Since the construction of the Aswan Dam, several million more Egyptians have become infected with bilharzia, a debilitating disease already causing an economic loss to the country of about US $ 560 million a year.
這筆帳為什麼算到水壩上？原來，性喜潮濕的蝸牛是血絲蟲的中間寄主，每逢雨季，血絲蟲就搭蝸牛便車，四處傳染；到了尼羅河旱季，蝸牛缺水無法生存，數量劇減，血絲蟲也自然收歛。