The effective physician: seasonal influenza diagnosis and treatment.(INFECTIOUS DISEASES)

Background

Seasonal influenza is a common clinical problem that results in more 35,000 deaths and 200,000 hospitalizations annually in the United States. The Infectious Diseases Society of America recently published clinical guidelines on influenza diagnosis and management.

Conclusions

Most patients infected with seasonal influenza have either asymptomatic disease or uncomplicated febrile respiratory illness. However, severe disease leading to complications, hospitalization, and death is a risk in previously healthy persons, those with medical comorbidities, and those at both extremes of age.

Influenza vaccine is the best method of prevention of influenza, but it is not universally effective. Antiviral prophylaxis and/or treatment continue to have a significant role in influenza control.

Reverse transcriptase polymerase chain reaction (RT-PCR) is currently the most sensitive and specific test for influenza and is also useful as a confirmatory test when other screening tests (immunofluorescent antibody or direct fluorescent antibody testing or commercial point-of-care testing) for influenza is used. Viral culture is also useful as a confirmatory test. Serology is not routinely useful in direct patient care, although paired sera may be useful in research settings.

Nasopharyngeal aspirates and swabs are the preferred testing samples for most patients; however, lower respiratory samples obtained by bronchoalveolar lavage or tracheal aspirate may be useful in immunocompromised and mechanically ventilated patients.

Influenza antiviral resistance is a growing clinical problem; as such, treatment recommendations are likely to change with time.

Implementation

Influenza vaccination is recommended in all health care workers, persons aged 6 months and older who want to prevent influenza, and all nonallergic patients at increased risk for influenza complications (in accordance with annual recommendations from the Centers for Disease Control and Prevention/Advisory Committee on Immunization Practices).

A diagnosis of influenza should be considered in all patients with fever and acute respiratory signs and symptoms, or an exacerbation of chronic respiratory symptoms, occurring during influenza season. Influenza should be considered in patients who are hospitalized without fever but subsequently develop fever and respiratory illness during hospitalization. Finally, influenza should be considered in any patient with fever and acute respiratory illness who has had potential epidemiologic contact with an influenza outbreak.

Influenza testing is recommended in patients in whom the results will affect clinical decision making.

Positive screening tests outside of influenza season (or when disease activity in the community is low) and negative screening tests in times when disease activity is high may warrant confirmatory testing with RT-PCR or viral culture.

Antiviral treatment of influenza is recommended for ambulatory patients at increased risk of complications who have laboratory-confirmed (or strongly clinically suspected) influenza and are within 48 hours of the onset of illness, regardless of vaccination status.

Antiviral treatment is recommended for all patients hospitalized with influenza who are within 48 hours of the onset of illness.

Treatment with antivirals should be considered for lower-risk patients and those who have contact with persons at risk for complications who have influenza diagnosed within 48 hours of symptom onset.

There are fewer data to support treatment of patients with influenza diagnosed more than 48 hours after symptom onset.

When influenza viruses are circulating in the community antiviral prophylaxis is recommended for unvaccinated patients at high risk of influenza and/ or those who are in close contact with high-risk patients for the 2 weeks following vaccination to allow immune response to the vaccine to develop. The choice of a particular antiviral or antiviral combination should be made based on the particular strain causing disease in that patient or community.

Antiviral prophylaxis is recommended in the presence of an influenza outbreak for all institutional residents regardless of vaccination status. The prophylaxis should be continued for up to 14 days.

Antiviral chemoprophylaxis is recommended for all members of a household of a person with a high risk of influenza complications when a case of influenza occurs in one member of the household, regardless of vaccination status.

In the presence of an outbreak, antiviral chemoprophylaxis is recommended for institutional and health care employees and in high-risk patients in whom vaccine is contraindicated or not likely to be effective.

Recommendations for evaluation, vaccination, antivirals, and other issues regarding seasonal influenza may not apply to pandemic influenza. The most current recommendations for seasonal and pandemic influenza are available at www.cdc.gov/flu.

Reference

Harper S.A., et al. Seasonal influenza in adults and children--Diagnosis, treatment, chemoprophylaxis, and institutional outbreak management: Clinical practice guidelines of the Infectious Diseases Society of America. Clin. Infect. Dis. 2009;48:1003-32.

BY WILLIAM E. GOLDEN, M.D., AND ROBERT H. HOPKINS, M.D.

DR. GOLDEN (left) is professor of medicine and public health and DR. Hopkins is program director for the internal medicine/pediatrics combined residency program at the University of Arkansas, Little Rock. Write to Dr. Golden and Dr. Hopkins at our editorial offices or imnews@elsevier.com.

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