It comes just two weeks after Prime Minister Boris Johnson announced the removal of the remaining restrictions to prevent the spread of the virus, including mandatory isolation for those who test positive and wearing masks in shops and other enclosed public spaces.
Prof Arden said the spread of the virus was the “completely expected result” of the lifting of the restrictions.
And she feared that cases could be even higher than reported, as fewer people were taking confirmatory PCR tests.
She said: “The removal of all legal restrictions and protections sends a message out to the public. If it’s down to individual responsibility, yes, of course there are those of us who will continue to use face masks and keep our distance and do blended working, but if the general tone of the message is we are removing restrictions, then perhaps the message people get is it’s all over.
"What we are seeing is very clearly that it wasn’t all over when the legal restrictions were lifted, but also it’s very clear that it’s not all over now.”
Prof Ardern said rates of coronavirus were going up in eight of the 10 boroughs in Greater Manchester.
"I think one of the concerns is we have is because we have dropped off the testing regime, it makes it much more difficult to track community transmission. If we are only testing people, for example, when they are admitted to hospital, it’s a bit late then to stop community transmission. It’s very challenging in terms of getting our surveillance right,” she said.
It is thought many people have stopped following measures introduced during the pandemic to prevent the spread of Covid-19, such as washing their hands, keeping a distance from others, opening windows and wearing masks.
That is leading to more people catching the virus – but also other illnesses such as flu.
Prof Ardern said: “It’s another respiratory virus and those respiratory public health protections were not just protecting us against Covid, but protecting us against flu as well.
"We are starting to see a late flu season to compound the situation.”
She said it had not yet led to more people being admitted to hospital locally with flu, but numbers had flattened rather than dropping off as they normally would in the spring.
And other areas of the country were seeing more admissions, so it was “likely” this would also happen in Wigan.
Prof Ardern urged people to resume following infection control measures used in the pandemic to help stop the spread of both flu and coronavirus.
She also encouraged everyone to get the flu jab and Covid-19 vaccinations, whether the primary course or boosters.
She said: “The key message is that Covid is very definitely still here. I think what we are seeing is people dropping their guard in terms of wearing face marks in enclosed public spaces, keeping windows open, hand washing and sanitising. They really need to think about doing that.”