Text Box: SEROPREVALENCE OF PARVOVIRUS B19 ANTIBODIES CHILDREN 1 MONTH TO 18 YEARS AT THE NATIONAL INSTITUTE OF PEDIATRICS Mercedes Macias, Napoleon Gonzalez, Uciel Ochoa, Miguel Rodriguez National Institute of Pediatrics, Mexico City. Objective. The aim of this study was to determine the seroprevalence of parvovirus B19 (PVB19) antibodies in healthy children from one month to 18 years of age attending at the National Institute of Pediatrics in Mexico city, stratified by age and compared with crowding and hygiene background. Material and Methods. A prospective transversal and comparative study was done in children attending at outpatient clinic for blood samples from August 1997 to January 1998. To render a representative sample patients were selected at random from the total sample and this subjectes were interviewed for crowding and hygiene living conditions. Written informed conscent by parents were obtained in all cases. Serum saples were obtained for specific IgG antibodies against PVB19 by immunofluorescence test (Biotrin International). Analysis Data. Risk ratio and interval confidence 95% was done by Pearson x2 and x2 corrected by Yates with statistical significance of p<0.05. Results 99 patients were included for analysis, 50 were females, aged between 1 to 216 months with an average age of 76.6+54.5 months. The overall seroprevalence was 45.5%, with 28.2% seropositivity in children less than 5 years of age, 76 (76.8%) lived in crowed conditions.Risk analysis of crowding variable was statistical significant, with a risk ratio of 2.36 (CI95% 1.01-5.5) with a Pearson x2 of 4.53 p=0.03 . Hygiene was adequate in 73(73.7%) with no statistical significance. Conclusion. The overall seroprevalnce is similar to that reported in other countries for Crowding condition showed to be a relevant factor for PVB19 infection, with a risk of 2.36 higher in the crowed condition group which has not been considered within the elements involved in transmition in previous studies. 2482