A deadly type of bird flu known to be transmissible to humans, called H7N9, seems to be breaking out again this flu season in China. H7N9 has caused only modest outbreaks since 2013, the year it was first identified (see this blog, Apr. 17, 2013). The intensity of yearly H7N9 outbreaks peaked in 2014 and then seemed to decline in 2015 and 2016, leading some health officials to think that the worst was over. Not so, it seems. The current 2017 outbreak of H7N9 (which began in October, the typical start of the winter flu season) is the worst outbreak yet. According to the World Health Association (WHO), more than a third of all cases of H7N9 flu ever recorded have occurred during this year's outbreak, and flu season isn't over.
H7N9 bird flu is not easily transmitted from birds to humans, but it is quite virulent. The death rate from confirmed H7N9 infections in humans is nearly 40%. So far, there are no confirmed cases of human-to-human transmission. Health officials worry that if/when the virus mutates in a way that makes it easily transmissible between humans, we could face a worldwide pandemic.
For now, H7N9 outbreaks have been confined to China, where close contact with poultry is much more common than it is in this country. Are we prepared for a H7N9 bird flu pandemic? The short answer is "no". At the moment there is no vaccine against it. Let's hope that a change to human-to-human transmission of H7N9 doesn't develop anytime soon.
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