Highly pathogenic H7N9 avian influenza, detected in people for the first time in China in 2013, have a slightly increased binding preference for human airway receptors compared with the low-pathogenic form, a research team from China reported today in Eurosurveillance.
The scientists also found that highly pathogenic H7N9 containing the R292K substitution was resistant to multiple antivirals, requiring urgent further assessment. In January, Taiwan reported a resistance mutation in an imported case involving a patient infected with highly pathogenic H7N9.
For their study, the researchers compared high-path H7N9 genetic sequences from patients infected earlier this year in Guangdong province with low-pathogenic H7N9 and highly pathogenic H5N6.
Compared with low-path H7N9, the highly pathogenic form showed slightly increased binding preference for the types of receptors found in human upper and lower airways. The researchers said high-path virus's persistent preference for both avian and human receptors may result in their circulation in poultry and possible transmission among people.
The team confirmed that the high-path viruses showed little or no response to antibodies against the low-path H7N9 vaccine strain. The World Health Organization has already recommended a new candidate vaccine strain for the new form of the virus.
In their analysis of antiviral resistance, the investigators found that high-path H7N9 that contained the R292K substitution in the neuraminidase protein showed resistance to oseltamivir (Tamiflu), zanamivir (Relenza), and peramivir. They said the virus had the ability to acquire the substitution as early as 2 days after the administration of the antiviral drugs.
They concluded that highly pathogenic H7N9 doesn't pose an enhanced risk solely to poultry; it also has implications for human health surveillance and control strategies. The authors also said their findings are a reminder of the crucial role of antiviral surveillance monitoring as a key component of pandemic preparedness.