STANISLAUS COUNTY (CBS13) — Health officials in Stanislaus County want the water tested at a popular swimming hole and reservoir that supplies drinking water after a man says he became deathly ill after swimming there.

Luis Lopez told CBS13 on Monday that he became very ill after swimming at the Woodward Reservoir in Oakdale. He says his fever spiked to 107 degrees and he felt like “a zombie.” He says hospital officials told him a waterborne bacteria was likely the cause.

READ MORE: Hiker Captures Moment She Thought She Might Die on Video, Before Search Crews Rescue Her

On Tuesday, CBS13 spent the day searching for answers as to why tests hadn’t been done on the water.

Health officials aren’t 100 percent sure how Lopez got sick. One of them is stressing there is no cause for alarm, and no public health risk.

But some swimmers like Oswaldo Cruz aren’t taking any chances. He pulled his grandson out of the waters of Woodward Reservoir once he heard about Lopez’s illness.

“They should’ve stopped people from coming into the park because it’s bad,” he said.

Lopez says he lost 28 pounds in a week from his illness after swimming at the reservoir.

But not everyone is so sure the bacteria came from the reservoir.

“It’s very difficult to isolate the source or cause of this particular bacteria,” said Troylene Sayler with the South San Joaquin Irrigation District.

She says the bacteria, campylobacter is found in nearly every body of water and also in raw poultry.

READ MORE: Barrage Of Bullets That Hit Stockton Homes Caught On Video

“I think it’s an isolated incident and we certainly would not want the public to panic,” Sayler said.

CBS13 asked the irrigation district about the drinking water it supplies from the reservoir to Manteca, Tracy and Lathrop.

They say any harmful bacteria is removed at the treatment plant before it could get to homes or businesses.

“That’s because we assume there are contaminants in the water bacteria all of that we chlorinate the water for that purpose,” Sayler said.

The reservoir water that people like Lopez swim in is another matter.

“We have tested the water there; in fact, we tested it as late as last week,” she said.

Those tests revealed higher than normal bacteria. Several posted signs warn to swim at your own risk.

But the district says those levels weren’t high enough to pose a threat and force the reservoir to close. In any case, that decision is up to Stanislaus County Environmental Health and they’ve kept it open to the public.

MORE NEWS: Diver Recovers Lost Wedding Ring From American River, Reunites It With Heartbroken Husband

The department wants the irrigation district to move up its regularly scheduled testing. Meanwhile the irrigation district told CBS13 they referred environmental health to a lab that could do the testing for them.