Rep. Mario Diaz-Balart, R-Fla., speaks about Cuba during the House Republicans weekly news conference on Wednesday, Feb. 26, 2020, in reaction to Bernie Sanders recent comments about Cuba.

Two members of the U.S. House of Representatives have become the first members of Congress to test positive for COVID-19, the illness caused by the novel coronavirus.

On Wednesday, both Mario Diaz-Balart, a Florida Republican, and Utah Democrat Ben McAdams announced they were in self-quarantine after testing positive.

At least 10 other members of Congress also announced on Wednesday and Thursday that they were in self-quarantine as a precaution because of exposure to people who have tested positive, many of whom had contact with Diaz-Balart and McAdams.

Sen. Cory Gardner, R-Colorado, announced earlier in the week that he was in self-quarantine "because I came into contact last week with a Coloradan who later tested positive for #COVID19."

On Wednesday night, a spokesman for Republican Party Chairwoman Ronna McDaniel, who had been in self-quarantine after having flu-like symptoms, said McDaniel tested negative for COVID-19.

President Donald Trump's outgoing chief of staff, Mick Mulvaney, was in self-isolation in South Carolina as of Tuesday after having contact with his niece, whose results of a coronavirus test were pending.

Diaz-Balart said in a statement, "I want everyone to know that I am feeling much better."

"However, it is important that everyone take this extremely seriously and follow [Centers for Disease Control and Prevention] guidelines in order to avoid getting sick and mitigate the spread of this virus," Diaz-Balart said.