New York and New Jersey will tighten Ebola screenings at airports after a doctor who recently returned to the U.S. from West Africa tested positive for the virus. Anyone arriving in either state who is considered at “high risk” of having Ebola will be automatically quarantined for three weeks, the governors of both states announced at a news conference Friday.

“A voluntary Ebola quarantine is not enough,” New York Gov. Andrew Cuomo said at a press conference Friday. “This is too serious a public health situation.”

Travelers entering the U.S. after having contact with Ebola patients will be rerouted to either John F. Kennedy International Airport or Newark Liberty International Airport, according to the New York Times. Once off the aircraft, travelers will be extensively interviewed about their time in countries hardest hit by the disease such as Guinea, Liberia and Sierra Leone.

Ebola is not contagious unless the person is symptomatic and, even then, can only be contracted through coming in contact with their bodily fluids. As a precaution, travelers who have recently gone to countries where the disease is rampant or who have had contact with Ebola patients were urged to quarantine themselves for the length of the incubation period upon their return to the U.S.

After the fourth case of Ebola in the U.S. was confirmed Thursday, however, New York and New Jersey officials don't want to leave anything to chance.

“There is no more ‘voluntary quarantine’ in New Jersey because you can't count on people to do it,” said New Jersey Gov. Chris Christie.

Craig Spencer, the doctor now infected with Ebola, came in contact with four people in the U.S after he returned from a Doctors Without Borders trip to Guinea. He was immediately put in isolation Thursday at Bellevue Hospital when he started showing symptoms, but that was only after he traveled from Manhattan to Brooklyn using the subway Wednesday night, according to the New York Times. He went to a bowling alley in Williamsburg and then took the car service Uber back to his apartment in upper Manhattan.

The additional precautions at airports are a striking change in tone from the New York officials’ press conference Thursday night, where Cuomo and Mayor Bill de Blasio both said New Yorkers had no reason to panic.

Cuomo said the state had been preparing for a possible Ebola case for months and is “as ready as one could be for this circumstance.”