Boston's positive coronavirus testing rate spiked to 2.8% for the week ending Sept. 12, Mayor Marty Walsh said at his regular update on the pandemic Thursday.
The rate was at 1.5% the week before. The near-doubling could be due to a dramatic decline in testing, according to the mayor -- residents had been taking an average of about 3,000 tests per day but it dropped to 1,800 tests per day over Labor Day weekend.
"We're going to monitor that very closely. Any increase that we're seeing in numbers is concerning," Walsh said, noting that the rate may tick back down after the period covered by the holiday weekend.
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Walsh also reported that nearly half of cases in the last two weeks have been in people under 30 years old, and that five neighborhoods are now seeing higher testing rates of between 4 and 5%: Allston-Brighton, Dorchester, Hyde Park, Roslindale and West Roxbury.
The city is looking at ways to dedicate new resources to those neighborhoods, including through mobile testing sites -- East Boston, which has had mobile testing, has dropped its positive rate from a high of 11.4% to 5.2%, which Walsh deemed "incredible progress."
Among all COVID cases in Boston, 48% have been in young people in the last two weeks, according to Walsh, who urged them to consider how getting the virus can impact their loved ones and to refrain from holding parties or engage in other risky behavior.
"I understand that young people will be active and social but we're also need you to be conscious and careful," the mayor said.
The city's chief of Health and Human Services, Marty Martinez, said younger people in Boston testing positive for the virus "has been a trend that we've seen post-the peak of the coronavirus."
He said officials haven't seen any specific clusters, and suggested it was down to young people thinking the serious impact of COVID-19 is on older people.
"That doesn't mean the people around them won't have a severe impact," Martinez cautioned.
Walsh reported a total of 16,430 cases of COVID-19 in the city through Thursday, including 759 deaths.
The remarks come after Walsh on Tuesday announced the city would extend the outdoor dining season to help restaurants amid the pandemic.
The outdoor dining season was initially supposed to end Oct. 31, but restaurants will be able to keep tables on sidewalks and behind barriers in parking spots until at least Dec. 1. If their outdoor seats are on private property, they can stay indefinitely, until the end of the public health emergency Walsh declared because of the pandemic.
Boston has helped restaurants put up barriers and ramps, but beyond waiving fees for permits to use heaters, establishments won’t be getting any assistance to buy equipment to keep diners warm.
The city will also install new bus lanes on Columbus Avenue in Egleston/Jackson Square, North Washington Street in the North and West ends and Washington Street in Roslindale, all places "where working people rely on MBTA buses very heavily," Walsh said.
And many pop-up bike lanes created in downtown Boston will be made permanent, the mayor said, asking for patience as construction workers make the changes.
Walsh on Tuesday also welcomed City Councilor at Large Michelle Wu to run for his office, commending her for the decision she announced hours earlier.
"I have great respect for her and everyone who runs for office," Walsh said during his regular coronavirus update outside City Hall.
“We won’t have enough money, I think, to be able to build infrastructure around these facilities," Walsh said, adding, "we’re going to try to continue to be creative as we move forward.“
Restaurants will also have to continue to abide by safety regulations.