Handlung

The doctors of Grey Sloan Memorial Hospital succumb to an infection that spreads like wildfire. Cristina deals with a complex case involving siblings and Alex begins to consider his future in the hospital.

Previously on 'Grey's Anatomy': Cristina used Meredith's 3-D printer and made a heart conduit that got a lot of attention and has her under consideration for the Harper Avery Foundation Award. Jackson and April got married. Hunt broke up with his girlfriend. Alex threatened to go to Johns Hopkins, but decided to stay until Arizona got better. Arizona seems better. Hunt offered Webber the spot as director of the residency program. Derek went back on his promise to let Meredith focus on her work while he took a step back. He was offered a position running a program for the president. Alex was worried about Jo's aggressive tendencies.

'You Be Illin'': A kid sneezes on Arizona and she tells Alex she can feel the fact that she's going to be sick coming on. There's an ominous focus on everything she's touching -- door handles, her tablet, Alex's arm. Jackson and April get into the elevator and kiss a bit. Meanwhile, Hunt is announcing that there is a viral infection running through the hospital. He warns the staff to go home if they feel sick.

April checks on a young boy named Braden who has a compromised immune system. His parents keep urging him to stop touching his face.

One third of the residents are out sick and Webber urges the rest of them to "push through." Leah is already feeling sick but Webber won't let her leave.

Jo checks on a guy whose face is stuck in a tight smile because he has muscle tightening in his face, likely the result of tetanus.

Ivy McNeil, a girl who's been on the heart transplant list, is set for her procedure that day. Cristina wanted to spend all day with the conduit kids because it's Day 30 of the trial. She doesn't want anything to happen to the trial patients. She tasks Shane with watching them because she's going to handle the transplant.

April checks on Braden, who seems to be showing signs of having the virus. April wants to move him into isolation immediately as she looks around and sees a bunch of people coughing and sneezing.

April tells Braden's parents that the bump on his forehead is a rapidly growing infection.

Derek is practicing a speech he's going to give to 50 scientists about the White House project.

Cristina brings Ivy to the O.R. for surgery, but asks for a kiss first.

Jackson checks on Braden, but it's clear he's sick when comes out of Braden's room. Bailey has taken an interest, as she used to be Braden's doctor.

Webber asks Leah to walk a patient through the procedure he's about to undergo, but Leah has fallen asleep standing up. Meredith wakes her up and Leah works through it, trying to stop from throwing up.

Meredith is worried that Derek is getting sick, but he insists he doesn't get sick. A European doctor, Dr. Strauss, has made the trip to hear Derek's speech. Derek is excited, but now even more nervous. Dr. Strauss is excited for Derek's talk, but says he hopes it's not "a complete waste of my time."

Shane is checking parents of the "conduit kids" because letting them in to see their children, trying to ensure the kids don't get sick.

Jo is still trying to the tetanus patient to take medicine that could save him, but he's insisting it's poison and refusing to take it. He starts to convulse and Jo tries to hold him down. Suddenly, his arm snaps in her hands.

Alex and Arizona are in surgery with Dr. Lebackes, who has "Atomic Dog" blasting in the background while operating. Alex seems annoyed. He has all the nurses singing and dancing along.

Callie looks at X-rays of Jo's patient's arm, but Jo is worried she broke it. Callie assures her the tetanus spasm was strong enough to have done it. But they're going to have to break it again to get the arm to heal.

April tells Bailey she wants to be able to help Jackson, but Bailey tells him it's good that Jackson wants to handle it on his own. They see that Braden's abscess is spreading to his brain. They have to call Derek.

Derek is practicing his speech and a nurse comes to tell him he's needed.

Ivy's dad -- who had stayed home with their other daughter because she'd gotten the flu that's been going around -- has brought the other daughter, Frankie, to the hospital because she was getting worse. Hunt comes and says Frankie has cardio myopathy, the same as Ivy. Frankie crashes and Hunt has to tend to her.

Cristina reports to Ivy's parents that her transplant went well, but Frankie's going to need a pacemaker. Cristina and Hunt decide to look into the extreme coincidence that two siblings would have cardio myopathy at the same time.

Shane, worried that he's picking up the virus even though his temperature is fine, asks Stephanie to watch the conduit kids. She does, but only after he offers to take weekend calls for her for a month.

Alex and Jo are arguing about his ability to pay off his student loans and Jo is upset. Callie walks in and tells Jo she's going to need that aggression to break her patient's arm again.

Afterward, Alex agrees with Arizona that Dr. Lebackes is very good, but Alex is still annoyed with the surgeon's exuberant and not-terribly-humble approach. Dr. Lebackes asks Alex if he plays golf because it's time to "unwind."

Derek comes to Bailey and April's O.R. to see Braden, but they stop him when they see that Derek looks sick. They try to think of an alternative to Derek.

We next see Webber in surgery, where Leah has connected herself to an I.V. to stay hydrated. Webber says he's "proud" of her.

Derek, meanwhile, has put on a big hood and mask to avoid spreading his germs.

Callie asks Jo to use a hammer to complete the break of her patient's arm. Jo is hesitant, explaining that she doesn't know her own strength. Jo does it, and next, "We drill," Callie says.

Derek is taking his surgery slowly, because he's about to puke.

Alex and Dr. Lebackes are playing a golf video game in Lebackes' office. He has a private practice and offers Alex a spot there as he and his partners are looking to expand. He tells Alex the buy-in is $250,000, which he'll pay off in two years, and he'll pay off his student loans in another two. Alex is intrigued.

Webber and Meredith are asking Leah to suction fecal matter and pus, and she throws up in her mouth. They send her home, then call her a "lightweight" and a "wuss."

Stephanie is watching the conduit kids, getting peed on while changing their diapers.

Abraham, the brother of Logan, Jo's patient, thinks it's funny that Logan -- who rejects all things unnatural -- has a titanium rod in his arm. Afterward, Callie notices that Jo has "the ortho glow."

Alex comes to the hospital and asks Arizona how much she makes as an attending at the hospital. She refuses to answer.

Derek can barely stand, but his speech is about to start. Meredith tells him he needs to call the speech off. He starts to walk down the hall, but collapses.

We next see Derek in a hospital bed trying to get up. A nurse forces him to stay in bed.

Callie is talking to Arizona through the bathroom door, rather dreamily talking about how Jo seems suited to orthopedics.

Braden wakes up alone in his room, with blurry vision, and his parents and Bailey are outside in the hallway looking through the window. His parents tell him they love him.

April gets home and hears Jackson throwing up. He insists he doesn't want help. She tells him she's there if he needs anything.

Alex, back home, argues with Jo again about his finances. She insists that he needs to pay his bills. He tells her he may have figured out a way to take care of all of it.

Meredith comes to Derek's room and reports to him that the scientists from around the world were sold on his project. She gave the speech, which she'd said she'd heard so many times she could do it herself.

Cristina and Hunt tell Ivy and Frankie's parents they haven't figured out a cause for their daughters' problem. But they caught it and are treating it. Suddenly, their younger son starts coughing, but he's coughing up the same stuff his sister had earlier.