Influenza Disease Summary

Last updated: 07 March 2025

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Overview

Influenza has a wide clinical spectrum, and these are discussed in the Introduction section.

According to the World Health Organization (WHO) seasonal influenza spreads rapidly and occurs mainly during winter in temperate areas and irregularly throughout the year in tropical areas. A detailed discussion about confirmed cases and prevalence of influenza locally and regionally is featured in the Epidemiology section.

There are different types of influenza infection, mainly seasonal and avian influenza. Each of these types are in the Etiology section.

The Pathophysiology section discusses the development and effects of influenza virus to the patient once infected. 

History and Physical Examination

Patients with influenza infection typically presents with fever and cough. Other signs and symptoms of seasonal and avian influenza are enumerated in the Clinical Presentation section.


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Diagnosis

Laboratory tests such as rapid viral tests and reverse transcriptase-polymerase chain reaction may be done to confirm the diagnosis of seasonal and avian influenza. These tests and indications for their use are discussed in detail in the Laboratory Tests and Ancillaries section.

Other diseases caused by viral infections should be ruled out to diagnose influenza and these are enumerated in the Differential Diagnosis section.

Management

The initial management of influenza in adults is based on clinical presentation and epidemiological data. Initial management decisions based on whether disease is caused by seasonal or avian influenza are discussed in the Principles of Therapy section.

Symptomatic therapy options and antivirals that can be used in managing seasonal and avian influenza are discussed in detail in the Pharmacological Therapy section.

Several non-drug options to consider that may aid in the management of patients with influenza are featured in the Nonpharmacological section. Supportive therapy for hospitalized patients (eg oxygen therapy, hydration, nutrition) is also in this section.

Recommendations for the administration of vaccines to prevent influenza are enumerated and is further elaborated in the Prevention section. Infection control or isolation procedures are also in this section.

Factors to consider in monitoring outpatients and inpatients with influenza are in the Monitoring section.

Possible Complications are discussed in brief in this section.