A very troubling trend is emerging right before the holidays as pockets of unvaccinated New Yorkers are driving up COVID-19 cases statewide.

The least vaccinated regions in New York are seeing the highest spike in COVID-19 cases, which is prompting another stern warning from officials.

Cases jumped nearly 30% over the past week while hitting the highest positivity rates since the spring. Overall, the statewide positivity rate is 3.8% -- the highest since April.

The Mid-Hudson region has one of the lowest positivity rates in the states at just under 3% with 72% of people with one COVID-19 shot.

Western New York has the state’s highest positivity rate at 10%, and 66% of people there have one COVID-19 shot, which is what health experts believe is the reason for the surge.

"The expectation of a surge is very much tied to the percent of unvaccinated in a county or community," says Dr. Robert Amler, the dean of New York Medical College School of Health Sciences.

Gov. Kathy Hochul is encouraging people to get their first doses or booster shots ahead of Thanksgiving, fearing the negative impact indoor gatherings, especially among the unvaccinated, will have on the state's fight against the virus.

"It is far worse to contract COVID over the holidays than it is to have to deal with the effects of your booster shot," said Hochul.

Westchester's total number of positive tests was up 30% last week over the week before - topping 1,000 over the seven days, according to state data.

This bodes well for the future of cases in Westchester, where 80% of the population had at least one shot, which is among the highest rates in New York.