A number of recreational water illness outbreaks were reported during summer 2011, and experts say that record hot weather — including a July heat wave which hit 23 states — may mean a larger number of cases this year.

Additionally, a new study indicates there’s a greater likelihood of developing a gastrointestinal illness after a dip in a public swimming pool.

One of the largest outbreaks of 2011 was in the Cincinnati/ Northern Kentucky area. Health officials confirmed more than 250 cases of crypto, along with a larger-than-normal number of Shigella cases (nearly 130). More than a dozen pools were superchlorinated.

“Historically, we have seen outbreaks,” said Emily Gresham Wherle, public information administrator at the Northern Kentucky Health Department. “This year, we have taken a more aggressive approach to try and curb the spread of the illnesses, and hope to see some success in that.”

In the Kansas City area, the Missouri Department of Health and Senior Services reported an 88.5 percent increase over the median number of crypto cases in the past five years. An August outbreak of at least 80 confirmed cases prompted officials to ask pool operators to close for the season early. Several did shut down ahead of schedule, and season-end events were canceled.

Other crypto outbreaks occurred in Temple, Texas, where at least a dozen cases were reported; in the Pueblo, Colo., area, where at least 15 cases were confirmed, stemming from Wild Waters Park in Walsenburg, about 50 miles outside Pueblo; and Lafayette County, Mo., where there were at least seven confirmed cases connected to the Lexington Water Park.

Operators voluntarily superchlorinated, but “there were no certified pool operators on site and no disinfection logs,” noted Tom Emerson, Lafayette County Health Department environmental public health specialist. He is planning to push for a law that would require certified operators on site.

Crypto and Shigella weren’t the only threats this summer. In June, six children were hospitalized with E. coli o157 after visiting the Opelika (Ala.) SportsPlex and Aquatic Center.

Anyone who experienced an RWI this summer knows all too well what researchers in Melbourne, Australia, have learned. In a study published in the American Journal of Epidemiology, they found that among a cohort group of about 2,800, the risk of gastroenteritis went up about 25 percent after a pool visit.

Here in the United States, preliminary outbreak statistics for 2011 will be available next year, said Michele Hlavsa, chief of the Centers for Disease Control and Prevention’s Healthy Swimming Program. Nonweather factors that could impact final numbers include greater awareness among health officials and the public, and streamlined reporting methods.