Longest-serving U.S. Sen. Chuck Grassley has tested positive for COVID-19. 

Grassley is 87 years old and serves as president pro tempore of the United States, putting him in third in the line of succession. According to an issue from Grassley, he discovered he had been exposed early Tuesday. 

Grassley said he will continue to follow his doctor’s orders and the Center of Disease Control and Prevention (CDC) and quarantine.

According to the statement, Grassley’s offices will remain open across Iowa and in Washington. Grassley’s positive case came after Iowa Gov. Kim Reynolds recently announced new mitigations to help prevent the spread of COVID-19, including a statewide mask mandate. 

Iowa Sen. Joni Ernst and other Iowa officials tweeted their prayers for a full recovery to Grassley. In Iowa, more than 191,000 people have tested positive, with an individual positivity rate of 17.1 percent and a total of 2,028 deaths. 

Grassley is one of six Republican members of the Senate to test positive for COVID-19. According to NPR, by November, more than 25 members of Congress and at least 150 workers have tested positive or presumed to have tested positive. 

Grassley has yet to disclose how he was exposed. The CDC states individuals of 85 years or older are at the “greatest risk for severe illness from COVID-19,” and factors such as underlying medical conditions can increase the risk for severe illness. 

“I am keeping up on my work for the people of Iowa from home,” Grassley’s statement read. “I appreciate everyone’s well wishes and prayers, and look forward to resuming my normal schedule when I can.”