Data were collected by the Chinese CDC on households to study human-to-human transmissibility of the avian influenza A (H7N9) virus in China.
Household contact information was collected for 125 index cases during the spring wave (Feb to May 2013), and for 187 index cases during the winter wave (Oct 2013 to Mar 2014). Using a statistical model, the workers found evidence for human-to-human transmission, but such transmission is not sustainable. They estimated that the household secondary attack rate among humans to be 1.4% (range 1.3% to 2.2%). There was no significant change in the human-to-human transmissibility between the two waves, although a minor increase was observed in the winter wave. No sex or age difference in the risk of infection from a human source was found. Human-to-human transmissibility of H7N9 continues to be limited, but it needs to be closely monitored for potential increase via genetic reassortment or mutation.
The article can be found at: Euro Surveill. 2015;20(10):pii=21056. http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=21056