CDC Releases Updated Guidance for Testing of Persons with Suspected Infection with Avian Influenza in the United States
By Eric Toner, M.D., June 8, 2006
Yesterday, June 7, the CDC released new guidelines for the testing of patients with possible H5N1 infection in the U.S. A summary follows. Clinicians should consult the full document for complete details.
Reporting and Testing Guidelines
In brief, testing for H5N1 infection is recommended for a patient with:
documented fever ≥38°C
radiographically confirmed pneumonia for which an alternate diagnosis has not been established
travel within the past 10 days to a country with documented H5N1 infections in humans or birds
at least one of the following potential exposures during travel
> direct contact with sick or dead domestic poultry
> direct contact with surfaces contaminated with poultry feces
> consumption of raw or incompletely cooked poultry or poultry products
> direct contact with sick or dead wild birds suspected or confirmed to have influenza H5N1
> close contact (within 1 meter) of a person who was hospitalized or died due to a severe unexplained respiratory illness.
In addition, anyone with the above symptoms who had close contact, within 3 feet, with an ill person with confirmed or suspected H5N1 or who has worked with live H5N1 virus in a laboratory would be an appropriate candidate for testing.
Patients with mild or atypical symptoms but with the above exposure histories can be considered for testing on a case-by-case basis in consultation with local and state health departments.
Lastly, a patient with severe respiratory disease whose epidemiological information is uncertain or otherwise suspicious, but who does not meet the criteria above, may be considered on a case by case basis.
Clinicians should contact their local or state health department immediately to report any suspected human case of H5N1 in the United States.
Specimen Collection and Testing Guidelines
Oropharyngeal swab specimens and lower respiratory tract specimens are preferred over nasal or nasopharyngeal swab specimens because they appear to contain the highest quantity of H5N1 virus.
Testing is more sensitive if collected within the first 3 days of illness and if serial specimens are obtained over several days.
H5N1-specific RT-PCR testing conducted under Biosafety Level 2 conditions is the preferred method for diagnosis. According to the CDC, all state public health laboratories, several local public health laboratories, and CDC are able to perform H5N1 RT-PCR testing, and are the recommended sites for initial diagnosis.