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Highly infectious Omicron variants fuel increases in COVID-19 cases


Increases in new Omicron variants continue to fuel high transmission in LA County, with cases and hospitalizations currently much higher than they were at this time last year, showing just how infectious the current Omicron variants and sub-lineages are.

For specimens collected for the week ending May 21, 98 percent of specimens continue to be BA.2 and its sublineages. However, the proportion of the BA.2 Omicron variant itself, excluding its sublineages, appears to be plateauing, and continues to account for about half of the specimens sequenced in the County. The BA.2.3 Omicron sublineage has decreased, accounting for only about 3 percent of specimens in the most recent week. In contrast, BA.2.12.1 sublineage accounted for 42 percent of positive sequenced specimens, a small increase from the previous week. Nationally, the Centers for Disease Control and Prevention (CDC) predicts that BA.2.12.1 will account for 62 percent of specimens collected the week ending June 4.

The BA.4 and BA.5 sub variants continue to remain rare in LA County, but a few cases are being detected every week. The CDC estimated that, across the country, these two variants combined may have increased from about 1 to 13 percent of specimens collected in the past month. This suggests they may have the ability to outcompete other circulating variants. There is also concern that they may be able to cause re-infections in people who have already been infected by other Omicron sub variants.

The current high case numbers are also in stark contrast to the average number of cases last year, nearly 25 times higher in fact, as there were only 190 average daily new cases in the middle of June 2021.

The highly infectious variants and sub-lineages fueling the recent higher case numbers have translated to more than double the number of people severely ill and needing to be hospitalized than a month ago.

“As always, we extend our deepest sympathies and prayers for healing to everyone mourning the loss of a loved one from COVID,” said Dr. Barbara Ferrer, PhD, MPH, MEd, Director of Public Health. “The highly infectious Omicron variants are providing uncertainty about the trajectory of this recent surge in cases. At this time last year, we benefited from a much lower rate of transmission associated with a more stable virus. The concern with the rapidity of emerging highly infectious variants is that for each new variant, we need to reassess how much the new strain evades vaccine protection, causes severe illness, and avoids detection with current tests.

“And to be dominant, the new strains are likely to be even more infectious than the previous strains,” she added. “Until we have a more precise understanding of how the new viral strains interact with us and our community, we need to remain vigilant and cautious. This includes layering protections to keep those most vulnerable as safe as possible, including wearing masks indoors, getting tested before gathering or attending events, and staying home if you are sick.”

A wide range of data and dashboards on COVID-19 from the Los Angeles County Department of Public Health are available on the Public Health website at