A telephone message left on Tuesday night for the Hernandez family was not returned.
The episode did not prompt any specific changes to the airline’s safety protocols, which Mr. Hobart noted had long been in place. Officials also said that the finding that Mr. Hernandez had Covid-19 had not changed the precautions that were already being taken after the flight.
Taylor Garland, a spokeswoman for the union that represents flight attendants, said in a statement last week that four flight attendants who had been on Flight 591 had been in quarantine since landing in Los Angeles.
Mr. Hobart said on Tuesday that United had provided information last week to the Centers for Disease Control and Prevention about who was on Flight 591 for the purposes of contact tracing. “Per the federal guidelines, the C.D.C. then reaches out to customers that they believe may potentially have been at risk for infection,” Mr. Hobart said.
An email message to the C.D.C. on Tuesday night was not immediately returned.
On Tuesday night, two people who said they had been on the flight and had rendered aid to Mr. Hernandez said they had not been contacted by health officials.
Jacquelyn Tran and her boyfriend, Steven Chang, both 29, of Orange County, Calif., said in interviews that they had been sitting across the aisle and one row behind Mr. Hernandez during the flight. Ms. Tran said she had seen Mr. Hernandez “trying to get out of his seat” about 20 minutes after takeoff and asked a flight attendant to check on him.
Eventually, several passengers and flight attendants rendered aid to Mr. Hernandez for the duration of the flight, the couple said. They included Mr. Chang, a medical student; Ms. Tran, an administrative assistant at a cancer center; a nurse who was seated in the back of the plane; an emergency medical technician who was seated toward the front of the plane; and several flight attendants.
Ms. Tran administered epinephrine, which can reduce swelling in the airway and increase blood flow in the veins, and also helped provide intravenous fluids to Mr. Hernandez, she said. Mr. Chang and the nurse provided cardiopulmonary resuscitation to Mr. Hernandez, the couple said.