Abel Paredes

Risk of respiratory syncytial virus infection for infants from low-income families in relationship to age, sex, ethnic group, and maternal antibody level

The risk for hospitalization with respiratory syncytial virus infection during the first year of life was about five per 1,000 live births per year for infants born to low-income families in Houston from 1975 to 1979. The risk varied depending upon the intensity of the epidemic for a given season, the month of birth of the infant, and the level of passively acquired maternal antibody at the time of birth. Over 80% of the children hospitalized were less than 6 months of age; thus, most were born during the six months preceding the peak of RS virus activity. The neutralizing antibody titers in cord sera of 68 infants with culture-proven infections before 6 months of age were significantly lower than those of 575 randomly selected cord samples of infants born during the same period. The level of antibody at the time of birth was directly correlated with age at the time of infection. In addition, infants with more severe illnesses had lower levels of antibody in serum collected near onset of illness than did infants with milder illnesses. These observations demonstrate protection against RS infection in early infancy that is correlated with the level of maternal antibody, but it is not known if this protection is mediated directly by the passively acquired antibody or by some other mechanism.

Influenza in children. Relationship to other respiratory agents.

During the 1975-1976 respiratory disease season, influenza A/Victoria virus exceeded respiratory syncytial (RS) virus as a cause of lower respiratory tract disease (LRD) in children admitted to the hospital. This was a reversal of their usual roles in the etiology of LRD; however, the importance of influenza viruses in causing serious disease in children has been underestimated because of failure to appreciate the full spectrum of disease associated with influenza virus infections. In addition to those with LRD, several children were hospitalized with nonspecific febrile illnesses or CNS involvement. Furthermore, in the ambulatory care setting, influenza viruses were the most important cause of illness that necessitated childrens being brought for medical care during a three-year period. During the peak of epidemics, influenza viruses appeared to interfere with the spread of other major respiratory viruses--particularly RS virus.

Failure of penicillin to eradicate the carrier state of group B streptococcus in infants

Serial cultures were obtained from 12 patients being treated with a form of penicillin for group B streptococcal disease or asymptomatic colonization. These cultures were collected prior to initiation of therapy, during therapy, and at the end of the treatment period. Pencillin eradicated GBS from the involved system (blood, CSF, bone, and joint). Cultures remained positive from at least one of three carrier sites (throat, umbilicus, and rectum) in 70% of patients cultured between days one and eight of treatment and 66% between days 10 and 21. These data demonstrate the failure of penicillin to eradicate GBS from mucous surfaces of young infants.

Evaluation of a Neuraminidase Detection Assay for the Rapid Detection of Influenza A and B Virus in Children

ABSTRACT A prototype version of a new diagnostic assay for influenza A and B (Zstat Flu™) based on detection of viral neuraminidase was evaluated and compared to culture in 196 clinical samples. Children with respiratory illnesses were prospectively evaluated at a pediatricians office and at a large childrens hospital using the neuraminidase assay and viral culture performed on respiratory secretions. Influenza virus was isolated from 51 samples and 83 were positive by the neuraminidase assay. When compared to culture the sensitivity of the assay was 96%, specificity was 77%, positive predictive value was 59%, and negative predictive value was 98%. Testing in the laboratory of pure cultures of bacteria and non-influenza viruses frequently found in the respiratory tract showed 0% cross-reactivity with the neuraminidase assay and 100% specificity for influenza virus in vitro. This new assay provided useful information for the preliminary diagnosis of influenza A and B infections and appears to be suitable for both point-of-care use in the physicians office and rapid diagnosis in a virology laboratory. The high sensitivity makes it particularly useful as a screening test for exclusion of influenza A and B infections. To confirm the diagnosis and exclude a false-positive result, as well as to determine the influenza virus type, a viral culture may be considered.

770 PATHOGENESIS OF RESPIRATORY SYNCYTIAL (RS) VIRUS BRONCHIOLITIS IN INFANTS

RS virus produces yearly epidemics of life-threatening bronchiolitis in infants under 6 months of age. Other workers have theorized that immunopathologic processes involving maternal antibody or sensitization may enhance the severity of these infections. Prospective studies of infants in Houston have not supported these theories; in fact, a postive correllation (p<.05) has been found between the level of maternal antibody and the age of infants at the time of infection suggesting a relative protection of infants by high levels of maternal antibody. Furthermore, the mean maternal antibody titer of 37 infants with infection was significantly lower than that of over 200 random cord sera.Of 70 infants followed from birth, only 14 (20%) were infected with RS virus during the first 6 months of life, but 4 had lower respiratory infections and 2 were hospitalized. The infection rate increased sharply after 6 months of age and almost all were infected by age 2 years. Reinfections, which were mild or inapparent, accounted for 15 of 70 total RS virus infections.Our studies do not support any of the hypotheses of immunopathology for RS virus disease; in fact, the previously impugned maternal factors appear to be relatively protective. Enhancement of these maternal factors that may be transferred to infants may prove to be the safest method for protecting infants during the first months of life.

Evaluation of a Novel Neuraminidase Detection Assay for the Simultaneous Rapid Detection of Influenza A and B Virus in Children

Evaluation of a Novel Neuraminidase Detection Assay for the Simultaneous Rapid Detection of Influenza A and B Virus in Children