Credit: Antoine Doré

For a disease that can resemble the common cold, influenza packs a powerful — and sometimes lethal — punch. As many as half-a-million people around the world die annually from flu. The culprit is a virus that mutates to evade our immune systems, leaving vaccines and therapies scrambling to keep up. In some years, a mutation creates a pathogen that is particularly nasty, resulting in pandemic flu. Last year marked 100 years since the 1918 ‘Spanish flu’ pandemic, which killed at least 50 million people worldwide. In 2009, another pandemic swept across the world at frightening speed, and in 2017–18 so-called seasonal flu (not considered a pandemic) hit hard in the United States.

Vaccines are the first line of defence against flu. Researchers have made it a top priority to develop a vaccine that protects against as many strains of the virus as possible. And because speed is of the essence in mounting a response to flu, new methods are being pursued to speed up vaccine production. If prevention fails, there is only a limited arsenal of antiviral drugs to treat flu, although researchers are working to develop more. But it is a never-ending battle, as the wily virus mutates its way to resistance.

Treatment, of course, depends on diagnosis. For individual patients, molecular tests can now give conclusive results more quickly than older methods, but adoption of the new tests has been slow, partly because of their high cost. On a public-health level, it is important to know when and where an outbreak is under way — a task made easier by information technology. And because some of the most dangerous flu viruses make the leap from animals to humans, researchers are studying how to monitor the disease on farms and in wild bird populations.

We are pleased to acknowledge the financial support of Sanofi Pasteur in producing this Outlook. As always, Nature retains sole responsibility for all editorial content.