It was barely a month ago that the Covid-19 variant Omicron was first spotted by scientists. In just a few weeks, the highly transmissible variant has reached almost every country in the world, and cases are now surging in continental Europe and parts of South Africa.

The rapid spread means that Omicron is set to replace Delta as the variant that causes the most Covid-19 cases globally. Research suggests that it may be better at getting into human cells, as well as evading immunity from vaccinations or earlier infections. This has prompted some governments to impose new rules, including restrictions on international travel. But travel limits alone will not be enough to contain the spread of the variant.