Hospital officials said children are likely spreading the bacteria while in close contact at summer camps or in swimming pools.
The total number of cases seen at Cook Children's this year is much higher than any of the previous five years, with up to 100 cases in late June. None of the previous five years saw the number of cases rise above 20. While mycoplasma pneumonia is typically seen in children under the age of 6, cases this summer have been identified in every age group, the hospital said, from infants to adolescents.
"While a lot of bacterial infections can be very invasive and very obvious you're sick quite quickly, mycoplasma can actually start very slowly and live inside your body with not a lot of inflammation at first," Rister said.