Influenza infection

Last reviewed: 23 Apr 2022
Last updated: 10 May 2022

Summary

Definition

History and exam

Key diagnostic factors

  • winter season
  • current influenza outbreak
  • unvaccinated
  • fever with cough
More key diagnostic factors

Other diagnostic factors

  • sore throat
  • cervical lymphadenopathy
  • dyspnea
Other diagnostic factors

Risk factors

  • age ≥65 years
  • age 6-59 months
  • chronic cardiovascular or respiratory conditions
  • diabetes
  • hemoglobinopathy
  • immunocompromise
  • chronic kidney disease (CKD)
  • pregnancy
  • caregivers and household contacts of high-risk groups
  • healthcare workers
More risk factors

Diagnostic investigations

1st investigations to order

  • clinical diagnosis
More 1st investigations to order

Investigations to consider

  • viral culture
  • direct immunofluorescent antibody staining
  • reverse transcriptase-polymerase chain reaction
  • serology
  • enzyme immunoassay (EIA)
  • rapid diagnostic tests
  • chest x-ray
More investigations to consider

Treatment algorithm

INITIAL

exposure to infected individual(s) in at-risk population

ACUTE

adults

children

Contributors

Authors

Cristine Radojicic, MD

Staff Physician

Department of Pulmonary, Allergy and Critical Care

Cleveland Clinic

Cleveland

OH

Disclosures

CR declares that she is on Advisory boards for CSL Behring and Speakers Bureau Biocryst.

Peer reviewers

Waleed Javaid, MD, FACP, FIDSA

Associate Professor

Medical Director of Infection Control

Infectious Disease

Department of Medicine

SUNY Upstate Medical University

Syracuse

NY

Disclosures

WJ declares that he has no competing interests.

Rachel L. Miller, MD, FAAAAI

Associate Professor of Clinical Medicine and Environmental Health Sciences

Columbia University College of Physicians and Surgeons

New York

NY

Disclosures

RLM declares that she has no competing interests.

Mark Sands, MD, FAAAAI

Chief

SUNY Buffalo School of Medicine

Division Allergy and Immunology

Buffalo

NY

Disclosures

MS declares that he has no competing interests.

An De Sutter, MD, PhD

Associate Professor

Department of General Practice and Primary Health Care

Ghent University

Ghent

Belgium

Disclosures

ADS declares that she has no competing interests.

  • Differentials

    • Coronavirus disease 2019 (COVID-19)
    • Bacterial pneumonia
    • Respiratory syncytial virus (RSV) infection
    More Differentials
  • Guidelines

    • Recommended adult immunization schedule for ages 19 years or older, United States, 2022
    • Recommended child and adolescent immunization schedule for ages 18 years or younger, United States, 2022
    More Guidelines
  • Patient leaflets

    Flu

    Antibiotics: what you need to know

    More Patient leaflets
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