Division of Communicable Disease Control

Tracking Variants

As of April 3, 2025, new COVID-19 sequencing data are currently unavailable and variant reporting will be paused until further notice.

Related Material

CalCAT: Variant Proportion Nowcasts

Variants Are a Normal Part of Viruses

Viruses change through mutations that create new strains of virus over time. This is a normal process that happens with most viruses. We call these strains variants.

Some variants grow and persist in the community while many variants simply fizzle out. Most variants do not have a meaningful impact on things like hospitalization rates, severity, or infectivity.

Why Are We Tracking Variants?

Scientists and public health officials are studying variants to learn more about how to control their spread. They want to understand whether the variants:

Change the effectiveness of COVID-19 vaccines
Cause milder or more severe disease in people
Spread more easily from person-to-person
Are detected by currently available viral tests
Respond to medicines currently being used to treat people for COVID-19

Variants We Are Tracking

Variants of Concern

Variants of concern are likely to have one or more of the following features:

More contagious
Likely to cause more severe symptoms
Resistant to treatment
More resistant to vaccines

Variant	Known differences
Delta	200% increased transmission compared to other variants Reduced antibody treatment effectiveness
Omicron	At least 2 to 4 times more transmissible than the Delta variant Reduced effectiveness of certain antibody treatments

Variant

Known differences

Delta

200% increased transmission compared to other variants
Reduced antibody treatment effectiveness

Omicron

At least 2 to 4 times more transmissible than the Delta variant

Reduced effectiveness of certain antibody treatments

Mutations are very commonly found in the Spike protein, which facilitates the virus entering the cell. The Spike protein is also the target of many vaccines, and mutations in this protein are associated with increased immune evasion.

Genomic Surveillance

The State of California alongside various public and private partners select positive COVID-19 tests for whole genome sequencing to understand what variants are circulating in the community. Sequencing allows scientists to look at the unique genetic code of a virus which can be used to compare similarities and differences between samples.

Current Variant Proportions and Modeling Estimates

Percent prevalence of variants circulating in California are listed in the table below. Of total cases sequenced in February 2025, 33.1% were XEC, a recombinant of KS.1.1 (JN.1.13.1.1.1) and KP.3.3 (JN.1.11.1.3.3), 23.7% were KP.3.1.1 (JN.1.11.1.3.1.1) , and 22.7% were LP.8.1 (KP.1.1.3.8.1). LA testing data are available for dates up to 3/11/25. For dates 3/11/25 and beyond, LA data are not included in case metrics, as they are currently unavailable.

Lineage	KP.1.1	LP.8.1	KP.3	KP.3.1.1	MC.1	MC.10.1	LF.7	XEC
Parent	JN.1.11.1	KP.1.1	JN.1.11.1	JN.1.11.1	KP.3.1.1	KP.3.1.1	JN.1.16	JN.1.13 x KP.3
Dec 2024	2.3%	9.2%	3.4%	27.4%	6.5%	2.2%	2.2%	34.0%
Jan 2025	0.7%	13.0%	2.2%	15.3%	5.2%	9.7%	3.8%	35.3%
Feb 2025	2.2%	22.7%	1.7%	9.4%	4.4%	9.9%	5.5%	33.1%

Since there is a known delay in the availability of sequencing results, CDPH CalCAT model provides estimates of variant proportions for the most recent weeks. Models are updated biweekly on Fridays. Based on CDPH model estimates, LP.8.1 is predicted to be the variant with the highest and fastest growing proportion.

Additional COVID-19 Resources