ECHO 9 VIRUS INFECTION AND CONGENITAL ABNORMALITIES: A NEGATIVE REPORT

Approximately 200,000 residents of Hennepin and Ramsey counties in Minnesota developed an aseptic meningitis syndrome during the summer and fall of 1957. One fourth of the patients had a maculopapular rash very similar to that of rubella. The etiologic agent was found to be ECHO virus type 9. This epidemic provided an opportunity to determine whether infection with this virus during the first trimester of pregnancy could be related to the appearance of congenital defects such as occurs in rubella. From March 3 through June 13, 1958, 10,109 liveborn infants and 105 stillborn infants were delivered in the 12 Minneapolis and 10 St. Paul hospitals serving these two counties. All mothers had been exposed to the 1957 epidemic. Public health nurses interviewed 9,990 mothers in the hospitals within a few days after birth for detailed histories of infection during pregnancy. On the basis of these interviews it was judged that 6.5% of the mothers had historic evidence of an ECHO 9 infection during pregnancy. Serologic evidence of ECHO 9 infection in the recent past was present in 19% of 853 antibody titrations carried out on cord blood specimens from abnormals and normals (controls). To discover anomalies not recognized at birth, a follow-up was carried out 11 to 12 months later by the public health nurses by telephone interviews of some 9,600 mothers. There were 356 major and minor congenital anomalies recognized during the first year of life. An additional 63 hernias were diagnosed during the first year for a total of 419 anomalies found in 10,109 live births in the study. This rate of 41.4 total anomalies per 1,000 live births, or 4.1%, is well within the rates reported by other authors. A total of 39.6% of the anomalies were diagnosed at birth and 60.4% during the first year of life. Of the anomalies, 61% occurred in males and 39% in females; 1.5% of the infants had major abnormalities and 0.74% died as a result of these anomalies during their first year of life. There were 105 stillbirths recorded, or 10.4 per 1,000 live births. This compares with a rate of 13.6 for Hennepin and Ramsey counties for the year. Among the stillbirths, 11.4% died from congenital anomalies, in comparison with 10.95% statewide for the year. A statistical analysis of the findings which compares the ECHO 9 antibody titer distributions in the cord blood of the normal and the abnormal infants does not justify the conclusion that ECHO 9 infection in the mother increases the incidence of congenital anomalies in the offspring. The only exception to this generalization is in the case of skin abnormalities, where there is a statistical suggestion of association.