By Stephanie Stahl

PHILADELPHIA (CBS) — The head of the Centers for Disease Control and Prevention warns the fall season could be the worst we’ve ever had with a double dose of sickness from COVID-19 and the flu.

This comes as coronavirus numbers are increasing in Philadelphia.

Nationally, five million people have been infected with COVID-19 and the death rate on Wednesday was the highest it’s been in months.

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Federal health officials say it could get worse if people don’t take precautions more seriously.

In Philadelphia, the cases are trending up again after weeks on the decline.

“The positivity rate was right at 5%, which is slightly higher than we’ve been running over the last week or so,” Philadelphia Health Commissioner Dr. Thomas Farley said.

The health commissioner says it’s not clear yet if the uptick is the result of sporadic test results being delayed and then coming in clumps.

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Nationally, deaths from COVID-19 on Wednesday were the highest since May, and it comes with dire warnings from the head of the CDC.

“This could be the worst fall from a public health perspective we’ve ever had,” CDC Director Dr. Robert Redfield said.

Redfield says the upcoming flu season could compound the coronavirus crisis unless people wear masks.

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“We all got to do it,” Redfield said.

The other precautions of social distancing and avoiding crowds will be especially important in the fall.

“It could be very bad at that time,” Farley said. “If people wear masks though and do this really diligently, we might be able to limit the amount of coronavirus as well as the amount of influenza that we see.”

Health officials say flu shots will be critical.

“Most respiratory viruses get worse in the fall,” Farley said.

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Farley said contract tracing shows most people (41%) are being infected by someone in their home, 18% from travel, and about a third of those with the virus who’ve been reached say they’ve had no contacts.

“I don’t think they’re being totally truthful,” Farley said. “I think they’re basically not cooperating. People are reluctant to give us the names of folks that they’ve been around. There’s a lot of fear and mistrust out there.”

Farley also discussed fall sports on Thursday and said it was unlikely that Eagles fans would be allowed in Lincoln Financial Field for the home opener on Sept. 20.

Mayor Jim Kenney says guidance on all sporting events will depend on what’s happening with the virus.

Stephanie Stahl