A shortage of testing materials has stymied Pennsylvania’s efforts to significantly increase coronavirus testing statewide, a critical tool in slowing the spread of the virus, at the same time that national labs are facing turnaround delays in delivering results, the governor and health secretary said Thursday.

Pennsylvania is averaging more than 22,000 coronavirus test results per day and testing at least 4% of the population each month, said Health Secretary Rachel Levine. But the Health Department’s short-term goal is to test 5% of Pennsylvanians or more per month.

“We need to do better,” Gov. Tom Wolf told reporters, characterizing the state’s testing as “below average.”

Testing, along with contact tracing — the state this week announced plans to hire 1,000 tracers — helps to track the spread of the virus and keep people who have been exposed from unknowingly spreading it. The state’s power to improve its capacity could be a key factor in keeping case numbers tamped down and avoiding another peak before a vaccine is ready.

Noting any event that brings people together “is going to help that virus get us,” Wolf also announced a joint recommendation from the Departments of Health and Education to postpone school and youth sports statewide until at least Jan. 1. It is not a mandate, Wolf’s office said, leaving ultimate decisions up to school administrators. But the Pennsylvania Interscholastic Athletic Association, which had been working to organize fall high school sports, said it was “tremendously disappointed” and would consider its next steps.

Officials reported 807 infections on Thursday, pushing the commonwealth’s seven-day average of new cases down to 788, the lowest since July 14. And Philadelphia reported just more than 100 infections, continuing what has been a daily decrease in new cases this week.

“As case counts go down, contact tracing becomes even more important,” Philadelphia Health Commissioner Thomas Farley said.

Across the United States, more than 4.8 million people had tested positive for the virus as of Thursday and New Jersey reported 411 new cases. And for the 20th week in a row, more than one million Americans filed new unemployment insurance claims.

Nationwide, states have had issues with testing, including supply shortages and data reporting problems, even as they rely on the results to gauge the virus’ ever-changing threat level.

Levine said Pennsylvania is attempting to secure necessary supplies to expand testing in hospitals. The state has also partnered with Walmart, which will offer tests in at least 13 locations throughout the state with appointments made through Quest Diagnostics. But the results from those tests are still subject to delays of up to two weeks due to increased demand from states suffering larger outbreaks.

“Fourteen days … that’s too long,” Levine said. “What we’ve been told by Health and Human Services is they’re working with Quest and LabCorp in their capacity to decrease that wait time.”

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Philadelphia received more than 3,000 test results Thursday, Farley said, and only 3.6% were positive. In recent weeks, that positivity rate had been around 5% or higher, the threshold that officials have said is a warning sign that the virus could be surging.

The decrease in new cases may be attributable to more Philadelphia residents wearing masks and practicing social distancing, Farley said. But he also noted that the city’s recent uptick in cases appeared to have peaked in mid-July, around the same time new cases peaked nationwide.

“So it may be related to the fact that, to a certain extent, this epidemic is a national epidemic and we rise and fall with the nation,” he said.

Farley urged residents to respond if they hear from the city’s team of contact tracers, echoing a plea by other cities and states. New Jersey officials have cited problems with people not wanting to cooperate with tracing efforts, even though contact tracers primarily serve to alert people who need to be tested or quarantined. They don’t have the authority to fine or cite someone who doesn’t properly quarantine or follow other coronavirus safety protocols.

Farley said about one-third of Philadelphians who have been contacted through tracing efforts have not answered the calls, which in the city typically come from phone numbers that begin with the digits “215-218-” and are followed by four more digits that vary.

The city’s recent COVID-19 cases have largely been in young residents; Farley said he is closely watching case counts among older people. It is still possible that a spike could come if younger people spread the virus to older residents, he said.

“I’m concerned [about] what’s going to happen when the weather turns cold and respiratory viruses tend to get worse,” Farley said. “So we’re not out of the woods, even if the case counts continue to fall over the next few weeks.”

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One reminder of that came in Upper Darby on Thursday, where the township announced its entire sanitation department would be quarantined for the next two weeks due to a coronavirus outbreak.

A contingency plan for trash collection until Aug. 24 will be announced Monday, Mayor Barbarann Keffer said in a video statement.

Upper Darby had 220 new cases in July, more than any other suburban municipality or Philadelphia zip code. Delaware County’s new case numbers had been on the rise throughout July, nearly doubling in total over June.

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Also on Thursday, Philadelphia officials announced a plan to provide low-income families with free internet access through wireless hot spots or broadband, a step intended to ensure that all public school students can participate when the district begins the academic year virtually next month.

While other area school districts are also planning to begin the school year virtually, some have proposed bringing students back to classrooms. In the Central Bucks School District, options for students include in-person learning that would space students a minimum of three feet apart.

On Thursday, Pennsylvania’s largest teachers’ union called on the Bucks County Health Department to tighten its school reopening guidelines, saying three feet of social distance in classrooms is not enough to protect against the spread of the coronavirus. The Centers for Disease Control and Prevention has called for schools to aim for spacing students at least six feet apart — a recommendation that has been adopted by Pennsylvania health and education officials.

Rich Askey, president of the Pennsylvania State Education Association, said in a letter to county officials that their guidance to schools “is at odds with virtually every generally understood health guidance.”

“To recommend anything less in school buildings will put students, teachers, support professionals, and their families at unnecessary risk of contracting COVID-19 and increase the likelihood that they will spread the virus to others,” it said.

County officials said the union was mischaracterizing their guidelines, saying they have set three feet as a minimum if six feet isn’t achievable — rather than as a standard to aim for. In recommending schools provide at least three feet of social distance, Bucks’ Health Department has pointed to World Health Organization guidelines.

Contributing to this article were staff writers Maddie Hanna, Phil Anastasia, Kristen A. Graham, and Allison Steele.