H1N1 Update for Hospital-Based Physicians
Can you relay the latest information regarding swine flu?
K. Thane, MD, Lincoln, Neb.
Dr. Hospitalist responds: Dr. Thane, please do not feel alone. The information regarding 2009 novel H1N1 influenza (swine flu) has been coming out quickly, and the recommendations have been evolving over time. I commend you for your efforts to keep up with the information. All of us have an important role in this pandemic.
I suspect that some of the information I am providing might have changed by the time this article is published. The best advice I can give you is to frequently check the H1N1 flu section of the Centers for Disease Control and Prevention Web site (www.cdc.gov). The CDC’s “FluView” is particularly helpful. It is a weekly “surveillance report” prepared by the CDC’s influenza division. It offers activity estimates reported by “state and territorial epidemiologists.”
Here is a list of what I consider to be the most interesting facts and recommendations regarding the H1N1 pandemic:
5. Fever (93%) and cough (83%) are the most common symptoms of hospitalized patients with the novel H1N1 influenza. Less-frequent symptoms include shortness of breath (54%) and fatigue (40%).
4. Preliminary observation suggests that obesity may be a risk factor for hospitalization and death. A body mass index (BMI) greater than or equal to 40 appears to increase risk of hospitalization and death. Patients with a BMI of 30 to 39 might also be at increased risk.
3. The CDC recommends testing for all patients hospitalized with suspected H1N1 influenza. There are a number of diagnostic tests commercially available to detect the presence of influenza virus in respiratory specimens: cell culture, direct antigen tests, and detection of influenza RNA by reverse transcriptase polymerase chain reaction (rT-PCR). The rT-PCR is the most sensitive and specific test. The test takes about four to six hours and differentiates between influenza types and subtypes.
The rapid influenza detection tests are direct antigen tests that detect influenza viral nucleoproteins. These tests offer the advantage of producing results within 30 minutes, but the sensitivity is lower than viral culture or rT-PCR. Several commercially available rapid antigen tests can differentiate between influenza A and B, but none can differentiate influenza subtypes.
2. All patients at high risk for complications from known or suspected H1N1 influenza should be treated with antiviral medications. Treatment should start as soon as possible, even before laboratory confirmation of infection. High-risk groups include patients 5 years and younger or 65 years and older, pregnant women, those with chronic medical or immunosuppressive conditions, and patients 19 years or younger on chronic aspirin therapy. All patients hospitalized with the novel H1N1 influenza should be treated with antiviral medications regardless of time of symptom onset.
Oseltamivir (Tamiflue) or zanamivir (Relenza) are recommended for treatment. Oseltamivir is administered by mouth, 75 mg twice daily for five days. Zanamivir is orally inhaled, 10 mg every 12 hours for five days. Oseltamivir resistance does not predict Zanamivir resistance.
1. Chemoprophylaxis is recommended for individuals at high risk for complications who were in close contact with an individual with known or suspected H1N1 influenza. It is not necessary in healthy children and adults, and it is not recommended more than 48 hours after exposure. Sitting across a table from a symptomatic patient would not be considered close contact. TH