Diagnosis of Influenza

Diagnosing Influenza Can Be a Challenge

It is very difficult to distinguish influenza from viral and bacterial causes of respiratory illness on the basis of symptoms alone.1

Difficulties of diagnosing children

Influenza is responsible for substantial morbidity in children and increases the need for healthcare, including hospitalization.2

A prospective, population-based study showed that3:

  • 83% of children of < 5 years of age were misdiagnosed in the outpatient setting.
  • 72% of children of < 5 years of age were misdiagnosed in the inpatient setting.

Flu vaccine effectiveness can be based on multiple factors, including similarity to the circulating influenza strain(s) and the health status of the vaccine recipient. Therefore, influenza should not be ruled out in the differential diagnosis.4

Early diagnosis of influenza can reduce the inappropriate use of antibiotics and provide the option of using antiviral therapy.5,6

Patients who may benefit from antiviral therapy7

The CDC recommends initiation of antiviral treatment as early as possible (within the first 2 days of symptom onset) for certain patient groups. These may include, but are not limited to:

  • Patients at higher risk of influenza complications, including children < 2 years of age.
  • Patients with chronic, complicated, or progressive illness.
  • Adults aged 65 years and older.

Antiviral treatment can also be considered for any previously healthy, symptomatic outpatient not at high risk with confirmed or suspected influenza on the basis of clinical judgment, if treatment can be initiated within 48 hours of symptom onset.

Antiviral therapies may:

  • Reduce the severity of illness.
  • Shorten the duration of illness.

Encourage swift action for patients who may benefit from antiviral therapy. To be effective at treating and reducing the duration of influenza symptoms, treatment should be initiated within 48 hours of the onset of flu symptoms.

Resources to help inform your influenza diagnoses

Influenza surveillance by state and local health departments and CDC can provide information regarding the presence of influenza viruses in the community.

Use the Flu Tracker to find out where the flu is circulating nationwide.

Proper Diagnosis Is Essential for Early and Appropriate Influenza Treatment8


References

  1. Centers for Disease Control and Prevention. Seasonal Influenza Q&A. http://www.cdc.gov/flu/about/qa/disease.htm. Updated September 18, 2015. Accessed October 1, 2015.
  2. Whitley RJ, Hayden FG, Reisinger KS, et al. Oral oseltamivir treatment of influenza in children. Pediatr Infect Dis J. 2001;20:127-133.
  3. Poehling KA, Edwards KM, Weinberg GA, et al; New Vaccine Surveillance Network. The underrecognized burden of influenza in young children. N Engl J Med. 2006;355:31-40.
  4. Atkinson W, Wolfe C, Hamborsky J, eds. Epidemiology and Prevention of Vaccine-Preventable Diseases. 12th ed., second printing. Washington, DC: Public Health Foundation; 2012. http://www.cdc.gov/vaccines/pubs/pinkbook/index.html. Updated July 25, 2014. Accessed October 2, 2014.
  5. Centers for Disease Control and Prevention. Influenza Symptoms and the Role of Laboratory Diagnostics. http://www.cdc.gov/flu/professionals/diagnosis/labrolesprocedures.htm. Updated October 16, 2014. Accessed October 1, 2015.
  6. Centers for Disease Control and Prevention. Rapid Diagnostic Testing for Influenza: Information for Health Care Professionals. http://www.cdc.gov/flu/professionals/diagnosis/rapidclin.htm. Updated February 18, 2015. Accessed October 1, 2015.
  7. Centers for Disease Control and Prevention. Influenza Antiviral Medications: Summary for Clinicians. http://www.cdc.gov/flu/professionals/antivirals/summary-clinicians.htm. Updated February 25, 2015. Accessed October 1, 2015.
  8. National Institute of Allergy and Infectious Diseases. Is It a Cold or the Flu? https://www.niaid.nih.gov/topics/Flu/Documents/sick.pdf. Updated August 2014. Accessed December 21, 2015.

Indications

Tamiflu is indicated for the treatment of acute, uncomplicated illness due to influenza infection in patients 2 weeks of age 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 influenza vaccination
  • 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. Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use Tamiflu

Important Safety Information

Serious Skin/Hypersensitivity Reactions

  • 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, and erythema multiforme to any component of Tamiflu
  • In postmarketing experience, 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

Neuropsychiatric Events

  • 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
  • Closely monitor patients with influenza for signs of abnormal behavior. If neuropsychiatric symptoms occur, evaluate the risks and benefits of continuing treatment for each patient

Bacterial Infections

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

Limitations of Populations Studied

  • Efficacy of Tamiflu in the treatment of influenza in patients with chronic cardiac disease and/or respiratory disease has not been established. No information is available regarding treatment of influenza in patients with any medical condition sufficiently severe or unstable to be considered at imminent risk of requiring hospitalization
  • Efficacy of Tamiflu for treatment or prophylaxis of influenza has not been established in immunocompromised patients

Concurrent Use with Live Attenuated Influenza Vaccine

  • 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

Most Common Adverse Reactions

  • Adverse events that occurred more frequently in patients treated with Tamiflu than in patients taking placebo (frequency ≥ 2%) across clinical trials were nausea, vomiting, abdominal pain, ear disorder, and diarrhea
  • The safety profile observed in pediatric patients 2 weeks to less than 1 year of age was consistent with the established safety profile of subjects aged 1 year and above, with vomiting, diarrhea and diaper rash being the most frequently reported adverse reactions

For additional important safety information, please see Tamiflu full prescribing information at www.tamiflu.com.

You are encouraged to report side effects to Genentech by calling 1-888-835-2555 or to the FDA by visiting www.fda.gov/medwatch or calling 1-800-FDA-1088.

Indications and Important Safety Information

Indications

Tamiflu is indicated for the treatment of acute, uncomplicated illness due to influenza infection in patients 2 weeks of age 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 influenza vaccination
  • 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. Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use Tamiflu

Important Safety Information

Serious Skin/Hypersensitivity Reactions

  • 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, and erythema multiforme to any component of Tamiflu
  • In postmarketing experience, 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

Neuropsychiatric Events

  • 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
  • Closely monitor patients with influenza for signs of abnormal behavior. If neuropsychiatric symptoms occur, evaluate the risks and benefits of continuing treatment for each patient

Bacterial Infections

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

Limitations of Populations Studied

  • Efficacy of Tamiflu in the treatment of influenza in patients with chronic cardiac disease and/or respiratory disease has not been established. No information is available regarding treatment of influenza in patients with any medical condition sufficiently severe or unstable to be considered at imminent risk of requiring hospitalization
  • Efficacy of Tamiflu for treatment or prophylaxis of influenza has not been established in immunocompromised patients

Concurrent Use with Live Attenuated Influenza Vaccine

  • 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

Most Common Adverse Reactions

  • Adverse events that occurred more frequently in patients treated with Tamiflu than in patients taking placebo (frequency ≥ 2%) across clinical trials were nausea, vomiting, abdominal pain, ear disorder, and diarrhea
  • The safety profile observed in pediatric patients 2 weeks to less than 1 year of age was consistent with the established safety profile of subjects aged 1 year and above, with vomiting, diarrhea and diaper rash being the most frequently reported adverse reactions

For additional important safety information, please see Tamiflu full prescribing information at www.tamiflu.com.

You are encouraged to report side effects to Genentech by calling 1-888-835-2555 or to the FDA by visiting www.fda.gov/medwatch or calling 1-800-FDA-1088.

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