Avian influenza H7N9 mutates further!

Wednesday, 29 May, 2013

Bad news! Influenza H7N9 is evolving fast. In a paper published in the Lancet online today Hu et al (2013) report genetic resistance to nueraminidase inhibitors, oseltamivir and zanamivir. They demonstrated that patients with resistant genotypes had higher viral loads, more severe illneess and poorer clinical outcomes. In one patient they found no genetic resistance in H7N9 on admission, but in an isolate after 9 days of antiviral therapy mutation conferring resistance to neuraminidase inhibiotors had appeared!

Hu et al (2013) also showed that viral loads in throat swabs remained high in the first week of infection unlike the usual human influenzas where they decline fairly quickly. If H7N9 does acquire the ability to trnsmit human-to-human, we may see a repeat of the SARS-scenario where high numbers of cases were health care workers. Time to make sure that infection control procedures are working well.

The only good news is that the number of cases in China has dropped since authorities prohibited sale of live chickens in markets. But don't be fooled; H7N9 has not gone away!


Hu et al. Association between adverse clinical outcome in human disease caused by novel influenza A H7N9 virus and sustained viral shedding and emergence of antiviral resistance. Lancet 2013; published online 29 May 2013.

Posted by Rick Speare