The Diagnosis of Influenza | Tamiflu� (oseltamivir phosphate)

Influenza Management

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.²

Difficulties of diagnosing children

Influenza is responsible for substantial morbidity in children and increases the need for healthcare, including hospitalization.⁸

A prospective, population-based study showed that:

83% of children were misdiagnosed in the outpatient setting.⁹
72% of children were misdiagnosed in the inpatient setting.⁹

Flu vaccine effectiveness varies. Therefore, influenza should not be ruled out in the differential diagnosis.¹⁸

Early diagnosis of influenza can reduce the inappropriate use of antibiotics and provide the option of using antiviral therapy such as Tamiflu.^{10, 21}

Patients who may benefit from Tamiflu³²

The CDC recommends initiation of antiviral treatment as early as possible (within the first 2 days of symptom onset) for any patient who:

Is at higher risk of influenza complications, including children <2 years of age.
Is not at high risk but presents with confirmed or suspected influenza.

Antiviral therapies such as Tamiflu may:

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

Encourage swift action for patients who may benefit from Tamiflu. To be effective at treating and reducing the duration of influenza symptoms, Tamiflu treatment should be initiated within 48 hours of the onset of flu symptoms.¹

Indication

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.

Resources to help improve your influenza diagnoses

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

Use the FluTracker to find out where the flu is circulating nationwide.

Proper Diagnosis Is Essential for Early and Appropriate Influenza Treatment¹⁷

flu diagnosis chart

Early and accurate diagnosis of influenza helps guide treatment and prevention decisions.

Next Step: Learn about management of influenza ›

Did you know?

The CDC recommends antivirals in addition to yearly vaccination and preventive measures as part of an effective influenza management plan.^{30, 31}

Learn more ›

Indications and Limitations of Use

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 vaccination as recommended by the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices.
There is no evidence for efficacy of TAMIFLU in any illness caused by agents other than influenza virus types A and B.
Influenza viruses change over time. Emergence of resistant mutations could decrease drug effectiveness. Other factors (for example, changes in viral virulence) might also diminish clinical benefit of antiviral drugs. Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use TAMIFLU.

Important Safety Information

Severe allergic 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.

Neurologic symptoms

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. 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 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 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.
Safety and efficacy of TAMIFLU for treatment of influenza in pediatric patients less than 2 weeks of age have not been established.
Safety and efficacy of TAMIFLU for prophylaxis of influenza have not been established for pediatric patients less than 1 year of age.

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

The safety profile observed in pediatric patients 2 weeks to less than 1 year of age was consistent with the established safety profile of pediatric subjects aged 1 year and above, with vomiting, diarrhea, and diaper rash being the most frequently reported adverse reactions.
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%).
- Treatment in pediatrics — vomiting (15%, 9%), abdominal pain (5%, 4%), ear disorder (2%, 1%).
- Prophylaxis of adults — 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%).

Please see the TAMIFLU full Prescribing Information for complete safety information.

Diagnosis of Influenza