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Antiviral guidance for H1N1 influenza

June 17, 2009

The CDC says it's important to get the word out to clinicians to emphasize early, empiric antiviral treatment for hospitalized patients and high-risk outpatients with suspected, probable, or confirmed novel swine-origin influenza A (H1N1) virus infection. This message is particularly important for those in primary care (including internists, pediatricians, family practitioners, and OB-GYN physicians) and hospital-based clinicians (emergency physicians, hospitalists, and intensivists).

Preliminary information indicates that some hospitalized patients with novel influenza A (H1N1) virus infection have not been treated with antivirals or that treatment with antiviral agents was delayed until confirmatory testing was completed. In particular, some patients with chest x-ray evidence of pneumonia and influenza symptoms have not received antivirals early. While data from seasonal influenza indicates that early antiviral treatment is most effective (within 48 hours of symptom onset), some studies have reported a benefit in treating hospitalized patients. Therefore, initiating therapy at the earliest possible time is desirable, including at hospital admission, if patients were not previously treated.

Clinicians should be aware that influenza virus infection can cause primary viral pneumonia and early treatment of people with influenza-related pneumonia is desirable. Additionally, empiric treatment with influenza antiviral medications does not preclude empiric treatment for bacterial co-infections. Specific influenza testing should be performed for any hospitalized patient with suspected novel influenza A (H1N1) virus infection.

The CDC Antiviral recommendations are available at: http://www.cdc.gov/h1n1flu/recommendations.htm. The CDC Testing recommendations are available at: http://www.cdc.gov/h1n1flu/specimencollection.htm.

Accordingly, the CDC would like to emphasize antiviral treatment for the following:

1. All hospitalized patients with suspected, probable, or confirmed novel influenza A (H1N1) virus infection should be empirically treated with oseltamivir or zanamivir as early after illness onset as possible.
   
   No comparative studies have been done to assess whether higher doses or longer treatment courses might be more effective for severely ill patients. However, a longer duration of treatment should be considered for severe illness that persists at the end of the usual 5 day course. Some experts also recommend higher treatment doses (e.g., 150 mg oseltamivir twice per day), based on concerns about the potential for lower oseltamivir absorption, higher viral loads, and reduced delivery of oseltamivir to damaged tissue among severely ill patients. Patients who have received higher treatment doses or longer treatment durations have tolerated these regimens without substantial increase in adverse events, based on limited data.
   
   
2. All outpatients with suspected novel influenza A (H1N1) virus infection who are at higher risk for influenza complications should be empirically treated with oseltamivir or zanamivir as early after illness onset as possible.
   
   
3. Groups with a higher risk for influenza complications:
   1. Children younger than 5 years old. The risk for severe complications from seasonal influenza is highest among children younger than 2 years old.
   2. Adults 65 years of age and older.
   3. Persons with the following conditions:
      1. Chronic pulmonary (including asthma), cardiovascular (except hypertension), renal, hepatic, hematological (including sickle cell disease), neurologic, neuromuscular, or metabolic disorders (including diabetes mellitus);
      2. Immunosuppression, including that caused by medications or by HIV;
      3. Pregnant women;
      4. Persons younger than 19 years of age who are receiving long-term aspirin therapy;
      5. Residents of nursing homes and other chronic-care facilities.

WHO moves H1N1 to pandemic alert level phase 6
The WHO has moved to pandemic alert level 6, but this is not changing the present response in the United States or in Iowa. This increase in the WHO pandemic phase designation is based on geographic spread of the influenza virus, not on the severity of the illness.

The Iowa Department of Public Health says there may be continuing transmission of both our seasonal flu strains and novel influenza A (H1N1) over the summer. Thus, it continues to be important for Iowans to remember personal health actions:

• Cover coughs and sneezes with a tissue or your elbow.
• Stay home from work or school and do not travel while ill.
• Wash your hands often.

Iowa is working to be prepared for what happens in the fall if H1N1 returns when the traditional flu season starts. Meanwhile, influenza surveillance will continue throughout the summer.

The Iowa Department of Public Health says that all novel influenza A (H1N1) data will be combined with the regular seasonal flu data. A weekly report will continue to be published on the Iowa Influenza Surveillance Network (IISN) Web site at www.idph.state.ia.us/adper/iisn.asp. For more information, visit http://www.idph.state.ia.us/h1n1/ or go to www.cdc.gov/swineflu/ or visit the AMA's Swine Flu site which features up-to-date clinical guidance, treatment information, resources and news about H1N1.