Tzeka fever is a disease that afflicts Cardassians. It is not usually fatal, althought it can be if not treated with the proper medicine. It can be removed from water systems by filters.
In 2376, an outbreak of tzeka fever began in Cardassia City. The government deployed medics and announced the outbreak had been contained, although the announcement of tzeka fever was the spark that set off long-awaited riots in the capital. (DS9 novel: Cardassia: The Lotus Flower)