Genetic Analysis and Rescue of a Triple-reassortant H3N2 Influenza A Virus Isolated From Swine in Eastern China

One influenza H3N2 virus, A/swine/Shandong/3/2005 (Sw/SD/3/2005), was isolated from pigs with respiratory disease on a farm in eastern China. Genetic analysis revealed that Sw/SD/3/2005 was a triple-reassortant virus with a PB2 gene from human-like H1N1, NS from classical swine H1N1, and the remaining genes from human-like H3N2 virus. These findings further support the concept that swine can serve as reservoir or mixing vessels of influenza virus strains and maintain genetic and antigenic stability of viruses. Furthermore, we have successfully established a reverse genetics system based on eight plasmids and rescued Sw/SD/3/2005 through cell transfection. HI tests and RT-PCR confirmed that the rescued virus maintained the biological properties of the wild type Sw/SD/3/2005. The successful establishment of the reverse genetics system of Sw/SD/3/2005 will enable us to conduct extensive studies of the molecular evolution of H3N2 influenza viruses in swine.

Severe human infection with a novel avian-origin influenza A(H7N4) virus

Human infections with influenza H7 subtypes, such as H7N9, have raised concerns worldwide. Here, we report a human infection with a novel influenza A(H7N4) virus. A 68 years-old woman with cardiovascular and cholecystic comorbidities developed rapidly progressed pneumonia with influenza-like-illness as initial symptom, recovered after 23 days-hospitalization including 8 days in ICU. Laboratory indicators for liver and blood coagulation dysfunction were observed. Oseltamivir phosphate, glucocorticoids and antibiotics were jointly implemented, with nasal catheterization of oxygen inhalation for this patient.We obtained the medical records and collected serial respiratory and blood specimens from her. We collected throat, cloacal and/or feces samples of poultry and wild birds from the patient's backyard, neighborhood, local live poultry markets(LPMs) and the nearest lake. All close contacts of the patient were followed up and sampled with throat swabs and sera. Influenza viruses and other respiratory pathogens were tested by real-time RT-PCR, viral culturing and/or sequencing for human respiratory and bird samples. Micro-neutralizing assay was performed for sera. A novel reassortant wild bird-origin H7N4 virus is identified from the patient and her backyard poultry(chickens and ducks) by sequencing, which is distinct from previously-reported avian H7N4 and H7N9 viruses. At least four folds increase of neutralizing antibodies to H7N4 was detected in her convalescent sera. No samples from close contacts, wild birds or other poultry were tested positive for H7N4 by real-time RT-PCR.