Probable-Cases Tracking Confirmed and Probable COVID-19 Cases

Tracking Confirmed and Probable COVID-19 Cases

CDPH tracks both probable and confirmed cases of COVID-19 to better understand how the virus is impacting our communities. Probable cases are defined as individuals with a positive antigen test that detects the presence of viral antigens. Antigen testing is useful when rapid results are needed, or in settings where laboratory resources may be limited. Confirmed cases are defined as individuals with a positive molecular test, which tests for viral genetic material, such as a PCR or polymerase chain reaction test. Results from both types of tests are reported to CDPH.

Due to the expanded use of antigen testing, surveillance of probable cases is increasingly important. The proportion of probable cases among the total cases in California has increased.  To provide a more complete picture of trends in case volume, it is now more important to provide probable case data in addition to confirmed case data. The Centers for Disease Control and Prevention (CDC) has begun publishing probable case data for states. 

Antigen Tests

Antigen tests are reliable, but somewhat more prone to false positive or false negative results. Thus, persons with a positive antigen test result are classified as probable cases based on national case definitions.  Many antigen tests are not required to be performed in a laboratory which allows for a much quicker result.

Molecular (PCR) Tests

Molecular tests for COVID-19 include polymerase chain reaction (PCR) and other types of nucleic acid amplification test (NAAT) tests. Molecular tests are generally more sensitive and specific because they are detecting direct genetic material.  Most of these tests must be processed in a laboratory, which requires waiting a day or more until results are known.

Cases that have both positive antigen test results and positive molecular test results are considered confirmed cases, and only counted once as a confirmed case.

For more information see: CDPH Factsheet for PCR, Antigen and Serology Testing   


COVID-19 Cases in California: Confirmed and Probable 

As of September 15, 2022

Confirmed COVID-19 Cases

Probable COVID-19 Cases

Total Confirmed and Probable COVID-19 Cases

10,354,899
829,755
11,184,654


COVID-19 Cases by Test Type

As of September 15, 2022

MonthNo. ConfirmedNo. ProbableTotal COVID-19 Cases (Confirmed and Probable)% Confirmed% Probable
​September 2022
​46,166
​5,681
​51,847
​89.0
​11.0
​August 2022
​291,933
​44,684
​336,617
​86.7
​13.3
​July 2022
​517,306
​68,687
585,993
​88.3
​11.7
June 2022
477,652
54,373
532,025
89.8
10.2
May 2022371,325
43,665
414,990
89.5
10.5
April 2022128,768
13,234
142,002
90.7
9.3
March 202277,522
8,288
85,810
90.3
9.7
February 2022315,800
37,146
352,946
89.5
10.5
January 20222,546,435
247,548
2,793,983
91.1
8.9
December 2021722,304
54,715
777,019
93.0
7.0
November 2021151,860
12,985
164,845
92.17.9
October 2021163,348
15,712
179,060
91.2
8.8
September 2021231,215
20,496
251,711
91.9
8.1
August 2021387,114
27,571
414,685
93.4
6.6
July 2021189,912
13,823
203,735
93.2
6.8
June 202132,979
2,804
35,783
92.2
7.8
May 202134,991
3,304
38,295
91.4
8.6
April 202160,365
5,699
66,064
91.4
8.6
March 202176,727
6,729
83,456
91.9
8.1
February 2021170,669
11,797
182,466
93.5
6.5
January 2021833,950
43,503
877,453
95.0
5.0
December 20201,165,238
58,128
1,223,366
95.24.8
November 2020400,046
17,290
417,336
95.9
4.1
October 2020120,590
4,182
124,772
96.63.4
September 202098,767
2,461
101,228
97.6
2.4
August 2020149,201
2,634
151,835
98.3
1.7
July 2020280,851
1,890
282,741
99.30.7
June 2020173,940
331
174,271
99.80.2

*Testing data is updated weekly. Due to small numbers, the percentage of probable cases in the first two weeks of the month may change.