Influenza is in the news again. As far as VEP sites are concerned, the CDC reports widespread influenza activity in California and Texas, with less activity in New Mexico and Tennessee. This pattern is corroborated by many of our ED Medical Directors. Some of the information below is from the CDC website: http://www.cdc.gov/flu/professionals/index.htm
The predominant virus this year is the Influenza A (H1N1) strain which caused a pandemic in 2009. Only a very tiny percentage of the 2009 H1N1 viruses have shown resistance to oseltamivir (Tamiflu), so resistance is not relevant to ED treatment decisions.
Period of contagion:
The incubation period for influenza is 1-4 days with an average of 2 days. Patients are contagious from the day before illness onset until about a week later. Virus shedding and contagion are greatest during the first 2-3 days of illness.
- If the results are not likely to change your management, you probably shouldn’t do the test.
- Most patients with influenza symptoms do not need testing and can be treated empirically with antivirals.
- Some of the rapid influenza tests can give false negatives, so do not withhold treatment solely because of a negative test result.
General comments regarding treatment:
- Influenza antivirals may only modestly reduce symptom severity and duration, but they may significantly reduce the risk of complications.
- Antivirals are most likely to be efficacious if taken within the first 48 hours of symptom onset.
- Antiviral treatment generally should not await laboratory confirmation of influenza.
- Influenza vaccination does not rule out the possibility of influenza infection.
Who to treat:
- Kaiser Permanente’s Infectious Diseases Committee recommends antivirals for abrupt onset of fever with cough and/or myalgias when there is no other obvious etiology.
- Antiviral treatment can be considered for any symptomatic outpatient who is not at high risk, with confirmed or suspected influenza, if treatment can be initiated within 48 hours of illness onset.
- Patients requiring admission with respiratory infections or influenza symptoms should be treated.
- The following high risk patients with influenza symptoms should be treated:
- Over 65 or under 2 years of age.
- Chronic medical conditions: cardiac, pulmonary (including asthma), renal, hepatic, hematologic, neurologic, metabolic (including diabetes mellitus).
- Pregnant or up to 2 weeks post-partum.
- Morbidly obese.
- Younger than 19 years on long-term aspirin therapy.
- Residents of nursing homes and other chronic-care facilities.
- American Indians and Alaska Natives.
Please feel free to contact me if you have any questions about influenza.
Robert Wyman, MD | Vice President of Quality
Valley Emergency Physicians Medical Group, Inc.
Hospitalist Services Medical Group