September 15, 2009
H1N1 UPDATE: For the week ending September 5, 2009, the CDC reported that influenza activity has increased in the US with “widespread disease activity” reported in 11 states. Seven of the 11 are in the southeast corner of the USA, with only Alabama spared. Closer to home, we are continuing to see sporadic activity with 36 positive tests for influenza A since September 1, 2009, out of 382 samples tested. Overall the positivity rate is still low (during epidemic disease as many as 40 percent of samples tested are positive). 97 percent of all subtyped influenza A viruses being reported are H1N1 species. To date 99.4 percent of isolates are oseltamivir susceptible.
On September 8, 2009, the CDC released revised guidelines on the use of antiviral medications in the treatment and prevention of influenza for the 2009-2010 season. These guidelines are available from the CDC flu website. Here is a quick summary of the new and significantly revised guidelines:
- All hospitalized patients with suspected or confirmed influenza (SOCI) should be treated with oseltamivir or zanamavir (if available and the patient is 7 years of age or greater).
- Treatment is recommended for persons with SOCI who are at risk for complications:
- Children younger than 5 years of age.
- Adults who are 65 years of age or older.
- Pregnant women (safety data are not available for these drugs during pregnancy, but the risk of complications warrants treatment, per the CDC).
- Persons with certain medical conditions such as asthma, renal, hepatic, hematologic (including sickle cell disease), neurologic, neuromuscular or metabolic disorders such as diabetes, immunosuppression, persons under age 19 receiving long-term aspirin therapy.
- Conversely, persons who are not at higher risk of complications (healthy older children and adults) or do not have more severe manifestations requiring hospital admission generally do not require antiviral medications for treatment or chemoprophylaxis.
- Treatment should start early if given (ideally within 48 hours of symptom onset).
- Treatment should not wait for laboratory confirmation of influenza because lab testing can delay treatment (if turnaround times are slow) and because a negative rapid test for influenza does not rule out influenza (sensitivity of rapid tests is 10 percent to 70 percent).
- The CDC also provides guidance on circumstances when clinical judgment might encourage alternative treatment strategies (see the website).
- Post-exposure prophylaxis can be considered for the following circumstances:
- Person at high-risk for complications and a close contact of someone with confirmed, probable or suspected 2009 H1N1 or seasonal influenza during that person’s infectious period (for this guidance that means one day before until 24 hours after fever ends).
- Health care personnel, public health workers and first responders who have had a recognized, unprotected close contact with a confirmed, probable or suspect case.
- Antiviral prophylaxis should not be used for post-exposure chemoprophylaxis in healthy children or adults for community, school, camp or other settings.
- Chemoprophylaxis is not recommended if more than 48 hours have elapsed since the last contact with the infectious person or if the exposure occurs outside the infectious period.
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