First human infections with avian influenza H7N9 virus

Fourteen people in China have been infected with avian influenza H7N9 virus, leading to five deaths. This avian influenza virus has never been isolated from humans. Influenza A viruses with the H7 hemagglutinin protein circulate among birds, and some, such as H7N2, H7N3, and H7N7, have been previously found to infect humans. It is not known how the individuals in China acquired the H7N9 virus. Some of the infections have occurred in Shanghai, where a similar virus was found in pigeon samples collected at a marketplace in that city. It is not clear what types of pigeon samples tested positive for the virus, nor is it known whether the virus spread from poultry to pigeons or vice versa. In response the city has begun mass slaughter of poultry to stem further spread of the virus. Influenza H7N9 virus is typically a low-pathogenicity virus, which means that infection of chickens causes mild respiratory disease, depression, and decrease in egg production. The virus does not have a basic peptide between HA1 and HA2. The presence of a basic peptide in this location allows the viral hemagglutinin glycoprotein to be cleaved by proteases that are present in most cells, enabling the virus to replicate in many organs. Without this basic peptide, the HA is cleaved only by proteases present in the respiratory tract, limiting replication to that site. According to Brian Kimble on Google+, the nucleotide sequence reveals that the H7N9 human isolate is a reassortant* with 6 RNA segments enco...
Source: virology blog - Category: Virology Authors: Tags: Basic virology Information avian influenza China h7n9 H9N2 HA hemagglutinin pandemic reassortant Shanghai viral virus Source Type: blogs