Avian to Human Transmission of H7N9 Flu Virus Identified

THURSDAY, April 25 (HealthDay News) -- The influenza A H7N9 virus has been transmitted from birds (specifically, chicken) and sickened humans, according to a study published online April 25 in The Lancet.

Yu Chen, M.D., from Zhejiang University in China, and colleagues studied hematological, biochemical, radiological, and microbiological findings from four hospitalized patients (mean age, 56 years) with new-onset respiratory symptoms, unexplained radiographic infiltrate, and laboratory-confirmed H7N9 virus infection (March 7 to April 8, 2013). Throat and sputum samples were analyzed with reverse transcriptase-polymerase chain reaction to detect M, H7, and N9 genes. Cloacal swabs from 86 birds were also analyzed.

The researchers found that the patients, all of whom had contact with poultry three to eight days before disease onset, presented with fever and rapidly progressive pneumonia that did not respond to antibiotics. Other clinical characteristics included being leucopenic and lymphopenic, and having impaired liver or renal function, substantially increased serum cytokine or chemokine concentrations, and disseminated intravascular coagulation with disease progression. Two patients died. Sputum specimens were more likely than throat swabs to test positive for the H7N9 virus, and the patients' viral isolates were similar to that from an epidemiologically-linked market chicken. All viral gene segments were of avian origin. H7 isolated viruses most closely resembled the H7N3 virus from domestic ducks in Zhejiang, while the N9 virus was most similar to the wild bird H7N9 virus in South Korea. In the human H7 virus, the Gln226Leu and Gly186Val substitutions were present, as was the PB2 Asp701Asn mutation. In viral M2, the Ser31Asn mutation was present.

"Cross species poultry-to-person transmission of this new reassortant H7N9 virus is associated with severe pneumonia and multiorgan dysfunction in human beings," the authors write.

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