OAKLAND — County health officials in California say they have no idea whether their Covid-19 cases are rising or falling due to an ongoing state data glitch, making it all but impossible to determine whether they’re making headway in controlling the pandemic.

Santa Clara County Public Health Officer Sara Cody, the Silicon Valley official who coordinated the nation's first regional pandemic lockdown in March, likened the projected underreporting of case counts to the early days of the crisis, when lack of testing blinded the ability of health officers to gauge the spread of the novel virus.

“Right now, we’re back to feeling blind,” Cody said at a press briefing Wednesday. “We don't know how the epidemic is trending. It’s not just inconvenient. This lack of data doesn't allow us to know where the epidemic is heading, how fast it is growing — or not.”

The breakdown appears to have occurred between California laboratories processing coronavirus tests and the state data system, the California Reportable Disease Information Exchange, also known as CalREDIE. California Health and Human Services Secretary Mark Ghaly, the state's top health official, said this week that's where data is getting stuck, but he didn't explain why that happened or when it would be resolved.

Cody indicated Wednesday the glitch may date as far back as the middle of July — right when the state began those closures in dozens of counties in an effort to turn the tide.

California is at a pivotal point in its coronavirus journey, hoping that a mask mandate and closures of gyms, bars and indoor dining may have been enough to stop a summer surge from spiraling out of control. After controlling the virus in the spring, California saw a dramatic spike in cases after it reopened various sectors, moving past New York as the state with the most cases in America — more than half a million.

The data problem was revealed just as California officials started feeling more confident about the state's coronavirus trajectory. On Monday, Gov. Gavin Newsom touted the fact that the seven-day daily average for positive test results had dropped 21 percent compared to one week earlier.

It remains unclear to what extent Newsom's seven-day average drop was due to undercounts versus an actual drop in cases. On Wednesday, a California Department of Public Health spokesperson said the state is “diligently addressing this matter,” but could offer no additional information.

Santa Clara County has offered technical assistance to the state to help fix the problem, which Cody explained appears to be happening between where the electronic lab reports some in and how they are routed. “They’re not getting routed the way they need to be into the CalREDIE system,” she said.

Local health departments on Wednesday reported case counts with caveats warning of incomplete or underreported data due to “delays” or “problems” with the state’s electronic lab reporting system. Hospitalization data, including ICU admissions, are collected in a different way and are not affected by the state’s reporting issue.

Andrew Noymer, an epidemiologist at the University of California, Irvine, suspected something was off when he noticed Orange County on Monday reported more than 17,000 additional tests from a day earlier, while positivity rates — the percentage of people who test positive among all tests processed — had dropped precipitously. “This is way above normal and smells like a data glitch,” he tweeted.

“They need to right this ship. Like ASAP,” Noymer said in an interview. “For 24 hours, we can have a data glitch. For 48, maybe it’s not a big deal. But after 72 hours, it really may be a big deal.”

Not having the proper data prevents local health officers from knowing what’s going on at the city and ZIP Code levels, as well as at individual institutions like nursing homes, Noymer said. “The public health boots-on-the-ground people need to know where to take action,” he said.

Besides guiding local officials in how to use scarce resources to combat the virus, state data controls whether counties and various sectors can resume activity. Case counts are one factor in determining whether counties must remain on the state's watch list, a status that requires closure of everything from school campuses to gyms and churches. Thirty-eight of California's 58 counties, with more than 90 percent of the population combined, are currently subject to watch list closures.

The state's biggest concern of the moment is the Central Valley, a predominantly rural stretch of the state responsible for much of the produce in California and the nation.

In the Valley's hard-hit Kern County, which has reported more than 11,000 new cases over the past two weeks, health officials reported a dramatically low increase of just over 100 new cases Monday and no additional deaths. The county’s Covid-19 dashboard notes the case count over the past few days may not have been reported.

“We’re hopeful this technical issue will be resolved quickly so we can continue our fight to protect our county residents,” said Matt Constantine, director of Kern County Public Health Services Department, in a statement. He said CDPH informed public health departments of the technical issues in an e-mail on Friday.

Despite the glitch, some health experts say they believe the picture in California is actually improving.

California's positivity rate continues to dip — to 6.4 percent, according to numbers reported Wednesday. The state is also reporting modest drops in hospitalizations of 1.9 percent and in ICU admissions of 3.4 percent. Individual counties, including Santa Clara, have also reported declines in hospitalizations.

“As you look through the big contributors to this, they all have very similar trends,” said George Rutherford, a University of California, San Francisco professor of epidemiology and biostatistics, in a webinar Wednesday. “That’s one of the things that I think makes me somewhat more confident that the trends are real.”