By Maria Medina

SAN JOSE (KPIX) — The COVID Delta variant surged through the country this summer but the infection rate is now dropping rapidly although experts warn another surge could be coming this winter.

“I do think the winter is going to be problematic for us,” said University of California Berkeley Professor and infectious disease expert John Swartzberg. “The weather’s going to get colder, people are going to be inside more…and then we got some holidays.”

For nearly two years, COVID-19 has proven to behave unpredictably, even throwing off some health experts. The highly-transmissible Delta variant drove up cases once again, but now many areas are seeing a sharp decline.

In California, the positivity rate was 7.2% on Aug. 1. This past Monday, it stood at 2.9%.

In Santa Clara County, the seven-day rolling average peaked at 364 new cases during this last surge on Sept. 2. On Friday, the county’s public health department reported 215 new cases.

The U.S. followed the same pattern that the UK and India did when the Delta variant caused a significant surge in COVID-19 cases and mysteriously began to decline.

“This random behavior with the virus is difficult to wrap our heads around,” Dr. Swartzberg said. “It is mysterious.”

But the doctor believes the state’s high vaccination rate, those with natural immunity after infection and the Bay Area’s willingness to follow health mandates could all be playing a role in the recent decrease in cases.

However, now health experts are warning another wave of cases could peak in the winter. University of California San Francisco epidemiology prof. George Rutherford, however, believes the spike this winter won’t be as dramatic as the summer surge.

“I think in much of the Bay Area we may have enough immunity and enough adherence to the other measures we’ve undertaken to slow things down so you don’t see a big spike,” Rutherford said.

Both Swartberg and Rutherford predict the pandemic will improve by next spring when more people are vaccinated, have natural immunity and the weather warms up so people aren’t inclined to stay indoors.

Swartzberg said we’ll learn to live with the virus when cases reach low levels and the pandemic will eventually cease to exist.

“It’s going to end,” said Swartzberg. “It’s going to take awhile to get there but we will get there.”