Two Dallas city spraygrounds have been closed temporarily after children became ill with symptoms associated with the parasitic infection cryptosporidiosis.

Spraygrounds at Mildred Dunn Park on Reed Lane in South Dallas and Campbell Green Park on Parkhill Drive in Far North Dallas were closed Friday. They are scheduled to reopen Sunday.

One child who played at the Dunn sprayground in mid-July has tested positive for the illness, Dallas County Health and Human Services director Zachary Thompson confirmed Friday. About five other children in the same daycare group also became ill, but those cases have not been confirmed.

A child who played at Campbell Green, also in mid-July, showed symptoms, but the illness has not been confirmed.

The closures come on the heels of an outbreak of the infection linked to a Fort Worth lake that sickened at least 20 people. Burger's Lake is set to reopen as early as this morning.

Mr. Thompson said the health department is recommending that the city look at its other spraygrounds, which he says are high-risk settings for the parasite, which is usually spread through fecal matter.

"We don't know how often they change the water" at the Mildred Dunn sprayground, Mr. Thomspon said.

Dallas Parks Director Paul Dyer said water in the spraygrounds is constantly recycled. He said the city shut down the spraygrounds as a precaution. When illnesses are linked to parks, they are immediately closed and treated. He said the city has no plans to shut down and treat all spraygrounds without reports of illnesses.

Burger's Lake, the private West Fort Worth lake linked to an outbreak of cryptosporidiosis, plans to reopen today. But a worker there said Friday that it still has to get approval from the county health department, and that might not happen before the planned 9 a.m. opening.

The outgoing phone message at Burger's Lake on Friday morning said: "We have completed the hyperchlorination process required by the ... [Centers for Disease Control and Prevention] and the local health department."

That afternoon, Kay Thomas, who said she was just answering the phones for the park, said the chemical levels haven't dropped enough yet to be inspected.

"We're not real sure we're going to be able to make it tomorrow if we don't get that chlorination down to a normal level," she said.

The high chlorine concentration was needed to eliminate Cryptosporidium, which was found in water samples. The water at Burger's Lake is filtered and chlorinated, but crypto, as it's frequently called, is resistant to the chemical at levels found in swimming pools.

Ms. Thomas said a county health inspector would be on call until 10 p.m. Friday to verify the chlorine level. She said he would also be willing to go to the park this morning to check the water if needed.

The chlorine level at Burger's Lake started dropping about 4:30 p.m., Ms. Thomas said.

The federal CDC notified Tarrant County Public Health on Wednesday that the water samples from the lake tested positive for Cryptosporidium. County officials also tested the well water that serves as the source water for the lake and didn't find any fecal matter, which is the way Cryptosporidium is usually spread.

There have been 20 confirmed cases of cryptosporidiosis, but that number could increase significantly. The health department has received phone calls from 700 people who said they had been at Burger's Lake since late June, when the first infection probably occurred. About 600 of those callers told investigators that they had suffered from diarrhea, although county officials said it's not clear how many of those had cryptosporidiosis.

The people with symptoms of an infection, which also includes stomach cramps, vomiting and dehydration, were told to go to their doctors and get tested. The law requires that cryptosporidiosis be reported to the local health department.

The county averaged six cases annually in 2006 and 2007. There were seven cases between January and June of this year, but it wasn't clear whether any of those were also part of the 20 confirmed cases in this current outbreak.

•This contagious diarrheal disease is caused by a microscopic parasite called Cryptosporidium that can live in the intestine of humans and animals and is passed in the stool of an infected person or animal.

•Cryptosporidium is chlorine-resistant and can live for days in chlorine-treated water.

•People generally get sick two to 10 days after becoming infected with the parasite.

•Symptoms include watery diarrhea, stomach cramps or pain, dehydration, nausea, vomiting, fever and weight loss.

•Illness usually lasts one to two weeks, but symptoms can come and go for as long as 30 days.

•People with cryptosporidiosis can contaminate recreational swimming areas for several weeks after symptoms have ended. Immersion in the water may be enough for contamination to occur.

•People with weakened immune systems may develop a serious, sometimes fatal illness and should seek medical care.