[Hospital infection: seven years of systematic research at a general hospital in São Paulo].

A seven year analysis with established adequate methods of reporting and confirming hospital acquired infections shows a surprising statistically significant relationship between the frequency of hospital acquired infections and the number of infected patients admitted to this hospital: hospital acquired infections comprised 2% to 3.7% of all admissions, and patients already infected admitted were 5.3% to 8.4%. Surgical wound infections were the most frequent acquired infections. Followed by respiratory infections and urinary tract infections. During the 7 years period there was a very pronounced drop in the number of cases with infectious diseases acquired inside the hospital and a fall in infections acquired after cardiac surgery.