KITCHENER -- Local health officials and provincial leaders are urging adults to skip Halloween parties this year due to the COVID-19 pandemic.

Medical Officer of Health Dr. Hsiu-Li Wang said she's worried about what adults are planning this weekend and how it could impact local numbers.

Public health officials have issued warnings for anyone heading out to trick-or-treat this year, encouraging people to stick with their immediate households and wear face masks.

Dr. Wang said Friday that she's concerned that parties planned this weekend could lead to an increase in COVID-19 cases in the future.

"There are lots of clusters of cases and outbreaks of cases caused by people having parties, adult parties," she said.

Guelph's top doctor echoed Dr. Wang's concerns, adding that 60 per cent of new cases in that area were spread at recent gatherings.

"They were predominantly due to private social gatherings and many of them were related to the Thanksgiving weekend," Dr. Nicola Mercer said. "As we look forward to Halloween, my number one message to everyone out there is please do not have a Halloween party."

Dr. Wang said possible spread from this weekend likely won't show up for a week and a half. The number of cases in the future will depend on how people behave this weekend.

Provincial Minister of Colleges and Universities Ross Romano issued a statement on Friday to remind students and staff at post-secondary institutions to celebrate Halloween safely this year.

"With Halloween weekend upon us, I remind Ontario's postsecondary students and faculty to follow public health advice and measures in order to ensure you are keeping yourself, your friends, and your families safe," Romano's statement said in part. "We understand that students want to socialize and celebrate during Halloween, but we need to do our part this weekend and help reduce the spread of COVID-19."

The province says people should only gather with people in their household and stay home if they're feeling sick.

"I also want to remind students that violating public health guidelines may result in potentially serious sanctions being imposed by your particular postsecondary institution, or local public health/ municipal officials," Romano said. "However, there is no sanction more serious than to cause, or contribute to the spread of COVID-19 to your friends, family, and loved ones. Our students are all adults and I know they will act responsibly."