A passenger traveling on a Southwest Airlines flight may have exposed other people to measles, authorities have warned.

Santa Clara County health officials have notified the public that an adult—whose identity was not disclosed for privacy reasons—flew from California to Chicago after contracting the infectious disease.

Flight WN 2904 departed on July 2 at 5:15 a.m. from San Jose Mineta Airport (SJC) and landed at Chicago Midway International Airport at 7:30 a.m.

Dozens of travelers and employees have been warned of possible exposure and advised to monitor any potential symptoms, which develop at around 10 days after infection.

Initial signs of the illness include flu-like traits, such as a runny nose and high fever, light sensitivity, and white spots on the inside of the person's cheeks. This escalates into a distinctive red, blotchy rash that is highly infectious to those that haven't been vaccinated. Untreated measles can lead to neurological or respiratory complications and, ultimately, death.

Travelers check in at Southwest Airlines at Hartsfield-Jackson Atlanta International Airport on June 28, 2024 in Atlanta, Georgia. The airline has informed all passengers and staff of potential exposure to the highly contagious disease. Travelers check in at Southwest Airlines at Hartsfield-Jackson Atlanta International Airport on June 28, 2024 in Atlanta, Georgia. The airline has informed all passengers and staff of potential exposure to the highly contagious disease. Kevin Dietsch/Getty Images

Airport representatives confirmed they weren't made aware of the travel hazard by the Santa Clara Public Health Department until July 8.

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"We immediately notified our employee and partners working at SJC, as well as the public, through media outlets and our social media channels," a spokesperson told Newsweek. "The health and safety of our passengers and employees are of utmost importance to SJC. We are coordinating closely with the County of Santa Clara Public Health Department to take all necessary precautions."

The passenger is not believed to be a California local. Authorities have been informed that they visited a local Starbucks on Blossom Hill Road, Los Gatos and Taqueria Los Pericos in Santa Cruz on July 1, the day prior to their flight. Customers who recall visiting these locations on that day have also been advised to keep an eye on any symptoms.

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"The safety of our partners (employees) and customers is always our top priority. There is no evidence that any other customers or partners were affected. We're working closely with Santa Clara Public Health Department and continuing to monitor for symptoms," a representative for Starbucks told Newsweek.

Illustration photo of a vaccine syringe in hand, shot in Savigny sur Orge, France on April 20, 2024. Global vaccination rates for measles are at their lowest since 2008. Illustration photo of a vaccine syringe in hand, shot in Savigny sur Orge, France on April 20, 2024. Global vaccination rates for measles are at their lowest since 2008. Daniel Dorko/Hans Lucas/AFP via Getty Images

Measles can affect anyone, but tends to appear more often in children. At the turn of the millennium it was deemed eliminated from the U.S., due to year-on-year vaccine rates regularly topping 90 percent, until 2018, when the CDC declared an outbreak in New Jersey. World Health Organization estimates suggested over 136,000 people died from the disease globally in 2022, though this is more common in territories with lower vaccine rates. The percentage of vaccinated children is at its lowest since 2008.

"Measles is highly contagious and spreads through the air when someone with measles speaks, coughs, or sneezes. It is very easy for anyone close to the individual to become infected," said Dr. Monika Roy, Communicable Disease Controller and Assistant Health Officer at County of Santa Clara Public Health Department in a statement.

"Call your doctor right away if you think you may have been exposed. Quick action can prevent many more people from becoming sick with this serious disease."

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