Passengers on four Southwest Airlines flights in Texas may have been exposed to measles in the last 16 days. The flights were between Dallas, Houston and Harlingen.

The airline said it has contacted the passengers who traveled on the flights, of which one was later diagnosed to have contracted the illness. According to a Southwest Airlines spokesman, the airline will not release any information regarding the traveler who might have spread the disease.

“Our safety and security groups worked with the CDC (Centers for Disease Control and Prevention) to support the agency’s work in reaching our customers who traveled onboard four intra-Texas flights last week with a passenger later diagnosed with measles,” a statement from Southwest Airlines said. 

“We’ve shared awareness of the situation and protocols with our employees who also were onboard these aircraft,” the statement said.

The passenger later diagnosed with measles flew on the following flights:

  • Flight No. 5, between Dallas and Houston on Aug. 21, 2018
  • Flight No. 9, between Houston and Harlingen on Aug. 21, 2018
  • Flight No. 665, between Harlingen and Houston on Aug. 22, 2018
  • Flight No. 44, between Houston and Dallas on Aug. 22, 2018

Health departments in Dallas, Houston and Harlingen reached out to the passengers, via letters, warning of the infection. According to the CDC, if one person has measles, 90 percent of the people close to that person who are not immune will also become infected.

However, a doctor told local media that people at the airport are at a much lower risk of exposure for the virus than those passengers who shared the plane with the patient.

"That's why our focus is on directly contacting the passengers to notify them of the risk, inquire about their vaccination status, and make sure they monitor for symptoms and seek medical attention if necessary," Dr. David Persse said.

The symptoms of measles always include fever and at least one of the three Cs: cough, coryza, or runny nose, conjunctivitis. Other symptoms include dry hacking cough, watery eyes, photophobia, or sensitivity to light, sneezing, a reddish-brown rash and body aches.

Symptoms will appear about 9 to 11 days after initial infection.

The health department said Thursday that passengers exposed to the patient may develop symptoms as late as Sept. 12.

Complications of a measles infection can include, diarrhea, vomiting, eye infection, respiratory tract infections, such as laryngitis and bronchitis, difficulty breathing, ear infections -- which can lead to permanent hearing loss and febrile seizures.

A passenger who received a letter from the Dallas health department told NBC 5 Investigates that she is now concerned about some symptoms she has.

"Mostly, like I said, rash appeared on my legs. I did speak to the health department and explained my symptoms, so their advice was to go to the doctor. They didn't think that it may or may not be measles but they advised me to visit my physician," Monica Nicholas said.