The H7N9 has possibility to evolve, form future pandemic: HKU study

The University of Hong Kong (HKU) released the result of a recent study on Friday, suggesting that there's possibility for the H7N9 virus to transmit among human and to evolve further, forming a future pandemic threat.

H7N9, the human-isolated avian influenza A, has caused 131 cases of infection in mainland China and Taiwan and took 36 lives in the past 2 months

Through experiments on animals, HKU's research proves that the virus can cause significant infection in ferrets, which have similar clinical signs, transmission route and pathology to humans. It also shows that the clinical signs caused by the H7N9 are similar to those of the pandemic swine flu (H1N1) 2009 virus.

2-3 cases of "Family Cluster" in the Chinese mainland aroused the concerns towards the potential risks of human-to-human transmissibility. However, no hard evidence suggesting that the virus had been transmitted among humans, said Guan Yi, professor at the Li Ka Shing Faculty of Medicine of HKU, who led the study.

The study shows that the H7N9 virus can transmit via direct contact and air-borne exposure among ferrets and cause symptoms including fever, nasal discharge and pneumonia etc..

"The transmission via air-borne exposure of H7N9 is limited," Guan said. "I will score '1' in the range of '1-10' to assess the current transmissibility of the virus, according to our recent study."

"I believe there could be a second outbreak of H7N9 among poultry," Guan added, "if the virus could evolve and acquire human-to-human transmissibility, the basis of a future pandemic threat would be formed."

"The clinical signs caused by the virus are relatively mild," said Zhu Huachen, research assistant professor at the Li Ka Shing Faculty of Medicine of HKU. "The infected ferrets fully recover at 14 to 16 days and specific antibodies against the virus appear since day 7."

As to people infected with H7N9 who had been observed with more severe symptoms, Zhu said that some personal factors, including aging or other underlying medical conditions would contribute to the patients' deteriorating states of illness.

"We believe that asymptomatic infections among human are possible," Zhu said, "since in our experiments, the infected animals do not necessarily develop fever and other related clinical signs." Zhu noted that the asymptomatic infections could be easily ignored, developing into more severe conditions or transmit to others.

The research team also discovers that with inefficient transmissibility, the H7N9 virus can also infect pigs. "The risk for the virus to evolve further could be increased enormously if H7N9 was binding with other virus," Zhu said, "the swine influenza virus for instance."

"Since the virus has the possibility to infect mammals," Zhu said, "we suggest the health authority should also take into consideration of other poultry and pets which may have a chance to be contacted with the virus."