Australia’s second most populous state Victoria entered a five-day lockdown on Feb. 13 as authorities raced to prevent a third wave of Covid-19 cases sparked by the highly infections UK variant.

Australian authorities said mandatory hotel quarantine for people arriving for the Australian Open tennis tournament was essential to stop Covid-19, as the country recorded another day with no new locally acquired cases on Jan. 19.

Coronavirus infections rose above 13 million across the world on Monday, according to a Reuters tally, climbing by one million in just five days in a pandemic that has killed more than half a million people.

Australian officials are closing the border between Australia’s two most populous states for an indefinite period as they scramble to contain an outbreak of the coronavirus in the city of Melbourne.