Volunteers who set out across the city Wednesday bearing snacks, toiletries, and socks had prepared for a long night. The annual effort to find and survey every homeless person in Philadelphia typically runs into the wee hours.

But those assigned to the Kensington community knew they would be at it longer than anyone else. Much of the city’s homeless population now lives in the neighborhood at the heart of the nation’s worst big-city opioid crisis.

First in a misty chill, then in an early-morning downpour, they drove the avenues and walked through playgrounds and back alleys, looking for people whose addictions left them in the streets.

The annual count is how the U.S. Department of Housing and Urban Development determines how much it will give the city for various outreach programs, and it helps the city see where to direct its efforts to get people into shelters and even apartments. But in Kensington especially, it has also become a measure of how opioids have gripped the community.

A city count in July found 703 people were sleeping on the streets on a given night in the neighborhood, more than double the previous year’s summer count. In fact, more than half of the city’s homeless were in Kensington, and were in addiction.

Wednesday night’s count won’t be released until it is added to counts of people sleeping in emergency and temporary shelters. Still, officials were cautiously optimistic that it would be lower than last year’s count of 1,020 people experiencing homelessness citywide.

“The general impression, with no data, was that people felt that the numbers were lower [this year],” said Liz Hersh, the head of the city’s Office of Homeless Services.

Whatever the tally, Wednesday’s exercise confirmed something long suspected: Even as three major Kensington encampments of homeless drug users have been cleared -- and many residents sent to treatment or shelters -- some have scattered through the neighborhood, not to find housing, and other people in addiction, new to living rough, have joined them.

On Thursday, the city will clear the fourth and final large encampment, at Emerald Street, where dozens of people have been sleeping for years.

It’s also where many people evicted during the previous three clearings have moved, after declining a shelter bed or other services from the city. (Every resident of the camps has been guaranteed a bed in a low-barrier respite shelter that doesn’t require sobriety to enter.)

Tim Sheahan, director of homeless services for the city’s Department of Behavioral Health and Intellectual disAbility Services, has led teams into the camp every day, offering treatment, wound care and other services, to prepare for Thursday’s eviction. He said he counted 85 people sleeping in 34 tents on Emerald Street Wednesday night.

“Our outreach data indicate that the primary drug of choice [for the homeless population] across the city is still alcohol. But when you look in Kensington, it’s 95 percent opioids. It’s brought in a younger population, a newly homeless population, a highly transient population,” Sheahan said. “A lot of the folks we see, we only see one time.”

That’s because some of the people Sheahan’s team sees do have somewhere to stay. But they flock to Kensington not only to buy drugs, but also for the relative security of using around others. Now that virtually all of the heroin supply is tainted with far more powerful fentanyl, many users carry the reversal drug Narcan to revive others who overdose.

The distinction may not mean much to permanent residents of the neighborhood dealing with open drug use and drug sales. But it’s information the city needs to best serve homeless residents. (Sheahan said that his team offers addiction services to both the homeless and people who have homes but are in Kensington to buy and use drugs.)

Hersh agreed that she couldn’t be sure that all of the 703 people counted in the neighborhood last summer were actually homeless. By now, though, outreach workers are familiar with the population.

“What was really clear [Wednesday] night was that because of all the work we’ve been doing ... they were really able to distinguish between the truly homeless and people who were out there for other reasons,” she said.

That’s what Silvana Mazzella and her team of outreach workers tried to do during last week’s count, patrolling the blocks north of Allegheny Avenue, where the El station on Kensington Avenue is now the scene of newer encampments. By day, Mazzella is the associate executive director of Prevention Point, the city’s only needle exchange. Wednesday night, she recognized several clients -- and recruited several new ones.

“We will look out for you -- come by and ask for help,” she told a man she met behind a Dunkin' Donuts. On another block, a man waved at her from his apartment window. He was a Prevention Point client who now has a home.

Evan Figueroa-Vargas, a volunteer and social-work student, drove Mazzella and a few others down the narrow streets. He grew up in the neighborhood and lost a brother to an overdose. Then, after a motorcycle accident, he got prescription painkillers that started him on a years-long heroin addiction. He paused during the count and looked down the street.

“A little over 20 years ago,” he said matter-of-factly, “I was shot at that stop sign.”

He parked the van at the El stop, where the crew surveyed 25 people in under half an hour. They told the outreach workers familiar stories of addiction, of coming to Kensington, of getting stuck. A man named Ricky said he’d come up from Baltimore in August after hearing of Philadelphia’s cheap, pure heroin, and “got into a world of trouble.” A young man from New Jersey named Shaun marveled at how a week in Kensington had turned into months and then a year.

A woman named Kay told outreach workers she’d spent a year on the streets, enduring bitterly cold nights. She wanted to be indoors, and said she wished the city would do more to help people outside Kensington’s major encampments. But she was afraid, still, to enter treatment: “I would fear to face reality,” she said. “My parents are dead -- I have a fear of having no one to call when I have the urge [to use]."

By 4 a.m., the volunteers were headed back with their tally sheets and completed surveys. “The count is not an exact science,” said David Holloman, the chief of staff at the Office of Homeless Services, who rode with one of the Kensington teams. “But it helps us understand what we need to focus our resources on.”

The subjects of the count said it was encouraging for them as well: “It means a lot. It means I’m not forgotten,” said Ricky. “It means ‘Hey, Rick, you have a chance.’ ”

Editor’s Note: An earlier version of this story listed the incorrect title for Tim Sheahan. He is director of homeless services for the city’s Department of Behavioral Health and Intellectual disAbility Services.