LOS ANGELES (CNS) - Los Angeles County has reported a record number of new coronavirus cases, topping the 4,000 mark for the first time since the pandemic began, although about half of the cases were attributed to a backlog of results from a single lab dating back to Thursday last week.

More concerning, however, was the continued rise in the rate of people testing positive for the virus. Although the cumulative rate of positive tests throughout the pandemic remains at 9 percent, the average over the past seven days rose to 11.6 percent, according to the county Department of Public Health. That seven-day average rate is up from 10 percent on Monday, and up from about 8.4 percent last week.

The number of people hospitalized rose to 1,969 on Tuesday, nearing peak-pandemic levels. On Monday, there were 1,921 people hospitalized. Three weeks ago, the hospitalization number was averaging between 1,350 and 1,450, according to the county. The hospitalization figures do not include Pasadena and Long Beach, which each have their own health departments.

Overall, the county reported 4,015 new cases, but it attributed about 2,000 of them to a backlog of test results from a single lab, representing tests between Thursday and Sunday. Long Beach reported an additional 218 cases Tuesday, while Pasadena added seven.

The new cases lifted the overall county total of confirmed cases throughout the pandemic to 120,764.

The county also reported 46 new deaths from the virus, although three of those fatalities were reported Monday by Long Beach and Pasadena. Long Beach reported an additional three deaths Tuesday.

The countywide death toll from the virus stood at 3,582 as of Tuesday afternoon.

County health officials said Monday that about half of the new cases being confirmed are now occurring among people between 18 and 40 years old, marking a notable shift in infections. Younger residents are also seeing increasing hospitalization numbers, as are people aged 41-64. People aged 65 and older had represented the majority of hospitalizations through most of the pandemic, but those numbers have dropped in recent weeks, county officials said.

Health officials have said the numbers are indicative of increasing community spread of the virus, with younger residents more likely to be out and about as businesses reopened -- most notably bars and restaurants. Younger residents were also more likely to have taken part in mass protests against police brutality over the past month.

The spread is also likely the result of people ignoring mandates for social distancing and wearing face coverings when mingling with people outside their own households.

County public health director Barbara Ferrer on Monday cited USC research that found the percentage of people who stay home and leave only for essential reasons has dropped dramatically from 86 percent in April to about 58 percent now.

And with more businesses reopened, Ferrer noted that 43 percent of residents have a job that requires close contact with other people on a daily basis.

"It's clear that after months of quarantine, combined with the reopening of many sectors in the span of several weeks, we've had a lot of people disregard the very practices that allowed us to slow the spread," Ferrer said. "And unfortunately, this cannot continue. Our inability to follow the most basic infection-control and distancing directives leads to serious illness and even the deaths of people we love and the deaths of those who are loved by others. And the evidence is overwhelmingly clear about the impact.

"It requires us, if we do not find it in ourselves to actually continue to adhere to the social-distancing and infection-control practices, it finds us in a place where we're slowing down our recovery journey. What we do now will determine where we are in three to four weeks."

County officials warned last week that unless the trend of increasing case numbers and hospitalizations reverses, local hospitals could be in danger of being overwhelmed. But the county's medical services director, Dr. Christina Ghaly, said the rate of hospitalization increases has slowed somewhat over the past week. Updated hospital projections are expected to be released later this week.