Prevention

The most effective way to reduce morbidity and mortality from influenza is through vaccination. Efficacy rates for vaccination range from 70% to 90% when a good match is made between circulating virus and vaccine antigen.¹ The CDC's Advisory Committee on Immunization Practices recommends immunization of all people 6 months and older for the 2011-2012 flu season.²

Diagnosis and Clinical Course

The symptoms of influenza and other infections of the respiratory tract can be similar (see table). Until influenza is widespread in the community, the diagnosis can be difficult to make with certainty. Focus on symptom onset and severity.³

When diagnosis is in doubt and community prevalence is low, look to rapid diagnostic tests, which have sensitivity rates of 70% and specificity rates of 90%.³ Because false negatives may occur, don't delay treatment if you suspect influenza in someone who is in a high-risk group.

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When an exact diagnosis is necessary, request definitive diagnostic tests (real-time reverse transcriptase polymerase chain reaction, viral culture) rather than rapid tests.

Uncomplicated influenza typically resolves in 3 to 7 days, but malaise and fatigue can persist for more than 2 weeks. In older adults, young children, patients with other comorbid conditions and pregnant women, the disease can have severe complications.

Complications of Influenza

Potential complications of influenza include pneumonia, otitis media, sinusitis, encephalitis, myositis and tracheobronchitis. Pneumonia is the most prevalent complication. Whenever possible, ensure that all patients who meet criteria receive pneumococcal vaccination at the same time as influenza vaccination.

Treatment

Influenza is a viral illness. In the otherwise healthy adult or older child, only supportive care is needed. Treatment with antivirals can decrease the severity of symptoms and shorten the course of the illness, but these results are only achievable if pharmacotherapy begins within 48 hours of symptom onset. Early empiric treatment is preferable to prophylaxis, to avoid resistance.⁴ In general, patients who are not hospitalized or in a high-risk category are not considered candidates for antiviral treatment. However, clinical judgment should always prevail.⁵

Priority groups for treatment with antiviral medications are hospitalized patients with confirmed or suspected influenza, patients in high-risk categories with confirmed or suspected influenza, and patients with signs and symptoms of lower respiratory illness.

Resistance and circulating viruses change from season to season, so check the CDC website for relevant information about this year's influenza activity.⁵ All antivirals are considered category C. Antiviral treatment in pregnant women was endorsed by the CDC as a best practice during the H1N1 outbreak in 2009.

Final Notes

The best treatment for influenza is vaccination against the disease and its most common complication, pneumonia. During outbreaks, respiratory hygiene and good hand washing are paramount in preventing disease spread. ■

References

1. Glezen WP. Clinical practice. Prevention and treatment of seasonal influenza. N Engl J Med. 2008;359(24):2579-2585.

2. Centers for Disease Control and Prevention. Seasonal influenza. 2011-12 influenza vaccine and vaccination information. http://www.cdc.gov/flu/flu_vaccine_updates.htm. Accessed Sept. 30, 2011.

3. Montalto NJ. An office-based approach to influenza: clinical diagnosis and laboratory testing. Am Fam Physician. 2003;67(1):111-118.

4. Matin M, Goldschmidt RH. Influenza management guide 2009-2010. Am Fam Physician. 2009;80(11):1220.

5. Centers for Disease Control and Prevention. Seasonal influenza. Information for health professionals. http://www.cdc.gov/flu/professionals. Accessed Sept. 30, 2011.

Debra Schuerman is a family nurse practitioner who is a market educator for Take Care Health Services in the St. Louis and Peoria, Ill., markets.