On Thursday, Mr Cassidy’s office announced that he had become just the second senator to have contracted coronavirus, after Republican Rand Paul tested positive for Covid-19 in April, according to CNBC.
The senator confirmed that he will now quarantine for 14 days and notify anyone he has been in contact with recently, but the 62-year-old did not reveal the severity of his symptoms.
In a statement, Mr Cassidy, who represents Louisiana, said: “I am strictly following the direction of our medical experts and strongly encourage others to do the same.”
Although only two senators have tested positive for Covid-19, at least nine representatives in Congress have contracted the virus, including Democrat Joe Cunningham and Republican Mike Kelly, according to CNN.
In July, face masks were mandated on the House floor by speaker Nancy Pelosi, after Texas representative Louie Gohmert tested positive for Covid-19.
Mr Gohmert, who publicly opposed masks and refused to wear face coverings while walking through Congress, said that he would only wear one if he tested positive for coronavirus, according to Newsweek.
After his diagnosis, he claimed that he had worn his mask more in the two weeks leading up to contracting Covid-19, than in the months previous, and said: “I can’t help but wonder if by keeping a mask on and keeping it in place if I might have put some of the virus onto the mask and breathed it in. I don’t know.”
The Senate has not implemented a mask mandate, but senators including Mr Cassidy are regularly seen wearing face coverings in the chamber and around the Capitol Building, according to CNN.
Senators and House representatives are currently on their summer recess, after they left Washington, DC, last month without an agreement on future coronavirus relief, as Democratic leaders and the White House could not agree on a package.
Mr Cassidy has been a strong advocate for coronavirus aid and has called for at least $500bn (£448.8bn) more to be given to state and local governments in the fifth round of stimulus relief, while the Trump administration has only offered $150bn (£134.6bn).
The Democrats have asked for at least $900bn (£681bn), and speaking during an interview with CNBC last week, Mr Cassidy said that his Republican colleagues need to increase their offer, and added: “We need to get something passed.”
According to Johns Hopkins University some 5.5m people have now tested positive for coronavirus in the US and the death toll has reached 173,882.