Interim Recommendations for U.S. Surveillance and Diagnostic Evaluation
The Centers for Disease Control and Prevention (CDC) recommends that state and local health departments, hospitals, and clinicians enhance their efforts to identify patients who could be infected by influenza A (H5N1) virus and take infection-control precautions when influenza A (H5N1) is suspected.
Interim Recommended Infection-Control Precautions* for Influenza A (H5N1)
- All patients with a febrile respiratory illness should be asked about their recent travel history and managed using Respiratory Hygiene/Cough Etiquette in HealthCare Settings guidelines.
- Isolation precautions for all hospitalized patients who have or are under evaluation for influenza A (H5N1) are the same as those that should be used for severe acute respiratory syndrome (SARS), as follows:
- Pay careful attention to hand hygiene before and after all patient contact.
- Use gloves and gown for all patient contact.
- Wear eye protection when within 3 feet of the patient.
- Place the patient in an airborne isolation room (i.e., monitored negative air pressure in relation to surrounding areas with 6 to 12 air changes per hour).
- When entering the patient’s room, use a fit-tested respirator at least as protective as an N95 filtering-facepiece respirator approved by the National Institute for Occupational Safety and Health.
- Outpatients or hospitalized patients discharged in <14 days should be isolated in the home setting on the basis of principles for home isolation of SARS patients (see guidance available at the CDC Web site.
- These precautions should be continued for 14 days after onset of symptoms until an alternative diagnosis is established or diagnostic test results indicate that the patient is not infected with influenza A virus.
*Note: Additional information about health-care isolation precautions is available at the CDC Web site.
Testing of hospitalized patients for influenza A (H5N1) infection is indicated when both of the following exist: 1) radiographically confirmed pneumonia, acute respiratory distress syndrome (ARDS), or other severe respiratory illness for which an alternative diagnosis has not been established and 2) a history of travel within 10 days of symptom onset to a country with documented H5N1 avian influenza infections in poultry or humans. Ongoing listings of countries affected by avian influenza are available from the World Organization for Animal Health. Available at http://www.oie.int/eng/en_index.htm
Testing for influenza A (H5N1) also should be considered on a case-by-case basis in consultation with state and local health departments for hospitalized or ambulatory patients with all of the following: 1) documented temperature of >100.4ºF (>38ºC); 2) cough, sore throat, or shortness of breath; and 3) history of contact with poultry or domestic birds (e.g., visited a poultry farm, a household raising poultry, or a bird market) or a known or suspected patient with influenza A (H5N1) in an H5N1-affected country within 10 days of symptom onset.
Recommended Laboratory Testing Procedures
The highly pathogenic avian influenza A (H5N1) virus requires Biosafety Level (BSL)-3+ laboratory conditions for certain procedures. CDC recommends that virus isolation studies on respiratory specimens from patients who meet the testing criteria should not be performed unless all BSL-3+ conditions are met. However, clinical specimens can be tested by polymerase chain reaction (PCR) assays by using standard BSL-2 work practices in a Class II biological safety cabinet. CDC has developed real-time PCR protocols** for various respiratory pathogens, including severe acute respiratory syndrome (SARS) and influenza A and B viruses. In addition, commercially available antigen-detection tests can be used under BSL-2 levels to test for influenza. Although these rapid tests for human influenza also can detect avian influenza A (H5N1) viruses, the sensitivity of these tests is substantially lower than that of virus culture or PCR.
Specimens from persons meeting clinical and epidemiologic indications for testing should be sent to CDC if they test positive for influenza A either by PCR or antigen detection testing, or if PCR assays for influenza are not available locally. CDC also will accept, for follow-up testing, specimens from persons meeting the clinical and epidemiologic indications but testing negative on the rapid tests when PCR assay was not available. Requests for testing by CDC should come through local and state health departments, which should contact CDC’s Emergency Operations Center, telephone 770-488-7100.
**Note: These protocols are available to public health laboratories and have been posted, under SARS (password required), by the Association of Public Health Laboratories at http://www.aphl.org/members_only/index.cfm.
