The second Dallas healthcare worker to be diagnosed with Ebola flew on Oct. 13, the day before she reported symptoms.

The Centers for Disease Control and Prevention are asking all passengers on that flight to call the agency.

According to the flight's crew, the healthcare worker, 29-year-old Amber Jay Vinson, showed no signs or symptoms of illness while on Frontier Airlines Flight 1143 from Cleveland to Dallas-Fort Worth. She was reportedly in Akron to visit family, according to the Ohio Department of Health.

The plane that may have carried the virus is being held and cleaned at Cleveland Hopkins International Airport, ABC 5 reports.

Little Risk Of Spreading

Because Vinson wasn't showing any symptoms of Ebola while on board the flight, it is very unlikely she could have infected other passengers.

The CDC is taking extra precautions in this case because Ebola is such a severe virus. If Vinson had been symptomatic on the flight — if she'd had a fever, for example — she could have transferred Ebola to someone else only through direct contact.

That means another passenger or flight crew would have had to touch Vinson's saliva, feces, urine, or blood and then touched their eyes, mouth, or an open cut or wound.

"The fact that the patient number two did not have a fever until the next day, did not have nausea or vomiting on the plane, suggests to us that the risk to any individual on that plane would be very low...we'll always put in extra margins of safety," said CDC Director Tom Frieden on a call with reporters on Wednesday.

The Ohio Department of Health also released a statement saying the state "has swiftly acted and is working with the CDC and Summit County health officials to identify people who may have been in close contact with the health care worker and implement quarantine as necessary."

Plane Being Cleaned

The plane Vinson flew on remained at the airport overnight on Monday and was thoroughly cleaned using the airline's normal procedures before it returned to service the next day, Frontier said in a statement. The plane was cleaned again in Cleveland on Tuesday night and will be used for a flight to Dallas on Wednesday evening.

On Oct. 10, Vinson flew from Dallas-Fort Worth to Cleveland on Frontier flight 1142, according to the airline.

"After 1 p.m. ET, public health professionals will begin interviewing passengers about the flight, answering their questions, and arranging follow up," the CDC said in a statement. "Individuals who are determined to be at any potential risk will be actively monitored."

More Ebola Cases Expected In Dallas

More than 4,000 people have died in this year's Ebola outbreak, mostly in Guinea, Liberia, and Sierra Leone. More than 8,000 have the virus.

Vinson is the second nurse to be diagnosed with Ebola in the US. Both nurses diagnosed this week work at Texas Health Presbyterian Hospital in Dallas and cared for Thomas Eric Duncan, who contracted Ebola in Liberia and flew to the US for a visit before he started showing symptoms. Duncan died last week.

Dallas officials have said that more Ebola cases in the area are a "very real possibility," but there is still very little risk of an outbreak in the US. Healthcare workers are especially vulnerable because they come into contact with the bodily fluids of infected patients.

Nurses who helped care for Duncan allege that they didn't have the proper protective gear and had to deal with constantly changing protocol from the hospital.

Vinson is now in isolation at Texas Health Presbyterian. Other healthcare workers who came into contact with Duncan are self-monitoring for symptoms and have been told to report to the hospital if they develop a fever or start feeling ill.

The common areas in Vinson's apartment complex are being decontaminated and her neighbors have been notified.

Ebola often begins with flu-like symptoms and a fever and can progress to internal and external bleeding and organ failure.