There were initially four states slated to vote, but Ohio was called off on Monday night after Gov. Mike DeWine filed suit to block his state's primary, citing concerns that poll workers could be exposed to to the virus.
The St. Patrick's Day primaries are also the first since Joe Biden and Sen. Bernie Sanders faced off in a stripped down, one-on-one debate in Washington, D.C., on Sunday night.
Primaries being held in Arizona, Florida and Illinois.
Extra coronavirus precautions?
In a joint statement on Friday, the secretaries of state of all three states (and Ohio at that time) said they "are working closely with our state health officials to ensure that our poll workers and voters can be confident that voting is safe."
"Further, guidance from voting machine manufacturers on how best to sanitize machines, guidance from CDC on best practices for hand washing, and guidance from our respective state health officials is being provided to every polling location," the statement said.
When do polls close?
Last polls close at 8 p.m. ET in Florida, and at 8 p.m. ET in Illinois and 10:00 p.m. ET in Arizona.
How many delegates at stake?
There are 441 delegates are up for grabs — 219 in Florida, 155 in Illinois and 67 in Arizona.
How are they allocated?
Two types of delegates can be awarded, statewide (or at-large) delegates and district-level delegates.
Candidates must receive at least 15 percent of the vote statewide to receive any statewide delegates and must also meet the 15 percent threshold in a congressional district to receive any district-level delegates. Those who fail to meet 15 percent will be locked out.
How many delegates to win?
To capture the Democratic nomination on first ballot, a candidate must receive support from at least 1,991 of the total 3,979 pledged delegates. According to the NBC News delegate tracker, Biden is currently leading the race with 860, Sanders has 706 and Hawaii Rep. Tulsi Gabbard has two.
When's the next primary?
Georgia was up next, but the secretary of state announced he is pushing back the March 24 primary until May 19 because of coronavirus concerns. That was set to followed by Puerto Rico on March 29, but the Democratic Party there has asked the legislature to postpone the primary to April 26. Four states are scheduled to vote April 4, but one of those, Louisiana, has already postponed its primary until June.
Figures who have tested positive for coronavirus
Figures who have tested positive for coronavirus
Last week, Tom Hanks and Rita Wilson announced that they had tested positive for COVID-19 after contracting it in Australia, where Hanks was filming a movie.
"We felt a bit tired, like we had colds, and some body aches," the Oscar-winning actor shared on Instagram. "Rita had some chills that came and went. Slight fevers too. To play things right, as is needed in the world right now, we were tested for the Coronavirus, and were found to be positive."
"Well, now. What to do next? The Medical Officials have protocols that must be followed. We Hanks’ will be tested observed, and isolated for as long as public health and safety requires. Not much more to it than a one-day-at-a-time approach, no?"
Idris Elba took to Twitter on Monday morning to announce that he, too, contracted the virus. The actor was at the same conference in Webley as Sophie Trudeau, who also tested positive.
He shared with his fans:
"This morning I tested positive for Covid 19. I feel ok, I have no symptoms so far but have been isolated since I found out about my possible exposure to the virus. Stay home people and be pragmatic. I will keep you updated on how I’m doing. No panic.
Sophie Gregorie Trudeau, the wife of Canadian prime minister Justin Trudeau, was announced to have tested positive for the virus last week.
Her symptoms developed after attending a conference in Britain in early March. The prime minister is not showing symptoms and will not be tested, but will remain under quarantine.
Kristofer Hivju, best known for his role as Tormund on "Game of Thrones," took to Instagram on Monday to reveal he was self quarantining with his family in Norway.
"We are in good health,” he wrote. “I only have mild symptoms of a cold. There are people at higher risk for who this virus might be a devastating diagnosis, so I urge all of you to be extremely careful; wash your hands, keep 1,5 meters distance from others, go in quarantine; just do everything you can to stop the virus from spreading.
Olga Kurylenko, who starred in the James Bond movie “Quantum of Solace,” announced this weekend that she has contracted COVID-19, the disease caused by the new coronavirus.
“I’ve actually been ill for almost a week now,” she wrote on Instagram. “Fever and fatigue are my main symptoms. Take care of yourself and do take this seriously!”
Donavan Mitchell and Rudy Gobert, both players on the Utah Jazz basketball team, have tested positive for the virus. Gobert was the first NBA player to test positive, which prompted the suspension of the rest of the basketball season.
Callum Hudson-Odoi, a forward for the Chelsea football team, tested positive for the virus, in addition to Arsenal coach Mikel Arteta. Following the announcement, all professional soccer games in England have been postponed.