Recommending continued vigilance they said will help spare the region from a new surge in coronavirus cases, Philadelphia and Delaware County officials on Thursday urged residents to call authorities when they see restaurants or bars allowing patrons to enter without masks or congregate at unsafe distances.

Their appeals come as coronavirus cases rise among young people and people who visited crowded bars in the Philadelphia and Pittsburgh regions, New Jersey, and other states. People 19 to 24 now account for 17% of the Philadelphia region’s coronavirus cases since the pandemic started, up from 5% in April and 15% in June, according to the state Department of Health.

“A crowded bar … is one of the most dangerous places to be in the United States right now,” Delaware County Council member Elaine Schaefer said at an afternoon news conference in Media. “If you show up in an establishment and you see that there’s no way you can go in there and social distance, and that there’s nobody wearing a mask, don’t go in. Just don’t do it.”

Philadelphia shut down two restaurants over the weekend. The state issued citations to two establishments in Delaware County for flouting the state’s public health rules in the green phase of reopening, officials there said, and the State Police inspected more than 2,000 bars statewide last weekend.

The Delaware County Council said local law enforcement officers and officials would be strictly enforcing protocols in establishments with liquor licenses. The majority of businesses are following the rules and are concerned about bad actors jeopardizing their livelihoods, said Vice Chair Monica Taylor.

All Pennsylvanians can report bars and restaurants that are not enforcing six-foot social distances or mask-wearing to the state police through the liquor code violation website or hotline. Anyone who suspects a restaurant in Philadelphia is not following safety protocols can call 311 to complain, and the city will send an inspector to investigate, Philadelphia Health Commissioner Thomas Farley said Thursday.

Though they are less likely to die from the virus, younger people are more likely to be asymptomatic and pass the virus to older people, who are more likely to die, Farley noted. To avoid the increasing death rates occurring in other states — which lagged behind increased case counts — wearing masks is key, Farley said.

The spread of the virus indoors has been of particular concern to health officials as states that reopened earlier have seen surges of the sickness. The World Health Organization on Thursday for the first time said airborne transmission of the virus “cannot be ruled out,” meaning that the virus could hang in the air and cause infection.

The virus is primarily transmitted when an infected person releases respiratory droplets by talking, coughing, or sneezing; face masks are effective in trapping the droplets. However, airborne spread would mean the virus could linger in the air and float beyond six feet in poorly ventilated places such as restaurants, nightclubs, places of worship, or office buildings.

The WHO’s updated scientific brief stressed that evidence is inconclusive and airborne transmission has not been proven. Still, the organization recommended that people avoid crowded indoor gatherings.

Three out of four Philadelphians surveyed said they believed everyone in the city should be wearing face masks whenever they leave the house, but one-quarter of residents are uncertain about or opposed to wearing masks, Mayor Jim Kenney said Thursday, as he unveiled a $750,000 marketing campaign to promote mask-wearing.

“Mask use is critical to continuing to reopen and resume a sense of normalcy in our lives,” Kenney said.

Still, the city does not plan to fine people who ignore the mandatory order to wear a mask in public. Kenney said enforcement was “difficult” and he hoped the ad campaign — which will feature the slogans “Philly never backs down. Mask up” and “Love your neighbor. Wear a mask” in different languages — would “drive home” the importance of the measure.

In June, the city found that about 55% of people at SEPTA stations and 78% exiting retail stores in Philadelphia were wearing masks, Farley said.

“It’s not 100%, and to avoid a second wave, we need to do better than that,” the health commissioner said. “We need to make masks the new normal.”

Farley reported 159 new coronavirus cases in the city and two deaths on Thursday. The average for the last week has been about 115 new cases per day, but the trend “does change a lot from day to day,” Farley said. The percentage of people tested who were positive hovered around 5% to 6% over the last couple of weeks.

Gov. Tom Wolf on Thursday extended the state’s moratorium on home evictions and foreclosures to Aug. 31. The new executive order applies to homeowners or tenants who have not received assistance from the Pennsylvania Housing Finance Agency or are not receiving relief through one of several federal programs or judicial orders.

“I am taking this action to help families know they will have a roof over their heads and a place to live while all of us fight the COVID-19 pandemic,” Wolf said in a statement.

Philadelphia already has its own moratorium on evictions and foreclosures through at least Aug. 31. Landlords in Philadelphia are suing the city in an attempt to overturn new coronavirus pandemic renter protections.

Pennsylvania reported 719 new coronavirus cases Thursday. The seven-day average of new cases decreased slightly but has remained above 500 for 15 straight days.

The state announced a new fund of $10 million to support grocery stores, corner stores, farmers markets, and other food retailing businesses and nonprofits serving customers in low-to-moderate-income areas. Eligible businesses can apply on the Department of Agriculture’s website.

New Jersey, which reported 354 new coronavirus cases Thursday, also announced federal funding for local food banks: $10 million in CARES Act funding will be distributed to state food banks by August, and another $10 million between August and December, Gov. Phil Murphy said.

“The number of families facing food insecurity has grown, unfortunately, because of the impacts of COVID-19,” Murphy said, speaking at a food bank in Union County.

The Department of Human Services also began delivering $208 million in special food assistance benefits Thursday to more than 500,000 schoolchildren who would have received free or reduced-price school meals, Murphy said. That amounts to a onetime benefit of $416 per child. New Jersey is sending the aid directly to all eligible families; people do not have to apply for the assistance.

Pennsylvania’s governor asked residents to remember to wear masks when outdoors with others, including when visiting state parks and when at swimming pools. In the water, swimmers should not wear masks but should social distance.

Philadelphia spraygrounds were turned on last week, and by Thursday, another piece of summer was returning to the city.

Basketball hoops, most of which had been removed at the start of the pandemic, were being reinstalled at Philadelphia neighborhood playgrounds.

For the first time in months, and despite sweltering heat, people went onto courts to shoot baskets.

Staff writer Marie McCullough, staff photographer Alejandro Alvarez, and graphics editor John Duchneskie contributed to this article.