NEWMARKET, ONT. -- Seven cases of the highly contagious mutant strain of the coronavirus have been confirmed in York Region.

York Region medical officer of health, Dr. Karim Kurji, says detecting community transmission of the U.K. variant is "significant."

The first known case is a woman in King Township who travelled to the U.K. for business and failed to self-isolate immediately after returning to Ontario. She then infected three others in her home, with each family member testing positive for the coronavirus variant.

"Normally, we only expect about 15 per cent of the close contacts to get COVID-19, not 100 per cent of the close contacts," Kurji says.

The region's top doc says the U.K. variant appears to be remarkably more infectious.

A married couple from Georgina also tested positive for the coronavirus variant, along with a Richmond Hill resident. None of whom travelled abroad or came into contact with the King Township woman.

Kurji says the incident rates in York Region are now the second-highest in Ontario, second only to Peel Region.

Health officials believe the virus is spreading throughout the GTA.

"Hopefully, if we can continue the measures that we have been making, we'll be able to prevent its ongoing transmission," Kurji says.

Still, Kurji admits it's too early to know how prevalent the U.K. variant of the virus is in York Region. He adds the only protection residents have is to remain home as advised by the province and stick to those in the household as the only close contacts.