1  Course of the Outbreak

Please hang tight. The application below may take a minute or two to load.

Statewide Infections by Month

May 2023 - Dec 2023

  • For each metric, cell shading reflects the relative contribution of each month to the total across all months combined.

  • Darker shading = months with higher infection counts or rates relative to other months

  • Infection and Severe Infection rates are reported as the number of cases per 100,000 population

Timeline of the Outbreak

May 2023 - December 2023

May 28, 2023:

Cumulative Infections: 13,875

June:

Cumulative Infections: 133,835

Infections increased rapidly, with weekly new cases rising 50 to 100 percent compared with the previous week. This was the most intense growth phase of the outbreak. By July 8th, we saw a 864.58% increase since May.

July:

Cumulative Infections: 441,588

The outbreak began to slow in terms of it’s week-over percent growth, dropping to about 20 to 30 percent, but the number of new infections reported each week continued to rise. By the end of July, there was a 229.95% increase.

September-October:

Cumulative Infections: 4,185,531

We saw the largest growth in cumulative infections statewide during September and October, with an average of over 334,000 new cases reported each week.

November:

Cumulative Infections: 4,533,887

Growth in weekly percent change in new cases drops precipitously to less than 1%, and we start to see the outbreak slow down.

December 30:

Cumulative Infections: 4,549,583

New infections have continued to decline each week, but we are still getting reports of new cases.

Most importantly is that there is now a much higher proportion of new infections that are severe and require hospitalization.

While the State of California is seeing dramatically fewer infections overall, seeing a higher proportion of infections that are severe requires our continued vigilance and dedication to address this outbreak as a community: maintaining clinical capacity, strengthening rapid detection, and ensuring that the communities being hit the hardest get the resources they need.