a single 5-day period following symptom onset of the last outbreak case, during which there are no new cases of ARI within the same school group. It is expected that ARI cases continue to arise in children throughout the school year, associated with a range of viral infections, as part of normal background rates.

Schools should be encouraged to maintain vigilance beyond the outbreak period and to contact the HPT if further concerns arise.

7.7 Temporary closure

It is anticipated that temporary closure of a school for public health reasons is likely to be a very infrequent measure for ARI outbreaks. Any enquiry about potential closures on public health grounds should be discussed by the school management team directly with the local UKHSA HPT in the first instance and school closure on public health grounds should be an OCT decision. Any decision to temporarily close for business continuity reasons, such as staff shortages, is a decision for the school management and local education authority, where applicable; however, it should be made clear to parents, guardians and staff that this decision has not been made on public health grounds.

7.8 Recording and surveillance

Outbreak reporting forms are not required for routine surveillance. Probable and confirmed outbreak surveillance data is obtained from HPZone or successor case and incident management systems. Information about acute ARI outbreaks in schools where the causative agent is identified should, in the first instance, be recorded on HPZone as per routine practice and data captured in the HPZone metrics when possible rather than as free text. The equivalent processes should be followed in successor systems. These data will then be extracted by the national surveillance team and reported on in the weekly surveillance reports.

Appendix 1. Additional considerations for residential educational settings

Transmission of respiratory viruses can be rapid in boarding schools and other residential educational settings, with the potential for high attack rates.

In these closed settings:

• transmission may vary according to individual boarding houses, so extra sampling of symptomatic persons in different boarding houses should be considered, following discussion with the regional public health laboratory
• ensure a consistent case definition is used with healthcare providers and a consistent method of monitoring number of cases is agreed from the outset
• clarify seasonal influenza vaccination provision and uptake among pupils
• if the school hosts international pupils, determine if onset has occurred within 2 to 3 days of arrival from a foreign country
• consider if public health exclusion from the school is possible – if this is not possible, then advise restriction within residential accommodation until they no longer have a high temperature and feel well enough to attend school.
• primary care health professionals who have assessed suspected or confirmed cases and are referring the patient to hospital for further assessment or management should advise the hospital that the case-patient is part of a suspected outbreak, so that appropriate IPC measures can be taken
• maintain awareness of the possibility of other respiratory infections and consider using locally agreed arrangements to swab up to 5 symptomatic cases in the inter-seasonal period or early in the influenza season, to inform risk assessment and outbreak management

Appendix 2. Additional considerations for special school settings

Special educational needs and disabilities (SEND) include 4 different areas of need, including:

• communicating and interacting
• cognition and learning
• social, emotional and mental health difficulties
• sensory or physical needs

Many children and young people with SEND have one or more conditions which place them at increased risk of severe influenza infection and should be identified as members of clinical risk groups. Examples of relevant conditions include, but are not limited to, cerebral palsy, hydrocephalus and neuromuscular diseases (for example, spinal muscular atrophy, Duchenne muscular dystrophy).

As a result, an influenza outbreak in a special school setting, where a significant proportion of the learners are members of clinical risk groups, has the potential for serious clinical illness.

Rapid public health intervention following a thorough risk assessment is therefore justified in relation to outbreaks in such settings. Confirmation of the causative organism by rapidly testing recent symptomatic cases for COVID-19, influenza and other respiratory viruses can be useful to inform management. Advice on consideration of antivirals where influenza is strongly suspected or laboratory confirmed can be obtained from the UKHSA influenza team, as required.

In order to support rapid public health action, when the CMO has advised that seasonal influenza is circulating in the community, local NHS commissioners should determine if central distribution of antiviral treatment or prophylaxis in confirmed influenza outbreaks would be more practicable than individual children’s families contacting their specialist health professionals or paediatric A&E. When influenza is not circulating, the local HPT will need to work with NHS commissioners to identify alternative mechanisms for accessing and prescribing antivirals for treatment or prophylaxis in a timely way.

Individual children with special needs who attend other settings (for example mainstream schools) should receive information as outlined in the control measures section. Centralised prescribing and distribution may not be required, as there may be a smaller number of children in clinical risk groups in these settings.

Contact

For queries relating to this document, please contact respiratory.lead@phe.gov.uk