Background: Avian influenza (H5N1) or “bird flu” is still around, despite waning media attention. H5N1 causes more severe symptoms than other type A influenza strains. Clinical features include persistent fever, cough, lymphopenia, and progressive respiratory difficulty over three to five days. Respiratory failure develops in most cases, with an estimated mortality of 50 percent. To date, most patients have reported exposure to sick and dying poultry in regions with known H5N1 infection, but there has been limited human-to-human transmission. There is serious risk of a global pandemic if H5N1 becomes easily transmissible between humans, and family physicians could be heavily involved in the diagnosis and management of any such pandemic. The Infectious Diseases Society of America and American Thoracic Society have released joint consensus guidelines addressing the management of potential avian influenza cases.
Recommendations: Patients with influenza-like symptoms and with known exposure to poultry in H5N1-susceptible areas should be tested for H5N1 infection. Pharyngeal swabs sent for reverse-transcriptase polymerase chain reaction testing is currently the most sensitive method for confirming H5N1 infection. Other methods include nasopharyngeal swabs and other body fluid and stool testing. Convalescent-phase antibody testing can be performed, but it is not widely available. Rapid bedside tests for influenza A have been successfully used as screening tools, but they cannot distinguish between H5N1 and less severe strains.
If avian influenza is suspected, droplet precautions, respiratory isolation, and standard infection control measures should be initiated until H5N1 infection can be ruled out. Health care workers should use N-95 or higher respirators during any clinical situation in which respiratory aerosol particles could be present.
Empiric treatment of suspected H5N1-infected patients should begin immediately with the neuraminidase inhibitor oseltamivir (Tamiflu), because recently isolated H5N1 strains have been resistant to the older agents amantadine (Symmetrel) and rimantadine (Flumadine). Current adult dosing remains the same for suspected avian influenza as for “regular” influenza (i.e., 75 mg twice daily for five days). Antibiotic therapy should also be initiated to prevent development of secondary bacterial pneumonia, including Streptococcus pneumoniae and Staphylococcus aureus, which are the most common. Appropriate agents include cefotaxime (Claforan), ceftriaxone (Rocephin), or fluoroquinolones. Treatments against methicillin-resistantS. aureus (e.g., vancomycin or linezolid [Zyvox]) should be avoided, except in cases of confirmed infection or a compatible clinical situation such as shock and necrotizing pneumonia.
Conclusion: An avian influenza pandemic can stress all aspects of the health care system, and primary care physicians will play a critical role in the early detection, management, and containment of any outbreak. Maintaining a high clinical index of suspicion, especially for influenza with severe respiratory sequelae, will be crucial. Should a pandemic occur, recommendations will likely evolve as the situation progresses. Web sites for the Centers for Disease Control and Prevention (http://www.cdc.gov) and the World Health Organization (http://who.int) will be useful references in this event. Regularly updated information can also be found athttp://www.pandemicflu.gov, a Web site sponsored by the U.S. Department of Health and Human Services.