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Seasonal Influenza

Comments from Expert Advisory Committee and Key Points from 2019-2020fluvirusimage

  • The expert advisory group recommend that the Guidance on the use of antiviral agents for the treatment and prophylaxis of influenza 2019-2020 is consulted prior to making the final prescribing decision. It contains FAQ section and more detailed advice on various subgroups below.
  • Two antiviral medications are recommended for use in Ireland during the 2019-2020 influenza season: Oseltamivir (Tamiflu) and Zanamivir (Relenza).They are both antiviral neuraminidase inhibitors which have activity against seasonal influenza A and B.
  • Early antiviral treatment (within 36 -48 hours symptom onset) can reduce the risk of complications from influenza, e.g. otitis media in young children, pneumonia and respiratory failure, shorten duration of illness among acutely ill patients and reduce morbidity, including hospitalisation, and mortality among patients with severe infection.
  • 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
  • Uncomplicated influenza: Influenza presenting with fever, cough, sore throat, coryza, generalised symptoms (headache, malaise, myalgia, arthralgia), and sometimes gastrointestinal symptoms, but without any complications of influenza e.g. pneumonia, acute respiratory distress syndrome (ARDS).
  • Complicated influenza: Influenza requiring hospital admission and/or with symptoms and signs of lower respiratory tract infection (hypoxaemia, dyspnoea, lung infiltrate), central nervous system involvement and/or a significant exacerbation of an underlying medical condition.
  • 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. If you decide to treat use oseltamivir (PO).
  • 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.
  • Antivirals are 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)
  • 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. 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
  • Duration of treatment is usually 5 days
    • 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 outcome

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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:


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

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Defined Risk Groups for Antivirals - high risk complicated influenza

  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 is available

Residential Care Facilities

Patient Information

Advice for schools

Advice for churches

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Reviewed December 2019