A study made in China by Leyer in 2009, showed that daily supplementation with probiotics is useful in preventing respiratory virus diseases during winter in healthy small children. The probiotics inhibit the adherence of pathogenic enterobacteria (E. coli) which considerably reduces the number of cells containing immunoglobulin A. The places of adhesion for lactobacilli and E coli are not the same and the exact mechanism of action is referring either to the direct control of microorganisms, either to the indirect action by stimulating the indigenous micro-flora and their metabolism. Immediately after birth, there can be implemented types belonging to the indigenous normal micro-flora.