At least 18 members of the U.S. House of Representatives and Senate - nine Republicans and seven Democrats - have tested positive or are presumed to have had COVID-19, with Representative Jahana Hayes becoming the latest on Sunday.

Representative Jahana Hayes

Hayes, a Connecticut Democrat, tested positive for COVID-19 and will quarantine for 14 days, she said on Twitter on September 20, adding that she was asymptomatic except for breathing issues, which were being monitored.

"I have taken every possible precaution and still contracted coronavirus," she said on Twitter.

Resident Commissioner Jenniffer Gonzalez Colon

Gonzalez, resident commissioner of Puerto Rico and the U.S. territory's sole representative in Congress, said that she tested positive for COVID-19 on Facebook, days after accompanying federal officials on a visit to Puerto Rico's pharmaceutical industry.

Senator Bill Cassidy

Cassidy, a Louisiana Republican, decided to self-quarantine for 14 days and contact those with whom he may have had contact after testing positive for the virus, according to a statement released by his office on August 20.

"I am strictly following the direction of our medical experts and strongly encourage others to do the same," the 62-year-old senator, himself a physician, said in the statement.

Representative Rodney Davis

Davis, an Illinois Republican, said in a statement on August 5 that he tested positive for the novel coronavirus after running a fever.

"If you're out in public, use social distancing, and when you can't social distance, please wear a mask," Davis, 50, said in the statement.

Representative Raul Grijalva

Grijalva, an Arizona Democrat, tested positive for the coronavirus and went into isolation, he said in a statement on August 1.

Grijalva expressed frustration with the reluctance of some Republican lawmakers to wear masks, which can slow the spread of the coronavirus.

Representative Louie Gohmert

The Texas Republican, 66, a staunch conservative, said on July 29 he tested positive in a prescreening at the White House but did not have any symptoms.

"It's really ironic, because a lot of people have made a big deal out of my not wearing a mask a lot. But in the last week or two, I have worn a mask more than I have in the whole last four months.”

Representative Morgan Griffith

The Virginia Republican, 62, a member of the conservative Freedom Caucus, said in mid-July that he had tested positive. His office said he did not have significant symptoms.

Representative Tom Rice

The South Carolina Republican, 62, said on Facebook in mid-June that he, his wife and son had all tested positive for the coronavirus but all were "on the mend."

Senator Tim Kaine

The Virginia Democrat and former vice presidential candidate, 62, said in mid-May that he and his wife had tested positive for coronavirus antibodies.

Senator Bob Casey

Casey, 60, a Pennsylvania Democrat, tested positive for coronavirus antibodies in May, but pledged to keep wearing a mask.

Representative Neal Dunn

The Florida Republican, 67, a former surgeon, said in April that he had gone to the emergency room after not feeling well and later tested positive for the coronavirus.

Representative Joe Cunningham

A Democrat from South Carolina, Cunningham, 38, said on March 27 he had tested positive for the coronavirus.

Representative Mike Kelly

Kelly, 72, a Republican from Pennsylvania, tested positive for the coronavirus in late March at a drive-through testing site. He told an interviewer that it took him about a month to recover and that he lost 14 kilograms.

Senator Rand Paul

The Kentucky Republican, 57, said on March 22 that he had tested positive and was in quarantine, but was feeling fine. After he returned to work, Paul still did not wear a mask and said it was because he believed he was immune.

Representative Mario Diaz-Balart

The Florida Republican, 58, tested positive in mid-March, saying the symptoms "pretty much hit me like a ton of bricks." After his health improved, Diaz-Balart said he would participate in a plasma donation program to help people with serious or life-threatening infections of COVID-19.

Representative Ben Mcadams

The Utah Democrat also caught the virus in March. He was hospitalized and needed oxygen. After his release, he warned others to take the virus seriously. "I'm young, I'm 45 years old, I'm healthy, I exercise every day, and it hit me really hard," he told ABC.

Representative Nydia Velazquez

Velazquez, 67, a Democrat from New York, said in March that she had been diagnosed with a presumed case of the coronavirus, although she had not been tested.

Representative Seth Moulton

The Massachusetts Democrat, 41, said in March that he and his wife were in self-quarantine after experiencing coronavirus-like symptoms. The congressman said they did not, however, qualify for testing.