WASHINGTON — Sens. Roger Wicker, R-Miss., Angus King, I-Maine, and John Hickenlooper, D-Colo., announced Thursday that they have tested positive for the coronavirus, becoming the latest members of the Senate to announce breakthrough infections in recent weeks.

Earlier this month, Sen. Lindsey O. Graham, R-S.C., said he had tested positive for the virus. All four senators have been vaccinated.

In a statement, Wicker's communications director, Phillip Waller, said the senator tested positive Thursday morning "after immediately seeking a test due to mild symptoms."

"Senator Wicker is fully vaccinated against COVID-19, is in good health, and is being treated by his Tupelo-based physician," Waller said. "He is isolating, and everyone with whom Senator Wicker has come in close contact recently has been notified."

King announced that he took a test Thursday morning at his doctor's suggestion after he had begun feeling "mildly feverish" on Wednesday. The test came back positive.

"While I am not feeling great, I'm definitely feeling much better than I would have without the vaccine," King said in a statement Thursday afternoon. "I am taking this diagnosis very seriously, quarantining myself at home and telling the few people I've been in contact with to get tested in order to limit any further spread."

King also noted the steps he has taken since last year to protect himself and others, including "driving up and back to Maine dozens of times rather than flying until only recently, Zoom calls instead of attending Senate hearings in person, voting quickly on the floor while remaining masked, regular testing for me and my staff, and receiving the vaccinations when it was my turn to get them earlier this year."

Later Thursday afternoon, Hickenlooper announced that he had tested positive with a breakthrough case of the virus.

"I feel good but will isolate per docs instructions," Hickenlooper said in a tweet. "I'm grateful for the vaccine (& the scientists behind it!) for limiting my symptoms. If you haven't gotten your shot-get it today! And a booster when it's available too!"

King is 77 and a prostate cancer survivor. Wicker is 70, Graham is 66 and Hickenlooper is 69.

While the summer spread of the virus's more-contagious delta variant has meant rising case numbers again in many parts of the country, data from the Centers for Disease Control and Prevention shows that breakthrough infections remain rare. The potential for those breakthrough cases to carry viral loads similar to that of unvaccinated people means that the possibility of transmission remains.

On Tuesday, Texas Gov. Greg Abbott, R, announced that he had tested positive for the coronavirus. In a video posted on Twitter, Abbott said that he has been vaccinated against the coronavirus "and that may be one reason why I'm really not feeling any symptoms right now."

Abbott is among the Republican governors who have resisted public health mandates aimed at stemming the tide of the delta variant.

The Washington Post's Paul Kane contributed to this report.