SAN JOSE (CBS SF) – Health officials in Santa Clara County reported Wednesday new cases of COVID-19 variants believed to be easier to spread, reminding residents to continue following  prevention measures.

Officials said in a statement that they have found the county’s second case of B1351, also known as the South African variant. The case, which was reported in early March, is believed to have resulted from community transmission.

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It is the fourth confirmed case of B1351 reported in California so far. A previous case reported in the county last month resulted from travel, health officials said.

“This latest case confirms that we do have community transmission, and reminds us to not let down our guard in the middle of this pandemic,” said Santa Clara County Public Health Director Dr. Sara Cody.

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The health department also said the number of cases from variant B117, also known as the U.K. or British variant, has increased to 15 in Santa Clara County. Officials cautioned the true level of spread is not known since they can only perform genomic sequencing on only a fraction of the cases. Earlier this week, officials in Contra Costa County announced their first two cases of B117.

Officials reiterated that travel remains strongly discouraged and urged people to continue wearing masks in public and to receive vaccines once eligible. The county also noted while many areas have loosened restrictions to allow more activities, they can be high-risk and minimizing potential exposure is still urged.

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“Even with these variants circulating in our community, the best tools to protect ourselves and our loved ones remain familiar to us and are available now,” said deputy health officer Dr. George Han. “Wear your masks, keep your distance from others, avoid gatherings, especially indoors, and get vaccinated when it’s your turn.”