January 10, 2017

Information for Family Physicians on Influenza

Family physicians see the majority of patients presenting to the health-care system with symptoms consistent with influenza. The flu season has begun in Ontario and is anticipated to peak over the coming weeks. There are several resources available through Public Health Ontario (PHO) which many will find helpful.  

General information and a map for tracking influenza activity in Ontario is available on PHO's Influenza information page. To know the activity of influenza and influenza-like illness (ILI) in your area, you can refer to the "influenza like illness" map which is updated regularly.

Who should be swabbed for testing for influenza?: First, it is important to know that the PCR testing for influenza (the nasopharyngeal swab sent to public health) should be used only in those who are at high risk of complications from respiratory viral infections.

The Public Health guidance document regarding testing with the "multiplex respiratory viral PCR" test can be found here. An excerpt from the guideline states the following:
"To ensure the highest quality testing of patients requiring these results for clinical management, PHO’s new respiratory viral testing algorithm and testing will be used for:

  • Patients admitted to hospital
  • Patients presenting to the emergency department
  • Patients undergoing bronchoalveolar lavage (BAL)
  • High risk patients in outpatient settings including children <5 years and adults 65 years or older, and patients with underlying chronic conditions (See Table for a complete list of high risk conditions)
  • Outbreak investigations"

Respiratory viral testing in non-high risk ambulatory patients is of minimal clinical value for this patient group and will no longer be available at PHO.
To assist with the assessment and management of non-high risk ambulatory patients, clinicians are encouraged to keep up-to-date on respiratory viruses and select bacterial pathogens circulating in Ontario by regularly reviewing PHO’s Ontario Respiratory Pathogen Bulletin (ORPB) (produced weekly from November to April and biweekly from May to October). Findings are analyzed by all patient settings, including ambulatory settings, as well as by local Public Health Unit.

How to do a nasopharyngeal swab and how to complete the requisition: Here is some information about completing the requisition and a YouTube link with information on how to do the nasopharyngeal swab.

Who is at risk of the complications of influenza? The Association of Medical Microbiology and Infectious Disease (AMMI) Canada guidelines state that patients at high risk for respiratory viral infection complications include the following patients: 

  • Asthma and other chronic pulmonary disease, including bronchopulmonary dysplasia, cystic fibrosis, chronic bronchitis and emphysema
  • Cardiovascular disease (excluding isolated hypertension; including congenital and acquired heart disease such as congestive heart failure and symptomatic coronary artery disease)
  • Malignancy
  • Chronic renal insufficiency
  • Diabetes mellitus and other metabolic diseases
  • Hemoglobinopathies such as sickle cell disease
  • Immunosuppression or immunodeficiency due to disease (e.g., HIV infection, especially if CD4 is <200×106/L), or iatrogenic, due to medication
  • Neurologic disease and neurodevelopmental disorders that compromise handling of respiratory secretions (cognitive dysfunction, spinal cord injury, seizure disorders, neuromuscular disorders, cerebral palsy, metabolic disorders)
  • Children younger than 5 years of age*
  • Individuals 65 years of age or older
  • People of any age who are residents of nursing homes or other chronic care facilities
  • Pregnant women and women up to 4 weeks post-partum regardless of how the pregnancy ended
  • Individuals <18 years of age who are on chronic aspirin therapy
  • Obesity with a BMI >40 or a BMI >3 z-scores above the mean for age and gender
  • Aboriginal peoples
    * Children who are two through four years of age also have a higher rate of complications compared to older children; however, the risk for these children is lower than the risk for children younger than two years of age.

Who should be considered for treatment with antivirals?
According to the PHO guideline document Antiviral medications for influenza: Information for health care providers influenza antiviral medications are recommended for the:

  • Treatment of moderate, progressive, severe or complicated influenza, such as individuals who are hospitalized with influenza-like illness;
  • Treatment of those at high risk for complications of influenza, such as children less than 5 years of age, adults 65 year of age and over, and those with underlying medical conditions;
  • Treatment and prevention in influenza outbreaks in institutional settings. 

The doses of oseltamivir and zanamivir are in the above linked document. This document includes dosing for children as well as renal dosing, and dosing for prophylaxis which is different than the treatment dosing. 

In 2015 Tools for Practice completed an evidence summary identifying that the evidence base for use of antivirals in otherwise healthy individuals is very poor. There may be a half day of symptoms prevented but no decrease in complications or hospitalizations.  

In December 2016, Tools for Practice did a summary of the evidence for prophylaxis and that summary including numbers needed to treat is here.      

And what about infection control in our offices? Finally, and importantly there is much that can be done within offices to prevent the transmission of infection. The document, Annex B: Best Practices for Prevention of Transmission of Acute Respiratory Infection n All Health Care Settings, provides some guidance for office practices regarding identifying patients with febrile respiratory illnesses (FRI), like ILI, mask use for patients who are symptomatic, hand hygiene and room and equipment cleaning after patients with FRI or ILI have been in an examination room.        

We hope that this information is helpful to you and your staff this influenza season. Please let us know if there are other pieces of information that you would find helpful.

Many thanks to PHO's Dr. Brian Schwartz and Dr. Doug Sider for their support and guidance in compiling these resources and for their support of our work in primary care in the community.