Northern Virginia began the week with its average daily novel coronavirus caseload hovering at the lowest point in more than three months. Elsewhere in the state, that number has reached a record high.

Virginia’s D.C. suburbs reported 161 new cases Monday as the region’s seven-day average stood at 151 daily cases. Northern Virginia’s daily average is similar to where it stood on April 10 before a case surge through the end of May.

The rest of the state outside the Washington region reported 811 new cases Monday, sending its daily average to 640. Excluding Northern Virginia, the state’s average daily caseload has increased seven consecutive days, with four days of record highs.

As Virginia’s trend lines diverge, state health officials are monitoring a continued spike in cases in the Hampton Roads region, where Virginia Beach and nearby localities reported their highest daily numbers Monday since the start of the pandemic. That region is emerging as a trouble spot while leaders in Virginia, Maryland and the District try to keep a lid on caseloads, which have surged across the country.

Virginia Beach, the state’s most populous city, reported an additional 157 cases and the state’s only two deaths on Monday, while its average daily caseload has more than doubled in the past week. Cases in the city for those 29 and younger are up about 250 percent since the last week of May.

Virginia Gov. Ralph Northam (D) has said that the “concerning increase” in the Hampton Roads area could prompt additional restrictions. Health experts are urging the public to follow guidelines such as wearing masks, maintaining social distancing and frequent hand-washing to help stem the spread of the virus.

Virus cases had been decreasing until about mid-June in the greater Washington region, but “that has leveled off,” said Luisa Franzini, a professor and chair of the Department of Health Policy and Management at the University of Maryland School of Public Health in College Park.

“Now we’re starting to see an increase,” Franzini said. “People are out and about, and the virus spreads more easily that way.”

The District, Maryland and Virginia reported 1,449 new cases and eight additional deaths on Monday, bringing the regional caseload to 156,075, with more than 5,800 deaths since the start of the pandemic. During the past four days, the three jurisdictions combined have recorded their biggest daily case numbers since early June.

Maryland reported 418 new ­cases and six deaths Monday. The state’s seven-day average has increased to its highest level since June 15.

At the same time, Maryland’s average number of deaths and other key metrics have held steady or ticked downward, with intensive care unit bed usage at the lowest level since March 29.

Prince George’s County Health Officer Ernest L. Carter announced Monday that the county will proactively test all its public safety workers for the virus. He said the step is being taken to curb asymptomatic spread as the county gradually reopens.

“It is important to know the status of our public safety employees so we can do all we can to ensure that they are not exposing the public to the virus and to ensure that we can continue to maintain continuity of operations of our government,” he said in a statement. “At this time, we have sufficient testing capacity to undertake these efforts.”

Prince George’s leads Maryland in coronavirus infections, reporting 19,773 cases as of Monday.

The District’s caseload also has started to rise in recent days, with its seven-day average the highest in nearly a month. The District reported 59 new cases and no deaths Monday — the city’s fourth consecutive day without a fatality.

The four-day stretch is the longest the city has gone without a virus-related death since its first such fatality, but Health Director LaQuandra Nesbitt warned that an increase is likely in weeks ahead.

“We are aware that we always see an increase in new cases followed by an increase in hospitalizations, followed by an increase in deaths,” Nesbitt said, predicting a lag of about two weeks before new cases result in hospitalizations.

Christopher Geldart, director of the city’s Department of Public Works, said the District is paying $90 per test to have about 1,500 tests per day processed by private laboratories. (The Centers for Disease Control and Prevention and the Federal Emergency Management Agency reimburse the District for much of the cost.)

The city processes the rest of the tests, about 500 daily, at its public health laboratory, where it pays about $50 for the necessary reagents as well as the cost of employees’ time.

Earlier in the pandemic, residents were getting results in three to five days. It is now taking longer as private labs are busier, with more tests conducted elsewhere in the country, Geldart said. He called the turnaround time of five days or more “longer than we’d like.”

As businesses reopen in the region, test positivity rates are a key measurement that experts are watching. That rate has generally held steady in recent days after significant declines started to plateau.

Taison Bell, an assistant professor of medicine in the divisions of infectious diseases and international health and pulmonary and critical-care medicine at the University of Virginia in Charlottesville, said regions of the country with the highest mask use are seeing some of the lowest positivity rates.

“We can’t stay locked in place until a vaccine is available,” Bell said. “The key is making sure people are adhering to public health guidelines.”

Franzini urged leaders to halt the lifting of other restrictions.

“It was fine to reopen some,” she said. “Cases were down, and they’re still overall fairly low compared to what they were. Community spread is limited. But we need a second look as cases are increasing slightly.”

Part of the reason cases are rising, Franzini said, is that more people are traveling.

“They’re increasing the risk of the place they’re traveling to, plus the risk when they’re coming home and bringing it to their own community,” she said.

She noted that despite the rise in cases, the region has enough hospital and ICU beds to handle the illness.

Rachel Chason contributed to this report.