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 May 19, 2022

Confirmed COVID-19 Cases

Probable COVID-19 Cases

Total Confirmed and Probable COVID-19 Cases

8,797,890
639,826
9,437,716


COVID-19 Cases by Test Type

As of May 19, 2022

MonthNo. ConfirmedNo. ProbableTotal COVID-19 Cases (Confirmed and Probable)% Confirmed% Probable
​May 2022
​153,957
​19,323
​173,280
​88.8
​11.2
​April 2022
​127,753
​13,139
​140,892
​90.7
​9.3
March 2022
77,627
8,686
86,313
89.9
10.1
February 2022316,449
38,017
354,466
89.3
10.7
January 20222,541,754
249,994
2,791,748
91
9
December 2021720,705
55,221
775,926
92.97.1
November 2021152,057
13,110
165,167
92.17.9
October 2021163,692
15,923
179,615
91.1
8.9
September 2021231,453
20,717
252,170
91.8
8.2
August 2021387,066
27,871
414,937
93.36.7
July 2021189,756
13,977
203,733
93.1
6.9
June 202132,921
2,827
35,748
92.17.9
May 202134,949
3,365
38,314
91.28.8
April 202160,337
5,783
66,120
91.3
8.7
March 202176,703
6,840
83,543
91.88.2
February 2021170,650
11,996
182,646
93.4
6.6
January 2021834,909
44,324
879,233
95
5
December 20201,164,095
59,136
1,223,231
95.24.8
November 2020400,026
17,554
417,580
95.84.2
October 2020120,620
4,230
124,850
96.63.4
September 202098,795
2,489
101,284
97.52.5
August 2020149,133
2,671
151,804
98.21.8
July 2020280,814
1,921
282,735
99.30.7
June 2020173,897
334
174,231
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.