The state of Victoria, Australia, announced a seven-day lockdown beginning Thursday night to stem a coronavirus outbreak in the northern suburbs of Melbourne, the country’s second-most populous city, after Sydney.
After nearly three months without a new infection, state health officials have detected 26 cases in the Melbourne-area cluster. The outbreak is believed to have begun when a man became infected while serving a 14-day hotel quarantine in the city of Adelaide, then traveled to Melbourne, where he tested positive for the virus.
The authorities said that more than 10,000 primary and secondary contacts had been identified, as they rushed to trace contacts at dozens of sites where people may have been exposed. Officials said that the virus circulating in the Melbourne area was the variant first detected in India.
“In the last day, we’ve seen more evidence that we’re dealing with a highly infectious strain of the virus, a variant of concern which is running faster than we have ever recorded,” James Merlino, the acting premier of Victoria, told reporters on Thursday morning.
Australia has all but eliminated community transmission of the virus, but several smaller outbreaks this year have led cities and states to impose temporary lockdowns. Mr. Merlino said that this outbreak, one of the largest in recent months, was partly the result of a sluggish vaccination campaign that has left a large proportion of Australians exposed to new strains of the virus. Less than 2 percent of Australia’s 25 million people have been fully inoculated.
“If more people were vaccinated we might be facing a very different set of circumstances,” he said. “That is a fact.”
Others criticized the Australian government for failing to implement an effective quarantine system and relying on hotels to house incoming travelers.
In a report released this week, the authorities said that the man first diagnosed in Melbourne most likely contracted the virus after he and another infected guest opened their hotel room doors within minutes of each other, allowing the virus to spread by aerosol transmission between their rooms.
“This is the 17th outbreak from hotel quarantine in just the last six months,” Mark Butler, the opposition health minister, told the Australian Broadcasting Corporation on Thursday. “We’re dealing with these outbreaks almost every week or two at the moment.”
Mr. Butler said that Australia’s prime minister, Scott Morrison, had failed to heed the advice of experts who called for the government to set up dedicated quarantine facilities “to take the pressure off hotels that were built for tourism.”
Last year, after an infection in a quarantine hotel led to an outbreak in the state, Melbourne’s five million residents endured one of the longest lockdowns in the world, lasting 111 days.
Under the new lockdown, Victorians are restricted from leaving their homes except to shop, work, exercise, care for others or get vaccinated.
Speaking to reporters on Thursday, Mr. Morrison warned that the lockdown was a grave reminder of how rapidly the virus could resurge.
“There are no certainties, there are no guarantees, in a global pandemic, and against a virus, an insidious virus such as this,” he said.