An upswing in cholera in Haiti has prompted health care workers and aid agencies to step up efforts to prevent the water-borne disease from spreading as the rainy season begins. Those most at risk are the 500,000 people who remain in often shabby settlements where thousands took shelter after a January 2010 earthquake devastated Haiti. Catholic Relief Services was among the aid agencies that boosted the distribution of soap, water purification tablets and hygiene information within 24 hours of the initial spike in early April following a period of heavy rain. C.R.S. reported reaching 22,000 families within days; in Port-au-Prince, agency workers installed or repaired sanitation stations in 12 settlements. There was no cholera in Haiti until the arrival of U.N. troops after the earthquake. Investigators traced the outbreak to faulty equipment at a camp of Nepalese soldiers. More than 7,050 people have died, and more than 532,000 people have contracted the disease.