After entire countries were shut down during the first surge of the coronavirus earlier this year, some governments are trying more targeted measures as cases rise again around the world, especially in Europe and the Americas.
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Spanish officials have limited travel to and from some parts of Madrid before restrictions were widened throughout the capital and some suburbs.
Italian authorities have sometimes quarantined spots as small as a single building.
While countries including Israel and the Czech Republic have reinstated country-wide closures, other governments hope smaller-scale shutdowns can work this time in conjunction with testing, contact tracing and other initiatives.
The concept of containing hot spots isn't new but it's being tested under new pressures as authorities try to avoid a dreaded resurgence of illness and deaths, this time with economies weakened from earlier lockdowns, populations chafing at the idea of renewed restrictions and some communities complaining of unequal treatment.
Confirmed world coronavirus infections surpassed 40 million on Monday, according to a Johns Hopkins University tally.
Some scientists say a localised approach, if well-tailored and explained to the public, can be a nimble response at a complex point in the pandemic.
"It is pragmatic in appreciation of 'restriction fatigue'... but it is strategic, allowing for mobilisation of substantial resources to where they are needed most," says Dr Wafaa El-Sadr, who is following New York City's efforts closely and is on some city advisory boards.
Other scientists are more wary.
"If we're serious about wiping out COVID in an area, we need coordinated responses across" as wide a swath as possible, says Benjamin Althouse, a research scientist with the Institute for Disease Modeling in the US.
In a study that has been posted online but not published in a journal or reviewed by independent experts, Althouse and other scientists concluded that amid patchwork coronavirus-control measures in the US in the northern spring, some people travelled farther than usual for such activities as worship, suggesting they might have responded to closures by hopscotching to less-restricted areas.
Still, choosing between limited closures and widespread restrictions is "a very, very difficult decision," Althouse notes.
"I'm glad I'm not the one making it."
Early in the outbreak, countries tried to quell hot spots from Wuhan, China - where a stringent lockdown was seen as key in squelching transmission in the world's most populous country - to Italy, where a decision to seal off 10 towns in the northern region of Lombardy evolved within weeks into a country-wide lockdown.
After the virus' first surge, officials fought flare-ups with city-sized closures in recent months in places from Barcelona, Spain, to Melbourne, Australia.
In the English city of Leicester, non-essential shops were shut down and households banned from mixing in late June.
The infection rate fell, dropping from 135 cases per 100,000 to around 25 cases per 100,000 in about two months.
Proponents took that as evidence localised lockdowns work.
Sceptics argued that northern summertime transmission rates were generally low anyway in the United Kingdom, where the official coronavirus death toll of more than 43,000 stands as Europe's highest, according to figures compiled by Johns Hopkins University.
With infection levels and deaths rising anew in Britain, scientists have advised officials to implement a country-wide, two-week lockdown.
Instead, the government carved England into three tiers of coronavirus risk, with restrictions ranging accordingly.
If hot spot measures can be strategic, they also have been criticised as unfairly selective.
In Brooklyn, Orthodox Jews have complained their communities are being singled out for criticism.
In Madrid, residents of working-class areas under mobility restrictions said authorities were stigmatising the poor.
Restaurant and bar owners in Marseille, France, said the city was unfairly targeted last month for the country's toughest virus rules at the time.
As of Saturday, several French cities, including Paris and Marseille, were subject to restrictions including a 9pm curfew.
Australian Associated Press