HOUSTON (AP) — Health officials are trying to find passengers from four Southwest Airlines flights last month who might have been exposed to measles.

The travelers shared flights on Aug. 21 and Aug. 22 with someone from North Texas who was later diagnosed with the highly contagious virus. The flights went to Dallas, Houston and Harlingen.

The Houston Health Department says it's helping to find the passengers who might have been exposed to the virus.

The health department says that passengers exposed to this patient might develop symptoms as late as Sept. 12.

Symptoms include rash, high fever, cough, runny nose and red, watery eyes

This investigation is being coordinated by the Texas Department of State Health Services.