A woman stands near chickens at a chicken farm in Zouping, east China's Shandong province on April 1, 2013. AFP PHOTOAFP/AFP/Getty Images
It has been about half a year since H7N9 – a new variety of bird flu – first emerged in Shanghai and triggered an intense, two-month-long cascade of infections across eastern China.
But cases began tapering off in May and the summer only saw three newly-reported infections. No new cases have been reported since August 11 and attentions have largely shifted back towards the Middle East, where another deadly and newly-emergent virus, MERS, continues to cause concern.
While it may feel as though H7N9 has vanished, infectious disease experts know this is probably not the case. And sure enough, the World Health Organization today announced the first H7N9 infection in two months:
The patient is a 35-year-old man from Zhejiang Province. He was admitted to a hospital on 8 October 2013 and is in a critical condition. Additionally, a previously laboratory-confirmed patient from Hebei has died.
To date, WHO has been informed of a total of 136 laboratory-confirmed human cases with avian influenza A(H7N9) virus infection including 45 deaths. Currently, three patients are hospitalized and 88 have been discharged. So far, there is no evidence of sustainable human-to-human transmission.
Whether this is a one-off infection or the front edge of another H7N9 season – that remains to be seen. Perhaps the world will just continue to see sporadic H7N9 cases in the years and decades to come.
But it is not unreasonable to expect that there could be more cases as the winter approaches; we know flu viruses have seasonal patterns and avian flu viruses are no different. As the U.S. Centres for Disease Control and Prevention says:
Studies indicate that avian influenza viruses have a seasonal pattern to them, much like human seasonal influenza viruses. If this is the case, H7N9 infections – in birds and people – may pick up again when the weather turns cooler in China.