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Clinicians should be aware of the possibility of influenza A(H5N1) bird flu in humans with exposure to poultry after a tested positive for the highly pathogenic strain, .

The A(H5N1) strain should be considered among those who have had contact with potentially infected birds, contact with infected water or surfaces contaminated with bird feces or bird parts, and those with prolonged contact with infected birds in a confined space.

Epidemiological criteria also include those who were exposed to an infected person (less than 6 feet apart) and laboratory-related exposure.

Exposed patients may be treated with the antivirals oseltamivir (Tamiflu) or zanamivir (Relenza) at one dose twice daily. Exposed close contacts may be given oseltamivir. However, the agency noted that this is not generally recommended for patients who used appropriate personal protective equipment (PPE) while handling infected birds or in "decontaminating infected environments." For patients wearing appropriate PPE, they should be monitored for symptoms "beginning after their first exposure and for 10 days after their last exposure," the CDC said.

If a patient becomes symptomatic, they should be treated with oseltamivir, zanamivir, or baloxavir (Xofluza) within 48 hours of exposure, and hospitalized individuals should receive oral or enteral oseltamivir.

Clinical criteria for those with known exposure include symptoms consistent with acute or lower respiratory tract infection, with or without conjunctivitis, or "acute respiratory illness without an identified cause."

If a patient meets epidemiological or clinical criteria for exposure to the A(H5N1) virus, clinicians should collect a sample and report to their state health department, which should notify CDC within 24 hours about a potential "case under investigation," the agency said.

While the CDC acknowledged that bird-to-human transmission of the A(H5N1) strain has occurred previously, this is the first symptomatic bird-to-human transmission reported in this most recent outbreak. Previously, there was an asymptomatic case in the U.K. reported in an individual exposed to "domestically kept infected ducks."

Still, they stressed that "there is no evidence of sustained human-to-human transmission" of this virus in the U.S.

Case Details

The agency provided more details about the case following its , including hedging as to whether or not the person was actually infected with the bird flu strain or whether it was due to "transient surface contamination of the individual's nasal passages." The person reported fatigue as their only symptom, which resolved after 3 days.

However, the CDC noted that the case is being treated like an infection, and the patient was given oseltamivir and remains asymptomatic and in isolation.

The agency explained that the individual was "participating in poultry depopulation activities" and reported "wearing recommended personal protective equipment," though the level of eye protection was unclear. An upper respiratory tract specimen tested positive for influenza A, but negative for the A(H3N2) or A(H1N1pdm09) strains. The H5N1 strain was confirmed via testing at CDC via RT-PCR, the agency said.

Specimens from the patient's close contacts were also collected, and all tested negative for influenza.

The CDC recommended that the public avoid "unprotected exposure" to sick or dead birds, bird feces, or other contaminated material.

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