(CNN) Daily US coronavirus cases have been ticking up recently, a trend medical experts have said they won't want to see as a potentially complicated flu season approaches.
New daily cases averaged about 39,700 over a week as of Thursday. That average has risen the past few days, to 13% higher than the week before, data from Johns Hopkins University show.
This comes after weeks of decline from a summer surge. It's well below the summer peak average of 67,300 on July 22.
But health experts have said they fear it might be too high to prevent big spikes this fall, as colder weather sends more people indoors, increasing the risk of spreading both Covid-19 and the flu.
"We really need to see flu vaccination uptake increased across the Northern Hemisphere ... especially this year," Maria Van Kerkhove, the World Health Organization's technical lead for coronavirus, said Friday. "Because we have a tool against flu ... that will help, and it will particularly help vulnerable populations."
Health experts have said Covid-19 colliding with flu season could strain health care capacity, partly because in normal years many Americans are hospitalized with flu.
A possible silver lining: The nation's top infectious disease expert says the US won't necessarily see the worst of flu seasons.
Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, pointed Thursday to the Southern Hemisphere, where it's late winter, and where Australia has experienced an almost non-existent flu season.
A new study published by the US Centers for Disease Control and Prevention also suggests that measures taken against Covid-19, like social distancing and teleworking, could lead to a mild flu season.
"The key point here is still this: No. 1, if we don't want to see a double whammy (of Covid-19 and flu), get your flu shot," Dr. Abdul El-Sayed, epidemiologist and former Detroit health commissioner, said Friday.
"No. 2, make sure you wear a mask. No. 3, keep practicing safe social distancing."
More than 6.7 million Covid-19 infections have been officially reported in the US since the start of the pandemic, and at least 198,477 people have died, according to Johns Hopkins.
The country has averaged 838 Covid-19 deaths a day over the past week -- a rate below where it was weeks ago. Daily deaths hovered above 1,000 for 25 straight days from late July into mid-August.
The CDC on Friday rolled back controversial changes made last month to guidance for testing people who do not have symptoms of coronavirus.
Like the guidance before August's change, Friday's new language stresses that anyone who has been in contact with an infected person should be tested, whether they are exhibiting symptoms or not.
In August, the CDC site had been changed to say that people without symptoms do not necessarily need to be tested, even if they've been in close contact with someone known to have the virus, unless the asymptomatic person is "a vulnerable individual," or if that person's health care provider or a public health official recommends the person take one.
The move was heavily criticized by doctors and health agencies.
Two sources recently confirmed to CNN that the August alteration was not written by CDC scientists and was posted online before it had undergone the normal scientific review process.
Details about the background on the August changes were first reported Thursday by The New York Times.
A senior federal health official close to the process had previously told CNN that the August change in Covid-19 testing guidance was the result of pressure from the Trump administration, saying, "It's coming from the top down."
In a statement Thursday night, CDC Director Dr. Robert Redfield told CNN, "The guidelines, coordinated in conjunction with the White House Coronavirus Task Force, received appropriate attention, consultation and input from task force experts."
The US Postal Service had planned to distribute 650 million face coverings for the Trump administration in April to curb coronavirus, according to newly obtained internal documents reviewed by CNN.
But the White House scrapped those plans to avoid sparking "concern or panic" among Americans, senior administration officials told The Washington Post.
The documents obtained by the transparency group American Oversight show the Postal Service was doing this in partnership with the White House Coronavirus Task Force, the Department of Health and Human Services, and "a consortium of textile manufacturers."
USPS was planning to ship the masks in April and to prioritize areas "which HHS has identified as experiencing high transmission rates of Covid-19," according to a draft USPS release.
A separate draft media response statement said the packages would include "five reusable face cloths, which can be used up to 15 times each."
The scrapped plan provides a fresh look at how the White House was responding to the pandemic in its early days. When reached by CNN, the White House declined to comment.