California’s new case rate seems to have peaked and might even be going down, but recent problems with under-reporting in the state’s data and surveillance system has raised questions about those numbers.

Average new cases have started to decrease over the past two weeks, after remaining relatively flat since July 10. To see where the virus is spreading, we calculated the rate of new cases in each county, the number of cases reported in the previous 14 days per 10,000 residents, then mapped that data over time. The animated map shows how — and when — the coronavirus spread around California from April 1 through August 6.

In early April, the virus was most prevalent in Bay Area and Southern California counties, then became more concentrated in Los Angeles and Imperial counties toward the end of the month, spurred by widespread community transmission. In May, the virus spread farther into the state, as large outbreaks at prisons caused spikes in Santa Barbara and Kings County.

In June the virus took a stronger hold in many parts of Southern California and the Central Valley. It continued to spread quickly from late June through the middle of July when it flattened. New cases started to decrease in late July and early August.

On April 1, only 12 counties had a rate of more than 2.5 cases per 10,000 residents in the previous 14 days. On June 1, 26 counties had an elevated new case rate and by July 9 nearly all counties, 53 of 58, had a new case rate over 2.5. Two weeks later on July 23, only 3 counties had a case rate under the 2.5 threshold. And on August 6, only two counties had cases below the 2.5 threshold.

The map shows California’s early stay-at-home order likely spared the state from the early exponential growth seen in places like Italy and New York. But while the Golden State kept the curve under control for many weeks in the beginning, the trend lines got worse through June and early July. Now the number appears to be decreasing, but until the state resolves its data problems we do not really know if we have turned the corner.

Find more data on coronavirus cases, hospitalizations and deaths in the Bay Area and elsewhere in California with our Coronavirus Tracker