The 87-year-old U.S. Senator who is third in the line of presidential succession has been diagnosed with COVID-19, the BBC reports.

Chuck Grassley, the longest-serving Republican in the upper chamber, is currently in quarantine after testing positive for novel coronavirus.

The diagnosis forced him to miss a vote in the Senate on Tuesday for the first time in 27 years.

Grassley, a native of Iowa, is the sixth US senator known to have been infected with novel coronavirus. The other five who fell ill have since recovered.

On Tuesday, Grassley issued a statement regarding his diagnosis, saying: "While I still feel fine, the test came back positive for the coronavirus. I am continuing to follow my doctors' orders and CDC [Centers for Disease Control and Prevention] guidelines."

Grassley was initially elected to the Senate in 1980, and in his role as president pro tempore of the Senate, he would take the reins in leading the nation should President Trump, Vice President Mike Pence, and House of Representatives speaker Nancy Pelosi become unable to do so.