Hantavirus live updates: Risk to general public 'very, very low'

The Department of Health and Human Services released a statement on Sunday saying one American has tested positive for hantavirus as the plane with 18 MV Hondius passengers is headed to the U.S.

Two of the passengers on the plane are traveling in the aircraft's biocontainment units "out of an abundance of caution," according to HHS.

The agency said that of the two, one passenger currently has mild symptoms, and the other has tested PCR positive for the virus.

The plane is first going to the ASPR Regional Emerging Special Pathogen Treatment Center (RESPTC) at the University of Nebraska Medical Center before taking the passenger with mild symptoms to a second RESPTC, according to HHS.

"Upon arrival at each facility, each individual will undergo clinical assessment and receive appropriate care and support based on their condition," HHS said.

The plane carrying the 18 Americans who disembarked from the MV Hondius has departed Spain and is heading back to the United States.

The American passengers who disembarked from the MV Hondius have arrived at Tenerife airport in the Canary Islands.

A total 18 people will be on the American repatriation flight, including the 17 Americans and one British national who is a resident of the U.S., the Spanish minister of health told ABC News.

-ABC News' Maggie Rulli

The 17 Americans aboard the MV Hondius have begun disembarking from the ship.

As of Saturday, none of the American passengers had tested positive for the hantavirus, according to the Centers for Disease Control and Prevention (CDC).

The aircraft that will return the Americans to the U.S. is expected to take off from Tenerife at 9:30 p.m. local time/4:30 p.m. Eastern time but could possibly depart earlier if circumstances allow, a source with the Spanish president's office previously told ABC News. It is not yet clear if or when that aircraft has landed in Tenerife.

The passengers will be flown to the National Quarantine Unit in Omaha, Nebraska, managed by Nebraska Medicine and the University of Nebraska Medical Center and the only federally funded quarantine unit in the U.S.

During a press briefing Friday, officials with the National Quarantine Unit said there is not yet a defined period for how long the passengers would remain at the unit.

-ABC News' Dragana Jovanovic, Aicha El Hammar and Maggie Rulli