Omicron has reached at least 13 countries despite travel curbs

The Omicron variant, first sequenced in South Africa, has been identified in at least 12 other countries. Most have so far reported imported cases spotted in travelers from the African nation and other places. Still, the spread shows the difficulties of curtailing new strains of Covid-19.

Israel, for instance, said a confirmed case who arrived from Malawi rode on a bus from Tel Aviv. Italy’s first case traveled around the country for days before testing positive.

Researchers worldwide are racing to understand the full impact of the new strain and governments have banned travelers from South Africa and nearby countries on concerns Omicron could evade the protection of vaccines or fuel new Covid surges.