Genetic analysis indicates that, in one instance, the novel avian influenza H7N9 virus was transmitted between people, Chinese researchers report in the British Medical Journal.
Using rRT-PCR, viral culture, and a hemagglutination inhibition assay, the researchers examined samples from two infected patients — father and daughter — their contacts, and their environment. Based on both sequence and phylogenetic analysis, the team determined that the strains were "almost identical."
The researchers note that the index patient, the father, likely contracted the virus from a live poultry market where he shopped for the whole family; the daughter did not visit that, or other, markets. Instead, the researchers suspect she was infected with the flu virus as she cared for her father in the hospital. Both patients died.
"We believe that the most likely explanation for this family cluster of the two patients with novel avian influenza H7N9 virus infection is that the virus transmitted directly from the index patient to his daughter," the researchers say.
However, they add that none of the patients' other contacts appeared to have become ill with the flu, indicating that the virus is not easily transmitted between people.
"Does this imply that H7N9 has come one step closer towards adapting fully to humans?" James Rudge and Richard Coker write in a related editorial. "Probably not. Crucially, there is still no evidence of sustained transmission among humans."