This week it was announced that the virus has acquired mutations that could make it a much bigger problem.
H7N9 mainly infects birds and doesn’t readily pass from human to human, but should it acquire this ability a deadly pandemic could ensue (for more on how to tackle the next pandemic, see ““).
The virus spreads in poultry without making birds visibly sick, so it is often only found when people fall ill. But this week both mainland China and Taiwan reported human cases in which a surface protein on the virus has a mutation that makes it lethal to chickens. If that spreads, H7N9 will be .
While the mutation doesn’t make people any more sick, it allows the virus to replicate much faster in chickens. With more in circulation, people, and perhaps pigs and other mammals, are more likely to catch it. Each case is a chance for H7N9 and perhaps become better at spreading from person to person.
Our only real defence is a vaccine. Last week, China launched clinical trials of four strains by a state-owned vaccine firm. But even if the vaccine works, the world can’t yet make enough to cope with a pandemic.