Tarrant County health officials have now confirmed 16 cases of cryptosporidiosis and the city of Arlington will closes its pools today while they are hyperchlorinated, a treatment that can kill the water-borne parasite. If ingested, cryptosporidiosis, or "crypto," can sicken people for up to two weeks with stomach cramps and diarrhea.
The "common thread" linking the cases still appears to be Burger's Lake, a popular Fort Worth swimming hole, though the lake still hasn't been confirmed as the source, said Vanassa Joseph, a spokeswoman for Tarrant County Public Health.
Public health officials told cities that they must hyperchlorinate their pools, and the treatment was recommended for all public pools, including those operated by apartment complexes and neighborhood associations.
Officials have said they are concerned the parasite could spread further by infected people swimming in other pools.
Fort Worth treated its pools over the weekend, as did the water park NRH20, officials said. Arlington will treat its pools Wednesday.
"We are following the health department's recommendations as a matter of precaution," said Bill Gilmore, Arlington parks and recreation assistant director. "Hopefully most people understand this is for their safety."
Arlington pools are scheduled to reopen Thursday.
The number of confirmed cases of crypto has risen from nine on Friday.
The Centers for Disease Control and Prevention is conducting tests to determine whether the parasite was in the water at Burger's Lake, Joseph said. However, fecal contamination was not found in the water used to fill the lake during tests in local laboratories.
Crypto is found in human and animal fecal matter. It thrives in bodies of water.
The owner of Burger's Lake voluntarily closed the lake last week as a precaution.
"There is a series of tests being done and, when they are all completed, we hope to have more conclusive results," Joseph said. "Until the tests are completed, we just aren't going to know."
A CDC spokeswoman said Tuesday she did not know how long it would take to complete the tests.
Health officials this weekend recommended hyperchlorination for all area public pools in Tarrant, Dallas, Collin and Denton counties. That means for a short time increasing the amount of chlorine added to the water to about 20 or 30 parts per million. No swimming is allowed during that period, usually about 12 hours, officials said.
The parasite has not been found in any Arlington public pools, which are inspected for health and safety risks regularly, park officials said Tuesday.
But the pools will close Wednesday for the treatment and reopen Thursday.
Fort Worth treated its pools overnight Sunday and Monday when the pools are closed anyway, said Amy Casas, a spokeswoman for the Fort Worth Public Health Department. The pools reopened Tuesday.
The water park in North Richland Hills treated its water overnight Friday, said Elizabeth Copeland, a marketing specialist for the park. The process slightly delayed the park's opening Saturday morning.
One more hospitalized
The number of people hospitalized by their symptoms has risen from two to three, Joseph said. Two of those people are now recovering at home and Joseph was unsure of the condition of the third. Symptoms of cryptosporidiosis include diarrhea, nausea, loss of appetite, vomiting and dehydration. The symptoms may last two weeks.
Outbreak announced Thursday
Tarrant County Health officials announced Thursday that eight people had been diagnosed with crypto and that Burger's Lake, a one-acre spring-fed lake, was possibly the source. Anyone who visited the lake after June 21 and became ill was encouraged to seek medical care.
Staff writer Susan Schrock contributed to this report.