En el verano de 2000, se evidenciaron en EE.UU. cinco brotes de esta enfermedad que comprometieron a aproximadamente 1000 personas.
En Ohio, se identificaron 700 casos sospechosos y se realizó un estudio de caso control mediante el cual se asoció el nadar en cierto club privado con el riesgo de padecer la enfermedad.
En los últimos años, se evidenció un aumento de los brotes de enfermedad gastrointestinal relacionado con piletas de natación. Esto se debe a que los quistes de Cryptosporidium son resistentes al cloro, y pueden ser infectivos durante días en agua de pileta de natación aunque estas contengan las concentraciones recomendadas de cloro. Además, por su tamaño pequeño no pueden ser removidos por los filtros.
Teniendo en cuenta los altos títulos de Cryptosporidium en la materia fecal de los infectados y la baja dosis infectiva, la contaminación de la pileta es factible y la ingestión accidental de pequeñas cantidades de agua pueden resultar en infección.
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