Influenza Virus

Diagnosis of Influenza

Accurate Diagnosis of Influenza is Challenging…

  • It can be difficult to distinguish among the many types of "common cold" viruses, bacteria and influenza viruses, because many of these pathogens can cause non-specific respiratory and somatic symptoms5
  • Serious bacterial infections may begin with influenza–like symptoms or may coexist with or occur as complications during the course of influenza

…Especially for Children

  • Influenza is responsible for substantial morbidity in children and increases the need for health care, including hospitalization 6
  • A prospective, population-based study showed that:
    • 83% of children were misdiagnosed in the outpatient setting 7
    • 72% of children were misdiagnosed in the inpatient setting 7

Early and Accurate Diagnosis is Critical

  • Vaccine effectiveness varies. Therefore, influenza should not be ruled out in the differential diagnosis.
    • 17-59 years of age*: 70% to 90% effective
    • 50-64 years of age*: 52% effective
    • 58-104 years of age†: 17% to 53% effective
    * Vaccine efficacy based on measurement of immune response.
    † Vaccine efficacy based on measurement of antibody response.
  • Rapid diagnostic tests are available that can detect influenza viruses in 30 minutes.
  • Early diagnosis of influenza can reduce the inappropriate use of antibiotics and provide the option of using antiviral therapy such as TAMIFLU 3
  • To be effective at treating and reducing duration of influenza symptoms, TAMIFLU must be administered within 12 to 48 hours of symptoms onset 1

Improve Your Influenza Diagnoses

The identification of influenza is improved when clinicians are aware that influenza virus is present in their area. 5 Use the Flu Tracker to find out where the flu is circulating nationwide.

Know Influenza Signs and Symptoms vs. Common Cold 5

     
  Signs & Symptoms Influenza Common Cold  
     
  Onset Sudden Gradual  
  Fever* Common: lasting 3-4 days Rare  
  Cough Dry; can become severe Hacking; mild  
  Headache Prominent Rare  
  Muscle/joint aches, pain Unusual; often severe Slight  
  Fatigue and weakness Can last up to 2 weeks Very mild  
  Extreme exhaustion Early and prominent Never  
  Chest discomfort Common Mild/moderate  
  Stuffy nose Sometimes Common  
  Sneezing Sometimes Usually  
  Sore throat Sometimes Common  

* For many people aged ≥ 65 years or who have chronic illnesses, the risk and severity of influenza infection is magnified; however, flu-induced fever in these individuals may be minimal or even absent.

Influenza Resources

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Important Safety Information

Indications

TAMIFLU is indicated for the treatment of uncomplicated influenza caused by viruses types A and B in patients 1 year and older who have been symptomatic for no more than 2 days.

TAMIFLU is also indicated for the prophylaxis of influenza in patients 1 year and older.

Efficacy of TAMIFLU in patients who begin treatment after 48 hours of symptoms has not been established.

TAMIFLU is not a substitute for early and annual vaccination as recommended by the Centers for Disease Control's Advisory Committee on Immunization Practices (ACIP).

There is no evidence for efficacy of TAMIFLU in any illness caused by agents other than influenza viruses Types A and B.

Influenza viruses change over time. Emergence of resistance mutations could decrease drug effectiveness. Other factors (for example, changes in viral virulence) might also diminish clinical benefits of antiviral drugs. Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use TAMIFLU.

Safety Information

TAMIFLU is contraindicated in patients who have had severe allergic reactions such as anaphylaxis or serious skin reactions such as toxic epidermal necrolysis, Stevens-Johnson syndrome, or erythema multiforme to any component of TAMIFLU.

In postmarketing experience, rare cases of anaphylaxis and serious skin reactions, including toxic epidermal necrolysis, Stevens-Johnson syndrome and erythema multiforme, have been reported with TAMIFLU. Tamiflu should be stopped and appropriate treatment instituted if an allergic-like reaction occurs or is suspected.

Influenza can be associated with a variety of neurologic and behavioral symptoms, which can include events such as hallucinations, delirium and abnormal behavior, in some cases resulting in fatal outcomes. These events may occur in the setting of encephalitis or encephalopathy but can occur without obvious severe disease. There have been postmarketing reports (mostly from Japan) of delirium and abnormal behavior leading to injury, and in some cases resulting in fatal outcomes, in patients with influenza who were receiving TAMIFLU. Because these events were reported voluntarily during clinical practice, estimates of frequency cannot be made but they appear to be uncommon based on TAMIFLU usage data. These events were reported primarily among pediatric patients and often had an abrupt onset and rapid resolution. The contribution of TAMIFLU to these events has not been established. Patients with influenza should be closely monitored for signs of abnormal behavior. If neuropsychiatric symptoms occur, the risks and benefits of continuing treatment should be evaluated for each patient.

Serious bacterial infections may begin with influenza-like symptoms or may co-exist with or occur as complications during the course of influenza. TAMIFLU has not been shown to prevent such complications.

Treatment efficacy in subjects with chronic cardiac and/or respiratory disease has not been established. No difference in the incidence of complications was observed between the treatment and placebo groups in this population.

No information is available regarding treatment of influenza in patients at imminent risk of requiring hospitalization.

Efficacy of TAMIFLU has not been established in immunocompromised patients.

The concurrent use of TAMIFLU with live attenuated influenza vaccine (LAIV) intranasal has not been evaluated. However, because of the potential for interference between these products, LAIV should not be administered within 2 weeks before or 48 hours after administration of TAMIFLU, unless medically indicated.

Adverse events that occurred more frequently in patients treated with TAMIFLU than in patients taking placebo and occurred in ≥2% of patients were (TAMIFLU%, placebo%):

  • Treatment in adults – nausea (10%, 6%), vomiting (9%, 3%), bronchitis (2%, 2%)
  • Treatment in pediatrics – vomiting (15%, 9%), abdominal pain (5%, 4%), epistaxis (3%, 3%), ear disorder (2%, 1%)
  • Prophylaxis of adults – headache (18%, 18%), nausea (7%, 3%), diarrhea (3%, 2%), vomiting (2%, 1%), abdominal pain (2%, 1%)
  • Prophylaxis of pediatrics – vomiting (10%, 2%), abdominal pain (3%, 0%), nausea (4%, 1%)
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