Transmission of avian H9N2 influenza viruses in a murine model.

Avian H9N2 influenza viruses have circulated widely in domestic poultry around the world, resulting in occasional transmission of virus from infected poultry to humans. However, it is unknown whether H9N2 influenza virus has acquired the ability to be transmitted from human to human. Here, we report that mouse-adapted H9N2 influenza viruses can replicate efficiently and are lethal for several strains of mice. To evaluate the transmissibility of mouse-adapted H9N2 influenza viruses, we carried out transmission studies in mice using both contact and respiratory droplet routes. Our results indicate that mouse-adapted H9N2 influenza viruses can replicate efficiently and be transmitted between mice. This suggests that once H9N2 influenza viruses adapt to new host, they should present potential public health risks, therefore, urgent attention should be paid to H9N2 influenza viruses. Copyright 2009 Elsevier B.V. All rights reserved.