The state posted this disclaimer on its COVID dashboard.

Health officials in multiple California counties say the electronic system used by most local health departments statewide to report data on infectious diseases is currently experiencing “serious” technical issues, resulting in coronavirus cases being significantly undercounted.

The technical problems suggest that the apparent statewide decline in COVID-19 activity that had been observed in the past few days, and which Gov. Gavin Newsom touted Monday as an indication the state has been “able to get a handle” on the pandemic, may instead be either partially or entirely attributed to a data glitch.

The California Department of Public Health confirmed the undercounting in an update to its dashboard after individual counties, including in the Sacramento area and Southern California, reported earlier in the week that they’d been made aware of the problem.

“Due to issues with the state’s electronic laboratory reporting system, these data represent an underreporting of actual positive cases in one single-day,” the note attached to the CDPH graph on daily lab-confirmed case increases reads.

Monday’s statewide data update saw just 5,739 new cases reported, and Tuesday’s was even lower at just over 4,500 new cases. Those numbers would represent the two lowest single-day increases since July 5, as well as a relatively abrupt turnaround for numbers that had been spiking steadily since mid-June. California has surpassed 519,000 total lab-confirmed cases, even with the undercount. The state also reported 113 new fatalities Tuesday, bringing the state’s all-time COVID-19 death toll to 9,501.

The state did not say how many days’ data have been affected by this issue, nor did it estimate the scale of the undercounting. But individual county health officials have suggested that the underreporting has noticeably affected the accuracy of their own available data in recent days.

The electronic system in question -- the California Reportable Disease Information Exchange (CalREDIE) -- is used by nearly all of California’s local health offices to track disease data and transmit it between those local offices, laboratories, health providers and the state, according to the CDPH website.

Sacramento and Placer counties added disclaimers to their COVID-19 data dashboards, with Placer doing so Monday and Sacramento adding the warning Tuesday morning, amid a few days of reporting comparatively low numbers for new cases.

Placer’s warning statement atop its data dashboard advises: “Please note that CalREDIE, the statewide electronic disease reporting system, is experiencing serious unresolved processing delays. As such, new cases presented here are likely an underestimate of true incident cases being reported. This impacts many of our statistics, including case rates and percent increase estimates.”

Sacramento County health officials wrote: “The state’s electronic disease reporting system has been experiencing issues processing incoming reports. Therefore, recent data published on the Sacramento County Public Health COVID-19 dashboards are likely to be an underestimate of true cases in the county.”

The disclaimers came after both counties had reported significantly fewer new case totals in recent days than they did throughout most of last month. Placer reported 13 new cases each of Sunday and Monday, and Sacramento County increased its tally by a little more than 50 each of Sunday, Monday and Tuesday. For each county, daily new case counts had routinely been triple those figures or more for much of July.

The state health department acknowledged the issue to The Sacramento Bee on Tuesday and says it is working with local health offices to fix the problem.

“The California Department of Public Health has been proactively working with data submitters, including laboratories and local public health departments, to address data reporting delays,” California Health and Human Services spokeswoman Kate Folmar told The Bee via email Monday.

Sacramento County’s health chief, Dr. Peter Beilenson, told The Bee on Tuesday that the state says it will try to send more accurate data to the county in a spreadsheet format, and that CDPH provided no time frame for the CalREDIE problem being fixed.

Riverside’s public health director, Dr. Kim Saruwatari, said Monday in a statement that CDPH informed the county of the issue late last week via email and confirmed to the local health office Monday that it had “urgently escalated this issue to leadership.”

The CalREDIE reporting issue does not appear to be affecting data on hospitalizations or death figures at the state or county levels.

“(T)he scale and scope of data being collected in response to COVID-19 is unprecedented,” Folmar wrote. “This has required the state to expand the capacity and capabilities of our systems.”

Folmar also confirmed hospitalization and ICU admissions are “collected through a separate system, not CalREDIE.”