Increasing toll of H7N9 bird flu demands constant vigilance

A big wave of H7N9 bird flu cases and deaths in China since the start of 2014 is a reminder that emerging flu strains need constant surveillance if the world is not to be caught off guard by a deadly pandemic.
At least 24 H7N9 flu infections and three deaths have been confirmed in the past week by the World Health Organization (WHO), a dramatic increase on the two cases and one death reported for the four-month summer period of June to September.
“There’s now a clear second wave of this virus,” said Jake Dunning, a researcher at Imperial College London who has been monitoring the outbreak.
While the winter flu season means an increase in infections is not unexpected, it also raises the risk of the virus mutating and perhaps getting a chance to acquire genetic changes that may allow it to spread easily from one person to another.
The H7N9 bird flu virus first emerged in March last year and has so far infected at least 170 people in China, Taiwan and Hong Kong, killing around 50 of them.
Many but not all of the people infected have had previous contact with poultry or other birds, so for now, the fact that this virus has apparently not adapted to easy human-to-human transmission is one of the main features keeping a pandemic emergency response on hold.
Yet the strain already has several worrisome features, including a limited capability to spread from one person to another.
Several clusters of cases in people who had close contact with an initially infected person have been reported in China. A scientific analysis of probable H7N9 transmission from person to person, published last August, gave the best proof yet that it can sporadically jump between people.
A separate team of researchers in the United States said in December that while it is not impossible that H7N9 could become easily transmissible from person to person, it would need to undergo multiple mutations to do that.
Another alarm was sounded, also last month, when scientists said they had found that a mutation in the virus can render it resistant to a key first-line treatment drug without limiting its ability to spread in mammals.
WHO chief spokesman Gregory Hartl said the United Nations health agency had noted the rapid increase in infections in the past few weeks and is keeping a watchful eye.