Avian influenza viruses can circulate for months before they are detected. This was shown by the genetic analysis of the outbreak of avian influenza in China between 2013 and 2017. Therefore, the researchers recommend continuous monitoring of the health of the animals.
“Our results confirm that it is best not to wait until cases of avian influenza occur, because the virus may have circulated for much longer,” study leader Tanja Stadler said in a statement issued by the Swiss Federal Institute of Technology in Zurich (ETH Zurich) on Friday. . Instead, according to the epidemiologist, sanitary surveillance should be carried out in stables and live poultry markets at regular intervals.
The ETH researchers came to this conclusion by analyzing the H7N9 strain of avian influenza, which was rampant in China between 2013 and 2017 and affected not only poultry but also humans. A total of 616 people in China were found to have died from infection with this subtype. The results were recently published in the journal PNAS.
Lineage analyzes showed that the H7N9 virus must have been circulating in poultry for several months before it was detected. The researchers were also able to show that poultry markets were affected significantly more than previously assumed. Outbreaks have been difficult to detect, especially in 2013-2016, when the virus was causing almost no symptoms in poultry.
According to the researchers, the virus then changed and caused severe disease symptoms in poultry. This made it easier to identify affected chicken farms.
In 2017, the country began vaccinating poultry against the pathogen. Together with intensive hygiene measures in poultry markets, the authorities managed to weaken the epidemic in animals and significantly reduce transmission of infection to humans. According to experts, since the genome of viruses is constantly changing, there is still a certain risk that the H7N9 virus will become dangerous to humans again.
