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Low risk for bird-to-human transmission of HPAI H5 viruses
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Recently published data suggested that transmission of newly emerged, highly pathogenic avian influenza viruses from birds to humans in certain exposure settings was uncommon.
From December 2014 to March, 60 outbreaks of highly pathogenic avian influenza (HPAI) A H5 viruses were reported in wild, captive and domestic birds in 13 states. To determine the risk for animal-to-human HPAI H5 virus transmission in the United States, researchers contacted state and local health departments near these outbreaks to request information on human exposures.
Along with symptoms and the circumstances of potential exposures, respiratory specimens from patients displaying acute respiratory infection symptoms, defined as two or more symptoms, were collected and tested by real-time reverse transcription (rRT-) PCR. Of the 164 persons identified as exposed to infected birds, the researchers obtained exposure information for 60 of them.
Among exposed persons, five developed an acute respiratory infection within 10 days of their last contact with the infected birds. Four of these patients tested negative for the influenza virus by rRT-PCR. The other patient had serologic evidence of seasonal influenza A(H3N2) virus infection, but no evidence of an HPAI H5 virus.
“Although this early assessment suggests that the risk of bird-to-human transmission of HPAI H5 viruses in the United States may be low, the CDC recommends vigilance when considering future human exposures to birds that are or may be infected,” the researchers wrote.
The investigators recommended that persons exposed to HPAI-infected birds be monitored for 10 days after the last exposure and be tested for influenza promptly if respiratory symptoms develop. They also suggested that, despite the low risk for transmission, each exposure incident should be reported and investigated by animal and human health partners.
“A rapid response to any potential human cases of HPAI H5 infection in the United States is critical to prevent further cases, evaluate clinical illness, and assess the ability of these viruses to spread among humans,” the researchers concluded. – by Tina DiMarcantonio
Disclosure: The researchers report no relevant financial disclosures.
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