Dallas County health officials have identified another case of cyclosporiasis.
The total number of cyclospora cases in Dallas County is now 38. Dallas, Tarrant, Denton and Collin counties report a total of 128 cases.
More than 600 people in 23 states, including 282 people in Texas, have been sickened by the microscopic parasite this summer, according to the Centers for Disease Control and Prevention.
The CDC says that early evidence shows that the cases in Texas are not linked to the illnesses in other states.
The source of the outbreaks in Iowa and Nebraska was linked to a salad mix served at restaurant chains in those states, but the cause in other states has not been determined.
The source of the salad mix in Iowa and Nebraska, Taylor Farms de Mexico, suspended production and distribution of the mixes on Aug. 12 until it was given the all-clear by the Food and Drug Administration on Aug. 25.
In the Texas outbreak, health officials are doing a lot of retracing of footsteps, said Dr. Cedric Spak at Baylor University Medical Center.
"They have to follow the path, so it does sometimes almost seem like something you'd see on a television show -- so, boots on the ground," he said. "They have to travel. They have to go place to place to figure it out."
In some previous cyclospora outbreaks, the cause was never discovered, federal officials say.
Thorough washing of produce is recommended, however, it may not eliminate the risk of cyclospora transmission, according to the Dallas County health department.