Though younger, asymptomatic individuals are at lower risk of complications and death from COVID-19, they pose a risk of "unwittingly" transmitting the virus to elders and those with underlying medical conditions, Redfield said.
"And this could reflect a number of things, including the fact that people actually are hearing and understanding the messages, including the message that people who are at higher risk need to take more precautions", said Dr. Jay Butler, CDC COVID-19 response incident manager.
Over 20 million Americans have likely already had Covid-19, including millions of young people who were perhaps unaware they contracted the disease.
Before, the CDC said those 65 and older were at an increased risk of severe illness.
Florida reported 5,508 new COVID-19 cases on Wednesday, bringing the total to more than 114,000.
Previously, the CDC said that adults older than 65 were at increased risk for severe illness, but now says that the risk among adults increases steadily with age, and is not limited to those over 65. However, there was no higher risk of death for pregnant women.
Many in the U.S. have been seeking a return to something resembling normalcy as states have begun loosening virus-related restrictions, but Redfield continued to stress "many individuals in this nation are still susceptible".
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And certain people are more susceptible to very serious illness from COVID-19.The CDC points to consistent evidence from studies that a range of conditions are linked to more severe illness from COVID-19. Lifestyle-related diseases including Type-2 diabetes and obesity are among the most common conditions in the U.S. These conditions can increase inflammation and tamp down the immune system.
The same advice holds for people who live with or care for people at higher risk, Redfield added.
Florida is now experiencing a surge in COVID-19 cases, as the state reached a new record for single-day infections on Wednesday with 5,511 new cases. "It's significant", he emphasized.
The current CDC count for coronavirus cases in the United States is 2,336,615 - the most of any country in the world.
"The most powerful tool that we have is social distancing", Redfield said.
"As we go into the fall, in the winter, these are going to be really, really important defence mechanisms".