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This guideline was initially written in response to the novel influenza H1N1 (swine flu) pandemic based on a number of other guidelines (including the Royal Children's Hospital Melbourne and the Ministry of Health). It has been adapted to be generic for influenza. For local detailed infection control information please see ADHB Policies and Guidelines Library 'Influenza and Influenza-like illness - prevention of in-hospital spread'.


Confirmed case
A confirmed case of influenza is defined as a person with laboratory confirmed influenza virus infection by one or more of the following tests:

  • real-time RT-PCR
  • viral culture (not currently being performed during pandemic)
  • four-fold rise in influenza virus specific neutralising antibodies

Probable case
A probable case of influenza is defined as a person with an influenza-like illness who has a strong epidemiological link to a confirmed case or defined cluster.

Close contact
Close contact is defined as having cared for, lived with, or had direct contact with respiratory secretions or bodily fluids of a probable or confirmed case.

Influenza-like illness

  • History of fever, chills, and sweating or clinically documented fever ≥38 °C,
  • cough or sore throat

Other features to consider in children include body aches, fatigue, tiredness and shortness of breath. Diarrhoea is a common symptom in children. Children with influenza can present with neurologic complications such as seizures or encephalopathy.

This is not all inclusive but will help with detection of children most likely to have influenza. Children under 12 months of age may have an even more non-specific illness. Surveillance studies suggest a low rate of influenza as a cause of acute wheezing illnesses in children.

When assessing children with Influenza-like illness consideration needs to be given to the possibility of influenza with a secondary bacterial infection (e.g. pneumococcal or staphylococcal disease) or bacterial infection with non-specific symptoms presenting similarly to influenza such as meningococcal disease. These possibilities would warrant use of appropriate antibiotics.

Co-morbidities, particularly immune suppression, chronic lung disease and morbid obesity, are risk factors for more serious disease.

Long term aspirin therapy is a risk factor for Reye's syndrome with influenza.

Emergency Department Assessment

Patient assessed to be well enough for discharge:

  • No viral investigations are needed unless the child is in a residential care facility such as Wilson Home or boarding school. Early in the influenza season viral swabs may be taken to establish aetiology.
  • Recommend patients stay at home until symptoms are resolved
  • Most patients do not require antiviral therapy. Oseltamivir should be given as treatment (see below) if patient has risk factors for more serious disease and if the seasonal influenza strains are known to be oseltamivir sensitive. These children should be discussed with the CED specialist on duty.
  • Prophylaxis (see below) should only be given to close family members if they have risk factors for serious disease. Symptomatic family members should not stay in the hospital or at Ronald McDonald house.

Unwell patient being admitted to hospital

Patient requires:

  • Respiratory isolation on ward
  • Appropriate sample taken (nasopharyngeal viral swab or aspirate) to confirm diagnosis and for cohorting purposes
  • Oseltamivir started if fulfils case definition (confirmed or probable) AND are either moderately/severely unwell or have co-morbidities AND the circulating strains are known to be oseltamivir-sensitive

Most children who are started on oseltamivir will also require initiation of antibiotics (see Starship pneumonia guideline). Bacterial superinfection can be a significant contribution to morbidity: - awareness and early initiation of antibiotics are required to minimise this.

Antiviral Medication

Oseltamivir (Tamiflu)

See separate Auckland Hospital guidelines for outpatient oseltamivir prescribing.

Please note that seasonal influenza may be oseltamivir-resistant and it should not be used in such cases. The resistance pattern of circulating strains will be known early in each season or epidemic.

Oseltamivir is licensed for treatment and prophylaxis of children over one year of age. It has not been widely studied in children under 12 months of age, but can be considered for hospitalised patient with risk factors. Clinical judgement should be used weighing risks of disease against unknown risks of oseltamivir.

There is even less information about use of oseltamivir in infants under 3 months of age. Discuss with Paediatric Infectious Disease specialist on call if considering this.

Oseltamivir may reduce duration of illness, severity of illness and duration of viral shedding. Best results occur if treatment begins within 48-72 hours of symptoms starting.

Cases where oseltamivir use is appropriate include:

  • Symptomatic severe influenza-like illness
  • Pregnancy
  • Immuno-compromised
  • CHF (severe/poorly controlled)
  • Chronic Respiratory Disease (severe)
  • Asthma (severe + steroids)
  • Renal haemodialysis or CAPD
  • Any other condition putting patient at high risk e.g. poorly controlled diabetes, obesity, on Clozapine
  • Nursing home /chronic care facility resident
  • Health / other care providers in facilities or community settings

Oseltamivir (Tamiflu) Dosing

For patients who cannot swallow capsules, Tamiflu® oral suspension is the preferred formulation. The suspension is available as 12mg/ml. Doses in this guideline for children < 1 year are based on 2 to 3mg/kg per dose and have been adjusted to account for the strength of the suspension.

The bottle comes with a dispenser marked for 30, 45 & 60 mg which should not be used for doses less than 30mg. Provide patients with an oral syringe instead (e.g. 3 ml or 5 ml) to measure doses and give instructions in mL.

If the oral suspension is not available, dissolve contents of capsule in 5 ml water using graduated syringe; mix well and withdraw required dose. May be mixed with sweetened liquids/ food to mask the bitter taste of the medication.

Children < 1 year

Patient weight Treatment Dosing
≤ 3 kg  6mg twice daily for 5 days
 >3 to 4 kg  9mg twice daily for 5 days
 >4 to 6 kg  12mg twice daily for 5 days
 >6 to 9 kg  18mg twice daily for 5 days
 >9 to 12 kg  24mg twice daily for 5 days
 >12 to 14 kg  30mg twice daily for 5 days

Children > 1 year

Patient weight Treatment Dosing 
 < 15 kg  30 mg twice daily for 5 days
 15 to 23 kg  45 mg twice daily for 5 days 
 23 to 40 kg  60 mg twice daily for 5 days

Adolescents and children > 40kg

Patient weight  Treatment Dosing 
 >40 kg  75 mg twice daily for 5 days


  • For post-exposure prophylaxis use the same dose but ONCE daily for 10 days
  • Refer to product datasheet for further prescribing information.
  • Adjust dosing for renal failure and dialysis. Discuss with Paediatric Renal team or Paediatric Pharmacist.
  • Give doses with food to minimise GI upset. If vomiting occurs within 30 minutes of administration a repeat dose should be given.

Zanamivir (Relenza)

Zanamavir is another neuraminidase inhibitor, delivered as an inhaled powder by rotadisk. It is active against influenza A and B, sometimes even for strains resistant to Oseltamivir. It is licensed for children >5years. Treatment dose is 2 x 5mg inhalations twice daily for 5 days; prophylaxis dose is 2x 5mg inhalations once daily for 10 days.

Infection Control Issues

See also ADHB document 'Influenza and Influenza-like illness - prevention of in-hospital spread' under the policies and guidelines library

Careful hand hygiene and social distancing remain the most effective way to reduce the spread of infection

There is no consensus on duration of isolation in hospital. The decision will be influenced by the presence of underlying disease (e.g. chronic respiratory disease or immunosuppression), patient age and the use of antiviral medication.

  • 5 years with no co-morbidities, immunosuppression or underlying significant respiratory disease (excluding asthma): Take out of isolation after 5 days of oseltamivir or if no antiviral taken after 7 days of illness with resolution of symptoms
  • < 5 years with no co-morbidities, immunosuppression or underlying significant respiratory disease (excluding asthma): Take out of isolation after 5 days of oseltamivir or if no antiviral taken after 10 days of illness with resolution of symptoms. Younger children are believed to excrete virus for longer periods.
  • If immunosuppressed or significant respiratory disease eg bronchiectasis remain in isolation for length of hospital stay. Can be discussed with Paediatric Infectious Disease specialist on call.

Staff exposure

See ADHB policicies and guidelines library for 'Influenza and Influenza-like illness - prevention of in-hospital spread'.

Information for Families

See Kidshealth factsheet on flu (influenza) (


Medsafe Data sheet (Tamiflu®) [Datasheet online] Roche Products.

Royal Children's Hospital Melbourne, Oseltamivir doses in children Version 5, 1 June 2009

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Document Control

  • Date last published: 01 July 2012
  • Document type: Clinical Guideline
  • Services responsible: Paediatric Infectious Diseases
  • Author(s): Elizabeth Wilson, Lesley Voss
  • Editor: Greg Williams
  • Review frequency: 2 years

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