Lambton Public Health reported a spike of 15 new COVID-19 cases Friday afternoon.

It’s the largest daily increase in Sarnia-Lambton since the pandemic began, surpassing the previous high of 13 on April 19.

The county’s first cases were reported March 25.

In a news release, the health unit said additional test results were received related to close contacts of cases reported earlier in the week.

Officials said contact tracing determined the cases are linked to a few of the same families, predominantly in a rural community, but with connections to family members in urban communities.

Direction was provided to the families to self-isolate and proceed to an assessment for testing.

Medical Officer of Health Dr. Sudit Ranade said they continue to investigate and support all cases.

“We expected early on this week that new cases may result, based on findings and determining the level of interaction for an infected individual,” Ranade said in a news release. “The importance of moving quickly to limit the transmission of the virus is a critical public health measure to reduce additional community spread.”

The health unit said as the follow-up with close contacts continues, additional individuals may be required to self-isolate and get a test, or be directed to self-monitor for symptoms due to limited contact. That could include risk settings such as workplaces.

Dr. Ranade urges the public to continue to take precautions and follow the public health safety measures.

“The virus can quickly spread among close contacts so keep your social circle small – limit is 10, and be very diligent if you choose to attend a larger gathering,” he said.

Public health safety measures include staying home when sick, practicing physical distancing with others outside your social circle, use good hand hygiene, and wearing a mask if required or if physical distancing is not possible.

Sarnia-Lambton’s total confirmed case count as of Thursday night was 302.