Transmission of avian influenza A(H7N9) virus from father to child: a report of limited person-to-person transmission, Guangzhou, China, January 2014

We investigated a possible person-to-person transmission within a family cluster of two confirmed influenza A(H7N9) patients in Guangzhou, China. The index case, a man in his late twenties, worked in a wet market that was confirmed to be contaminated by the influenza A(H7N9) virus. He developed a consistent fever and severe pneumonia after 4 January 2014. In contrast, the second case, his five-year-old child, who only developed a mild disease 10 days after disease onset of the index case, did not have any contact with poultry and birds but had unprotected and very close contact with the index case. The sequences of the haemagglutinin (HA) genes of the virus stains isolated from the two cases were 100% identical. These findings strongly suggest that the second case might have acquired the infection via transmission of the virus from the sick father. Fortunately, all 40 close contacts, including the other four family members who also had unprotected and very close contact with the cases, did not acquire influenza A(H7N9) virus infection, indicating that the person-to-person transmissibility of the virus remained limited. Our finding underlines the importance of carefully, thoroughly and punctually following-up close contacts of influenza A(H7N9) cases to allow detection of any secondary cases, as these may constitute an early warning signal of the virus's increasing ability to transmit from person-to-person.