The coronavirus is still out there "and any time we are not careful, it can come back to bite us," former CDC Director Dr. Tom Frieden warned Monday on "Your World".

Frieden told host Neil Cavuto that although the United States is not among the countries considering a second lockdown to contain a recent increase in cases, Americans must act responsibly and understand that "there is no fairy tale ending for the pandemic -- not even a vaccine when we have one."

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"What we have to do is chip away at the risk and be ready to adapt," Frieden said. "That means making sure that we follow [those] three W's: wear a mask, watch your distance, wash your hands ... all of these things together chip away at that risk and enable us to get our activities back sooner and to keep them back.

"If we just rush back in," Frieden added, "we have to rush back out again and that is what you are seeing in some places around the world and around the U.S."

Frieden then floated the possibility of a winter surge in cases, telling host Neil Cavuto that the rate of positive tests could increase as temperatures drop.

"We may see more disease there, maybe," Frieden said. "We don’t know. What we do know is that we have a lot of control. How much COVID spreads depends on us. It depends on how long you spend indoors in poorly ventilated places with people who have been in places with a lot of COVID and aren't wearing masks."

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"If you take all of those risk factors and one by one you chip away at them, wear a mask, limit your time indoors near a lot of people…. You could make a big difference," he said.