Influenza

Key Messages

  • Immunization against seasonal influenza has been shown to reduce the number of hospitalizations and deaths.
  • In Ontario, laboratory testing for influenza is only available for hospitalized patients or in the context of institutional outbreaks. The specimen of choice for diagnosing influenza virus is the nasopharyngeal (NP) swab taken within the first four days of illness.
  • Laboratory testing for influenza is not available to community-based healthcare providers in Ontario. Empiric treatment with antivirals is recommended by AMMI in suspected influenza cases who are at high-risk of influenza complications or with progressive, severe, or complicated illness.
Local Epidemiology

To obtain the latest statistics on influenza:

To obtain the latest statistics on other circulating respiratory viruses:

  • In Ottawa, Ontario, and Canada: the Respiratory Virus Detection Surveillance System (published weekly on Wednesday). Ottawa-specific data is presented in Table 1 rows “Ottawa P.H.L.” and “CHEO - Ottawa”. This report also provides Ontario-level data in the Table 1 row “Province of Ontario”, and national data in row “CANADA”.

NOTE: the incidence of influenza and other respiratory viruses in the community is greatly under-reported because the majority of persons with influenza-like illness (ILI) do not seek medical care, and do not undergo (are not eligible for) laboratory testing.

Signs and Symptoms

Symptoms: include, but are not limited to:

  • New or worsening cough
  • Shortness of breath
  • Fever (may be absent in the elderly or immunocompromised)
  • Sore throat
  • Headache
  • Myalgia
  • Lethargy
  • Gastrointestinal symptoms (e.g., nausea, vomiting, diarrhea) in some children

Duration of illness: In most people, illness resolves within five to seven days. Complications are most common in the very young and the elderly; death is most common in the elderly.

Patient resource: How to differentiate influenza from the common cold

Infection Prevention and Control (IPAC) Measures

Key IPAC measure to prevent transmission in clinical office settings:

  • Provide self-screening signage at the entrance to the clinic
  • Triage persons with cough & fever into a separate waiting room (or exam room) or keep at least 2 metres away from other clients; ask them to wear a surgical mask if they have a cough.
  • Make 70% alcohol-based hand-rub (ABHR), masks and tissues available in the waiting room.
  • Clean and disinfect horizontal surfaces in patient care areas between patients.
  • Clean and disinfect high-touch surfaces frequently throughout the day.
  • Make personal protective equipment (PPE: gloves, face shields, surgical masks) and ABHR available for staff at point of care.
  • Emphasize to staff the importance of hand hygiene including when leaving exam rooms.
  • Recommend that all clinical office staff receive their seasonal influenza immunization as soon as it is available (i.e., before the start of the influenza season)

Mode of transmission:

Influenza virus particles are easily spread by contact and droplets which are released from infected persons when they sneeze, cough, or talk.

Period of communicability:

People become infectious 24 hours prior to onset of symptoms; viral shedding in nasal secretions usually peaks during the first three days of illness and ceases within seven days but can be prolonged in young children, the elderly and those who are immunocompromised.

For more information about IPAC:

Guidelines for all healthcare settings: 

Diagnosis / Laboratory testing
  • In Ontario, laboratory testing for influenza is only available for hospitalized patients or in the context of institutional outbreaks.
  • Laboratory testing for influenza is not available to community-based healthcare providers in Ontario, except through the Canadian Sentinel Practitioner Surveillance Network. Join this network to receive timely results about your patients’ diagnoses and to help inform Canada’s and the WHO’s influenza vaccination policies.
an NP swab
  • The specimen of choice for diagnosing influenza virus is the viral nasopharyngeal (NP) swab taken within the first four days of illness.
  • Treat suspected influenza infection empirically with antivirals, especially in patients at high-risk of influenza complications.
Reporting to Public Health

Report all suspected and confirmed respiratory outbreaks in institutions (e.g., hospitals, LTCH, retirement homes, shelters) to Ottawa Public Health by calling 613-580-2424 extension 26325. After hours, on weekends, or holidays: call 3-1-1.

Please report all laboratory-confirmed influenza cases to Ottawa Public Health by calling: 613-580-2424, extension 24224 or fax 613-580-9640. After hours, on weekends, or holidays: call 3-1-1.

Management of Patients

Most people will fully recover from influenza without medical intervention or antiviral treatment. Influenza management focuses on rest, fluid intake, and symptom management if necessary. Symptomatic persons should be encouraged to remain at home (avoid school/work and social events) to avoid transmitting influenza to others, especially those at high risk of complications.

Who is recommended to receive antivirals?

Antiviral treatment with oseltamivir (Tamiflu®) or zanamivir (Relenza®) is recommended by AMMI  for influenza-like illness (ILI) if:

  • the illness is progressive, severe, or complicated, or
  • the patient is at high risk of influenza-related complications, or
  • the patient is hospitalized, or
  • the individual is involved in an institutional influenza outbreak.

People at high risk of influenza-related complications or hospitalization are:

  • Pregnant women.
  • People 65 years of age and older.
  • Children under 5 years of age.
  • Adults and children with the following chronic health conditions:
    • cardiac or pulmonary disorders (including bronchopulmonary dysplasia, cystic fibrosis and asthma);
    • diabetes mellitus and other metabolic diseases;
    • cancer, immune compromising conditions (due to underlying disease, therapy or both);
    • renal disease;
    • anemia or hemoglobinopathy;
    • neurologic or neurodevelopment conditions;
    • morbid obesity (body mass index [BMI] of 40 and over);
    • children and adolescents (age 6 months to 18 years) undergoing treatment for long periods with acetylsalicylic acid, because of the potential increase of Reye’s syndrome associated with influenza.
    • People of any age who are residents of nursing homes and other chronic care facilities.
    • Indigenous peoples.

For those with influenza, treatment with oseltamivir (Tamiflu®) or zanamivir (Relenza®) shortens the duration of the symptoms and reduces the risk of complications.

When to prescribe antivirals:

  • When influenza is circulating in the community, laboratory confirmation of influenza is not needed to begin antiviral treatment. Waiting for laboratory confirmation would delay initiation of therapy.
  • Ideally, antiviral treatment should begin as soon as possible within 48 hours of symptom onset.
  • For those at high risk for influenza complications, antiviral treatment can be considered even if more than 48 hours have passed since symptom onset.
  • For individuals with moderate, progressive, severe or complicated influenza-like illness, such as individuals who are hospitalized with influenza-like illness, use of antiviral medication is recommended, regardless of time from symptom onset.
How to prescribe antivirals for influenza:

 

Oseltamivir (Tamiflu®)

Zanamivir (Relenza®)

(5 mg per inhalation)

Dosage for treatment

75 mg twice daily for 5 days for adults.

See AMMI guideline for pediatric dosing.

Dose adjustments may be needed if person is known to have renal impairment; see AMMI guidelines.

2 inhalations twice daily (approximately 12 hours apart) for 5 days.

Dosage for prophylaxis (e.g., in the context of an institutional outbreak)

75 mg daily for 10 days for adults (or in an outbreak, until the outbreak is declared over).

See AMMI guidelines for pediatric dosing.

Dose adjustments may be needed if person is known to have renal impairment; see AMMI guidelines.

2 inhalations twice daily (approximately 12 hours apart) for 5 days.

Age authorized for use

1 year of age and older.

Can be considered on a case-by-case basis for those younger than 1 year of age.

7 years of age and over.

Contraindications

None.

See product monograph for additional details.

Underlying respiratory condition such as chronic obstructive pulmonary disease or asthma.

See product monograph for additional details.

PDF version

Source: Public Health Ontario (2017). Antiviral medications for influenza: Information for health care providers. Retrieved from: http://www.publichealthontario.ca/en/eRepository/Antiviral_Medication_Influenza_Fact_Sheet.pdf 

More resources on how to prescribe antivirals for influenza:

Management of Institutional Outbreaks

Report all suspected and confirmed respiratory outbreaks in institutions (e.g., hospitals, LTCH, retirement homes, shelters) to Ottawa Public Health by calling 613-580-2424 ex 26325 or call 3-1-1 during evenings, weekends and holidays. Ottawa Public Health will assist you with outbreak management.

Access OPH resources on Respiratory Outbreaks in Long-Term Care Facilities and Retirement Homes, including line lists, instructions for collecting NP swab, antiviral recommendations for facility residents during an outbreak, etc.

Other resources for outbreak management:

Immunization
  • Immunization is the most effective way to prevent influenza and influenza-related complications, hospitalization, and deaths.
  • Annual vaccination is required because influenza viruses change often; the specific strains in the vaccine are reviewed each year by WHO and updated as necessary so that there is the greatest probability of matching circulating viruses.

Who is recommended to be immunized against influenza?

NACI recommends that all individuals aged 6 months and older be immunized against influenza. As per the 2018-2019 NACI statement, influenza immunization is particularly recommended for the following groups:

  • People at high risk of influenza-related complications or hospitalization:
    • All pregnant women.
    • Adults and children with the following chronic health conditions:
      • cardiac or pulmonary disorders (including bronchopulmonary dysplasia, cystic fibrosis and asthma);
      • diabetes mellitus and other metabolic diseases;
      • cancer, immune compromising conditions (due to underlying disease, therapy or both);
      • renal disease;
      • anemia or hemoglobinopathy;
      • neurologic or neurodevelopment conditions;
      • morbid obesity (body mass index [BMI] of 40 and over);
      • children and adolescents (age 6 months to 18 years) undergoing treatment for long periods with acetylsalicylic acid, because of the potential increase of Reye’s syndrome associated with influenza.
      • People of any age who are residents of nursing homes and other chronic care facilities.
      • People 65 years of age and older.
      • All children 6 to 59 months of age.
      • Indigenous peoples.
  • People capable of transmitting influenza to those at high risk:
    • Health care and other care providers in facilities and community settings who, through their activities, are capable of transmitting influenza to those at high risk of influenza complications.
    • Household contacts (adults and children) of individuals at high risk of influenza-related complications (whether or not the individual at high risk has been immunized):
      • household contacts of individuals at high risk, as listed in the section above;
      • household contacts of infants under 6 months of age as these infants are at high risk of complications from influenza but cannot receive influenza vaccine;
      • members of a household expecting a newborn during the influenza season.
      • Those providing regular child care to children 59 months of age and under, whether in or out of the home.
      • Those who provide services within closed or relatively closed settings to persons at high risk (e.g., crew on a ship).
  • Others:
    • People who provide essential community services.
    • People in direct contact during culling operations with poultry infected with avian influenza.

How many vaccine doses are required?

Children 6 months to under 9 years of age receiving seasonal influenza vaccine for the first time in their life should be given two doses, with a minimum interval of four weeks between doses. All others require only one dose annually.

Contraindications to influenza immunization:

Influenza vaccine is contraindicated in:

  • Persons who have developed Guillain-Barré Syndrome (GBS) within six weeks of influenza vaccination.
  • Persons who have developed an anaphylactic reaction to a previous dose of influenza vaccine or to any of the vaccine’s components, with the exception of egg.
  • Egg-allergic individuals may be vaccinated against influenza without prior influenza vaccine skin test and with the full dose, irrespective of a past severe reaction to egg, and without any extraordinary precautions, but ensuring that, as with all vaccine administration, immunizers be prepared with the necessary equipment, knowledge and skills to respond to a vaccine emergency at all times.
  • In situations of suspected hypersensitivity or non-anaphylactic allergy to a vaccine or its components, investigation is indicated which may involve immunization in a controlled setting. Consultation with an allergist is advised.

In addition, live-attenuated influenza vaccine (LAIV) (FluMist Quadrivalent®) is contraindicated in:

  • Children less than 24 months of age, due to increased risk of wheezing.
  • Individuals with severe asthma, as defined as currently on oral or high-dose inhaled glucocorticosteroids or active wheezing, or those with medically attended wheezing in the 7 days prior to the proposed date of immunization.
  • Children and adolescents 2 to 17 years of age currently receiving aspirin or aspirin-containing therapy because of the association of Reye’s syndrome with aspirin and wild-type influenza infection. It is recommended that aspirin-containing products in children less than 18 years of age be delayed for four weeks after receipt of live-attenuated influenza vaccine.
  • Pregnant women, because it is a live attenuated vaccine and there is a lack of safety data at this time. However, it is not contraindicated in breastfeeding mothers.
  • Persons with immune compromising conditions, due to underlying disease, therapy, or both, as the vaccine contains live attenuated virus.

Influenza vaccine products and ordering

Detailed information on publicly-funded influenza vaccines and vaccine ordering is available here.

Vaccine effectiveness:

  • Immunization is the most effective way to prevent influenza and influenza-related complications, hospitalization, and deaths.
  • Influenza vaccine effectiveness fluctuates year-to-year, depending on the match between the vaccine and the circulating influenza strain. Historical effectiveness estimates for Canada are available here.
  • Influenza vaccine effectiveness estimates are typically published after the peak of the influenza season has passed; immunization against seasonal influenza should not be delayed until vaccine effectiveness is known.
  • The Canadian Sentinel Practitioner Surveillance Network is the system to assess vaccine effectiveness in Canada. Join this network of sentinel practitioners to receive timely results about your patients’ diagnoses and to help inform Canada’s and the WHO’s influenza vaccination policies. 
Patient Information

Patient information is available at: OttawaPublicHealth.ca/Flu

Physician Resources

Surveillance reports:

IPAC:

Prescribing antivirals for influenza:

Outbreak management:

Immunization:

Contact Us

If you want to notify Ottawa Public Health about a suspected or confirmed respiratory outbreak in an institution, please contact us at 613-580-2424, extension 26325 or call 3-1-1 during evenings, weekends and holidays.

If you want to notify Ottawa Public Health about a laboratory-confirmed case of influenza, please contact us at 613-580-2424, extension 24224 or call 3-1-1 during evenings, weekends and holidays.

Contact Us