With local COVID-19 infections slowly rising, Toronto’s public health chief is worried people are starting to burst out of their social “bubbles.”

“We are at a critical time in the pandemic and I need your help,” Dr. Eileen de Villa told a briefing Wednesday after an online city “dashboard,” green since Aug. 10, reverted to yellow warning status because the infection rate is creeping up.

“We’re going to be living with this virus for the foreseeable future so it’s critical that everyone understands that this a marathon and not a sprint.”

De Villa said some people have told her they think life can return to “normal” now, with increased socializing, after daily new infections fell to low double-digits over July and the first part of August.

But public health advice for people to maintain “bubbles” — groups of up to 10 who can have close contact without masks — stands. Others should keep at least two metres between them and, if they can’t, wear masks.

“It is critical to remember you can only belong to one bubble,” de Villa said.

With new infections predictably trending up during Stage 3 reopening, and expected to worsen as kids return to school, Torontonians must also stick to hand washing and other precautions, or risk a deadly fall and winter, she added.

De Villa noted increased COVID-19 hospitalizations in British Columbia and Alberta, often linked to social gatherings, and a return to record infection numbers in some communities after virus levels had steeply dropped.

“This is very concerning,” she said. “I am calling on everyone to do absolutely everything you can to keep reducing the spread of this virus.”

Some people on social media are questioning the effectiveness of social bubbles given that children will soon be together at school and then returning home.

“The difficulty with the (province’s) weak approach to school opening is that there’s going to be tremendous cross-linkages across bubbles,” said Dr. David Fisman.

The University of Toronto epidemiologist has urged the Ontario government to adopt stricter back-to-school guidelines, including smaller classes and more outdoor activities. But that doesn’t mean Torontonians should abandon bubbles, he said.

“I think it makes sense for people to try to keep their contact numbers down, but the between-bubble linkages via schools mean that de facto contact numbers in the city will increase sharply with school opening.”

David Rider is the Star’s City Hall bureau chief and a reporter covering city hall and municipal politics. Follow him on Twitter: @dmrider