In early May, two people quarantined in adjacent hotel rooms in the Australian city of Adelaide opened their doors within seconds of each other to collect meals. Health authorities believe that could have been enough for the virus to spread from a man in one of the hotel rooms to a man in the other via airborne transmission.

The man who was believed to be infected at the hotel then traveled to Melbourne, leading to an outbreak and a lockdown of Australia’s second-largest city, health authorities say.

Cases like those and the spread of highly infectious new coronavirus strains are prompting officials in some countries to rethink whether hotels are the best place to quarantine returning travelers, even as the U.S. and Europe weigh easing travel restrictions as vaccination levels rise.

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Australia and China are planning new, specially designed quarantine centers that public-health experts say will be more effective at stopping the virus from leaking out. Others, such as New Zealand, are considering similar steps.

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All three countries have used hotel quarantines, among other pandemic safety measures, to keep case numbers much lower than those elsewhere. But the new variants are so transmissible that health experts are now worried the virus could leak out easier and require harsher lockdowns to control, particularly in places such as Australia and New Zealand where the vaccine rollout has been relatively slow. Australia has fully vaccinated about 9% of its population and New Zealand about 10%, according to Our World in Data, which also shows about 16% of China’s population was fully vaccinated by June 10—though China’s National Health Commission reports the country has administered half a billion doses since then.

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"It’s finally sunk in that the virus is going to be circulating for a long time yet, and the new and highly transmissible variants may make hotel-style quarantine difficult to operate safely," said Amanda Kvalsvig, an epidemiologist at the University of Otago, Wellington in New Zealand. "The challenges of preventing transmission in hotel settings have put both staff and guests at risk of infection."

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