shokrollah salmanzadeh health research institute, infectious and tropical diseases research center, ahvaz jundishapur university of medical sciences, ahvaz, ir iran; razi teaching hospital, clinical research development center, ahvaz jundishapur university of medical sciences, ahvaz, ir iran farid yousefi health research institute, infectious and tropical diseases research center, ahvaz jundishapur university of medical sciences, ahvaz, ir iran; razi teaching hospital, clinical research development center, ahvaz jundishapur university of medical sciences, ahvaz, ir iran fatemeh ahmadi health research institute, infectious and tropical diseases research center, ahvaz jundishapur university of medical sciences, ahvaz, ir iran sahar geravandi razi teaching hospital, clinical research development center, ahvaz jundishapur university of medical sciences, ahvaz, ir iran; tehran medical sciences branch, islamic azad university, tehran, ir iran moghgan moien razi teaching hospital, clinical research development center, ahvaz jundishapur university of medical sciences, ahvaz, ir iran mohammad javad mohammadi razi teaching hospital, clinical research development center, ahvaz jundishapur university of medical sciences, ahvaz, ir iran; department of environmental health engineering, school of public health, ahvaz jundishapur university of medical sciences, ahvaz, ir iran; department of environmental health engineering, school of public health, ahvaz jundishapur university of medical sciences, ahvaz, ir iran. tel: +98-9355439707, fax: +98-6133336513