HealthDay News — A father and daughter who both died this spring from H7N9 avian influenza provide the first evidence that the novel strain can be transmitted from person to person, researchers reported.

The father became ill in early March, five to six days after his last exposure to poultry, and was cared for by his 32-year-old daughter, who had no known exposure to poultry and became ill six days after contact with her father, Xian Qi, PhD, of the Jiangsu Province Center for Disease Control and Prevention in Nanjing, China, and colleagues reported in BMJ.

Both patients died, and the two viral strains isolated from them were nearly genetically identical. However, no infection was detected among the 43 close contacts of both patients, suggesting human-to-human transmission is “limited and nonsustainable.”

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The majority of the 134 laboratory-confirmed cases of H7N9 avian influenza have not been epidemiologically related, but investigators suspected human-to-human transmission in two small clusters — the father and daughter in this study and a separate cluster involving a man, his father and his brother.

Lab investigations indicated the genetic sequences of all eight viral genes from the two H7N9 strains isolated from the father and daughter were nearly identical, with similarity ranging from 99.6% to 99.9%, the researchers found.

“While the paper by Qi and colleagues might not suggest that H7N9 is any closer to delivering the next pandemic, it does provide a timely reminder of the need to remain extremely vigilant: the threat posed by H7N9 has by no means passed,” James Rudge, PhD and Richard Coker, MD, both of the London School of Hygiene and Tropical Medicine unit in Bangkok wrote in an accompanying editorial.


  1. Qi X, et al. BMJ. 2013; 347: f4752.
  2. Rudge JW and Coker R. BMJ. 2013; 347: f4730.