RESUMEN
Fly sampling was evaluated under laboratory conditions before starting the field surveys. Three different fly traps were tested, of which the Spiralettes [a commercial one] proved to be the most efficient. Sampling conditions were also considered in this laboratory evaluation, light, air current, swinging, height and temperature were tested, all of them have affected fly trapping except height. Fly density and distribution in two general hospitals and two specialized ones, were estimated in order to evaluate them epidemiologically in relation to hospital bacterial contamination. Results of these surveyes revealed the followings [I] The location of the hospital has no impact on the fly density. [2] Flies are attracted more to swinging hanged ribbon traps than to fixed ones. [3] Fly densities were relatively high in the main kitchens and the main garbages followed by toilets [common ones], patient wards, outpatients investigating rooms, surgical theaters and plasterrooms of the hospitals. [4] Fly density is higher during warm seasons than in cold ones