Seasonal Influenza

Comments from Expert Advisory Committee and Key Points from 2018-2019fluvirusimage

  • When influenza is circulating in the community, antiviral therapy should be considered for influenza-like illness in patients who are very ill or who are in recognised risk groups for severe influenza. Information will be issued to GPs when influenza rates increase and antivirals are recommended. See weekly influenza activity reports
  • Previously healthy people (excluding pregnant women ) do not need antiviral treatment unless the clinician feels the patient is very ill or is at serious risk of developing complications from influenza. Symptomatic treatment is the preferred option.
  • Patients who remain unwell after 5 days antiviral treatment need careful clinical assessment. They may have a secondary bacterial infection, or be infected with an antiviral-resistant influenza strain. Specialist consultation is advised especially in immunocompromised or multi-morbidity. There is no evidence that prolonged courses ( > 5 days) of antiviral treatment improve outcomes.Click here to view full information from HPSC
    The expert advisory group recommend that these HPSC guidelines are consulted prior to making the final prescribing decision.
  • At risk population: prescribe oseltamivir (PO). Do not wait for laboratory confirmation. Treatment should be started as soon as possible, ideally within 48 hours of onset. There is evidence that treatment may reduce the risk of severe illness up to five days after onset. Severely immunosuppressed patients: prescribe oseltamivir (PO) Rapid emergence of oseltamivir resistance on treatment has been described in these patients and they should be monitored closely. Resistance to oseltamivir has been described in infections from influenza A (H1N1) pdm09 subtype but not in those from influenza A (H3) to date (source: NVRL). However, resistance is uncommon.
  • Clinicians may consider the use of zanamivir (unlicensed but available inhaler) as first line therapy in immunosuppressed patients with suspected or confirmed influenza A (H1N1) pdm09 based on clinical judgement.
  • Suspected or confirmed oseltamivir resistant influenza in a patient who requires treatment: Zanamivir (unlicensed but available inhaler) 10 mg (2 inhalations) bd. Treatment should be started as soon as possible and ideally within 36 hours of symptom onset.
    Expert advisory group recommend seeking expert advice if considering switch to Zanamivir in immunocompromised
  • Guidance on the use of antiviral agents for the treatment and prophylaxis of influenza,2018-2019
  • New IV antiviral Peramivir may become available during the current influenza season

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Table 1: Antiviral Treatment dosages and schedules for treatment of Children, Adults, Pregnant and immunocompromisedflu table 1 treatment 2019

Available products:

  • Oseltamivir 30mg, 45mg and 75mg caps
  • Under 1 year olds, oseltamivir powder for oral suspension 6mg/ml.
  • Zanamivir powder for inhalation 5mg per dose. (Not licensed but available)
  • Children over one and adults with swallowing difficulties, and those receiving nasogastric oseltamivir, should use capsules which are opened into an appropriate sugary liquid as oseltamivir has a very bitter taste. If the powder for suspension is used for children over one year of age and/or adults, there may not be adequate quantities of the powder for suspension to meet demand for the under one year age group. It is important that the powder for suspension is reserved for the less than one year age group.’
  • Product information for Zanamivir (not licensed but available)
  • Product information for Oseltamivir


Chemoprophylaxis should be reserved for those in at risk groups who have had recent close contact with a person with influenza or influenza-like illness in the same household or residential setting. Previous influenza vaccination does not preclude the use of post exposure prophylaxis, in particular where localised outbreaks occur in residential care facilities. Click here for more information from the HPSC

Influenza Algorithm for Primary Care

Click here or on the image below for the link to the influenza algorithm


See guidance on dosing in children for quick reference dosage/weight guide

Table 2: Antiviral dosage and schedules for chemoprophylaxis

flu table 2 treatment 2019

Footnote 10: If a child is younger than 3 months old, use of oseltamivir for chemoprophylaxis is not recommended unless situation is judged critical due to limited data in this age group

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Defined Risk Groups for Antivirals

  1. Age 65 years and over
  2. Pregnancy (including up to two weeks post partum), see below.
  3. Children aged <2 years of age
  4. Chronic respiratory disease including those on medication for asthma
  5. Chronic heart, kidney, liver or neurological disease
  6. Diabetes mellitus
  7. Haemoglobinopathies
  8. Immunosuppression (whether due to treatment or disease e.g. HIV)
  9. Morbid obesity (BMI ≥40)
  10. Those with any condition that can compromise respiratory function (e.g. cognitive dysfunction, spinal cord injury, seizure, or other neuromuscular disorder), especially those attending special schools/day centres
  11. Down Syndrome
  12. Children with moderate to severe neurodevelopmental disorders such as cerebral palsy and intellectual disability
  13. Residents of nursing homes or other residential care facilities

The full HPSC Antiviral Treatment of Influenza Guidelines are available here.

All pregnant women with influenza like illness should seek medical advice

  • Antivirals have been recommended for pregnant women due to the adverse clinical outcomes that have been observed for influenza in this group.
  • Oseltamivir remains the first line option for the vast majority of pregnant women with influenza, including during seasons that are dominated by influenza A (H1N1)
  • For pregnant women who meet additional criteria for requiring zanamivir first line, further assessment (i.e. rapid diagnostics) and antiviral treatment should be discussed with a local infection specialist.
  • Oseltamivir is generally well tolerated in patients with influenza, but side effects can occur. There are no data suggesting tolerability differs between pregnant and non-pregnant adults
  • Recent studies suggest there is no evidence of harm in pregnant women treated with oseltamivir or zanamivir (not licensed but available)
  • Chemoprophylaxis is not routinely recommended for pregnant women. However, clinical judgement may be exercised in individual cases if the benefit outweighs the risk.
  • Click here for the HPSC influenza advice during pregnancy

Residential Care Facilities

Patient Information

Advice for schools

Advice for churches

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Reviewed December 2018