Bird flu virus H7N9 massively spread in China

Deliberate spread of the bird flu pathogen H7N9 in China

03/12/2015

The massive spread of the H7N9 avian influenza virus in China is increasingly worrying medical professionals worldwide. „Nobody knows if H7N9 avian influenza, which has infected more than 560 people in China and killed 204, could continue to evolve, making it easier to spread among humans“, reports the trade magazine „Nature“.

An international team of researchers led by Yi Guan and Huachen Zhu of Shenzhen's Third People's Hospital came to the conclusion that the virus is widespread in China's poultry population and high risk of recurrence in the largest H7N9 study to date in China People exists. The researchers warn that it is only a matter of time until the virus spreads through poultry movement in the context of cross-border trade beyond China, as had previously done with the influenza viruses H5N1 and H9N2. The experts also see the H7N9 virus at high risk of developing mutations that would facilitate easier transmission between humans and thus lead to a pandemic.

First outbreak in 2013
After H7N9 was first detected in and around Shanghai at the end of March 2013, this outbreak was brought under control relatively quickly. But in the following winter, the virus spread in southern China again, causing a second major wave of human infection. These also ebbed away in the summer of 2014, followed until the end of last year the next big outbreak, which is still in progress. The international research team led by Yi Guan monitored the spread of the H7N9 virus from October 2013 to July 2014 by taking pharyngeal swabs from poultry on 15 Chinese cities and performing a genomic study. In samples from seven cities or in three percent of the total samples taken, they were able to prove the pathogens.

Poultry trade promotes the spread of H7N9
The researchers report that H7N9 viruses appear to have spread along trade routes and were found in chickens but not ducks. „Repeated introduction of viruses from Zhejiang into other provinces and the presence of H7N9 viruses in poultry markets have fueled the recurrence of human infections“, report Guan and colleagues. The rapid expansion of the geographical distribution and genetic diversity of H7N9 viruses is „a direct challenge to current disease control systems.“ The genomic analysis had also revealed that a variety of genetic variants of the virus circulate and that the second major outbreak was significantly triggered by several pathogens, which were derived from a pathogen of the first wave of infection.

Pandemic risk difficult to estimate
Genetic surveillance of H7N9 spread is important, according to the researchers, to detect mutations early and to identify influenza strains that are increasingly spreading in mammals. Because sometimes they also pose an increased risk for people. This is the case with the H7N9 virus and many have already discussed the pandemic potential of the pathogen. However, the now observed spread and diversity of H7N9 viruses within China is not automatically associated with increased pandemic risk. It was „practically impossible“ To determine if this increased diversity increases the risk of developing a pandemic virus, Guan said. To a similar assessment comes Thorsten Wolff of the Berlin Robert Koch Institute (RKI) to the news agency „dpa“. Thus, the study results are not an acute cause for concern, because only when the pathogens spread among people threaten a pandemic. Give for this „There is currently no evidence, thank God“, quotes the „dpa“ the experts. (Fp)