The United States has reopened its borders to vaccinated international travelers, ending a 20-month travel ban at the same moment Europe is battling a surge of Covid-19 cases that has pushed the continent back into the epicenter of the pandemic.

Fully vaccinated travelers from 33 countries — including the United Kingdom and much of Europe — can now enter the US without needing to quarantine, provided they have proof of vaccination and a negative viral test.

Families and friends separated since the start of the pandemic streamed into airports across major European cities on Monday morning, excited to see loved ones for the first time since former President Donald Trump imposed tough travel restrictions at the outset of the pandemic in an effort to control the virus.

But beyond these happy scenes is a darker backdrop.

Europe is in the grip of a fresh wave of coronavirus cases, with the World Health Organization last week warning the region is once again “at the epicenter” of the pandemic.

Large swathes of Europe are battling to beat back surges of the Delta variant, amid the relaxation of restrictions and stuttering vaccine rollouts in some countries, with the WHO warning half a million Europeans could die with Covid-19 in a potentially devastating winter.

Germany on Monday recorded its highest seven-day incidence rate since the pandemic began. The same day, neighboring Austria banned unvaccinated people from restaurants and hotels amid a surge in cases. Iceland has also reintroduced masks and social-distancing rules following a rise. And cases are hovering at record levels in Russia, Ukraine and Greece.