CDC: For every coronavirus case reported, 10 likely went unannounced

For every COVID-19 case reported, 10 additional infections likely went unannounced, according to best estimates from the Centers for Disease Control and Prevention.

In a call with reporters on Thursday, CDC Director Dr. Robert Redfield said, “In the past, we didn’t really aggressively pursue diagnostics in young asymptomatic individuals.”

Asymptomatic COVID-19 individuals are of great concern to public health officials and lawmakers due to their ability to spread the virus without knowing they're sick themselves.

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.

He said the agency will continue to do “fairly extensive” surveillance nationwide through antibody testing.

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Officials attributed a large proportion of increasing case numbers to younger people.

“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. “So, it's possible that we're seeing a smaller proportion of infections in older people because there actually is less exposure.”

Officials said there isn’t an “exact cut off of age” where people should or should not be concerned about infection.

Given the upcoming July 4 holiday, CDC officials said everyone can take steps to prevent COVID-19 infection, including social distancing, frequent hand washing, staying away from others if ill and wearing face coverings if social distancing is not possible.

Fox News' Chris Ciaccia contributed to this story.