U.S. Sen. Amy Klobuchar said Monday her husband, John Bessler, a law professor at the University of Baltimore, is hospitalized after testing positive for COVID-19, the respiratory disease tied to the novel coronavirus.

Klobuchar, D-Minnesota and a one-time U.S. presidential contender, said in a post Monday at Medium:

John started to feel sick when I was in Minnesota and he was in Washington D.C. and like so many others who have had the disease, he thought it was just a cold. Yet he immediately quarantined himself just in case and stopped going to his job teaching in Baltimore. He kept having a temperature and a bad, bad cough and when he started coughing up blood he got a test and a chest X-ray and they checked him into a hospital in Virginia because of a variety of things including very low oxygen levels which haven't really improved. He now has pneumonia and is on oxygen but not a ventilator.

Klobuchar described Bessler as "exhausted and sick but a very strong and resilient person."

The U.S. has reported more than 40,000 cases of COVID-19 in all 50 states. More than 400 deaths have been attributed to the disease. At least one U.S. senator, Republican Rand Paul of Kentucky, has tested positive for COVID-19. U.S. Sen. Mitt Romney, R-Utah, placed himself in self-quarantine after Paul's announcement. The two senators had sat next to each other in recent days.

Klobuchar said she and her husband have been in different places for the last two weeks, "and I am outside the 14-day period for getting sick." Klobuchar said her doctor has not suggested she be tested for COVID-19.

Bessler was an adviser to Klobuchar's 2020 presidential campaign, which she suspended in early March. He has taught at the University of Baltimore since 2009 and became a tenured faculty member in 2014. His teaching career has included posts at Georgetown University Law Center, University of Minnesota Law School and the George Washington University Law School.

The pandemic has caused widespread disruption across industries and professions, as companies, law firms and law schools grapple with uncertainty, workforce demands and government closure orders. The Baltimore law school, like many others around the country, has turned to online learning amid the crisis.

"The campus will be open to employees classified as Essential for Pandemic Circumstances — On Campus. All campus events are canceled until further notice," the law school said in an advisory on the school's website.