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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.

Review Sample Diagnostic Profiles and Treatment Decisions

Sharpen your diagnostic skills by reviewing profiles of a variety of patients presenting with flu symptoms:

• Adult Profile for Influenza Treatment Adobe PDF format
• Adult Profile for Influenza Prevention Adobe PDF format
• Pediatric Profile for Influenza Treatment Adobe PDF format
• Pediatric Profile for Influenza Prevention Adobe PDF format
• Get the free Adobe^® Reader^®

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