Congenital cytomegalovirus infection in San Luis Potosi, Mexico

The incidence of congenital cytomegalovirus infection in Mexico is unknown. We evaluated the presence of cytomegalovirus infection in 560 newborn infants at a public general hospital. There were five (0.89%) infected newborns. Infants with congenital infection were more likely to be born to primigravid mothers (P = 0.01) and were more often from rural areas (P = 0.058) than were noninfected newborns. Cytomegalovirus (CMV) is the most common cause of congenital infection. 1 Long term neurologic or audiologic sequelae occur in infants born with either symptomatic or asymptomatic infection. 2, 3 The incidence of congenital CMV infection is reported from 0.4 to 2.3% of live births in different populations, although higher incidences (up to 14% in a study from The Gambia) have been reported. 1, 4 To date there are no published reports describing the incidence of this infection in Mexico. Objectives. To determine the incidence of congenital CMV infection at a public general hospital (Hospital Central “Dr. Ignacio Morones Prieto”) in San Luis Potosí, Mexico. To identify demographic factors that are associated with the presence of infection in this population. Materials and methods. Patients. All newborns admitted to the well baby nursery from September 23, 2001 to December 11, 2001, at the Hospital Central “Dr. Ignacio Morones Prieto,” San Luis Potosí, Mexico, were eligible for this study. Samples were collected Monday through Saturday. The study was approved by the institutional ethics committee, and written informed consent was obtained from the mother or guardian of each infant. Samples. A saliva specimen was collected using a cotton-tipped swab from participating newborns. 5 The swab was placed in viral transport medium and kept on wet ice until its arrival to the Microbiology Laboratory at the Universidad Autónoma de San Luis Potosí. Specimens were processed within 1 h from collection and inoculated onto human foreskin fibroblast monolayers. Cultures were observed under light microscopy for 21 days, and the presence of characteristic cytopathic effect was used to detect the presence of CMV. 6 Demographic information. Maternal demographic information as well as newborn information was recorded in a standardized form. Statistical analysis. Categoric variables were compared with Fisher’s exact test, and continuous variables were analyzed with a two sided t test or Mann-Whitney test as appropriate. Results. During the 3-month study period 815 newborns were admitted to the well baby nursery; 599 (73.5%) were enrolled in the study. Bacterial or fungal contamination was observed in 39 (6.5%) specimens and were not evaluable for the presence of CMV. Thus 560 (68.7% of all admissions to the nursery during the study period) infants were included in the final analysis. Cytomegalovirus was recovered from five [0.89%; 95% confidence interval (95% CI) 0.26 to 1.95] newborns included in the analysis. Demographic and newborn information of infected and noninfected newborns is presented in Table 1. None of the infected infants showed symptoms of congenital cytomegalovirus disease. All infants with congenital infection were born to primigravid mothers (incidence of 2.24% in this group; 95% CI 0.55 to 5). The incidence of congenital infection in mothers who were from rural areas was 2% (95% CI 0.55 to 5). The number of positive cultures did not allow for multivariate analysis to be performed.TABLE 1: Maternal demographics and newborn characteristics of cytomegalovirus infected and noninfected infantsDiscussion. Despite the high frequency of congenital CMV infection reported throughout the world, there is no information regarding the incidence of this infection in Mexico. The aim of this study was to determine the incidence of this infection at our hospital. The population that we studied was predominantly of low income, without private or public insurance. CMV seroprevalence in our maternal population has not been studied, but a study in Cuernavaca, Mexico, among low income child-bearing age women showed presence of anti-CMV antibodies in 91.6% of subjects. 7 The incidence of congenital infection we found (0.89%) was within the range of 0.4 to 2.3% reported in different studies throughout the world. 8–11 Babies born to primigravid mothers had a higher incidence of congenital infection than those born to nonprimigravid mothers. Other studies have found similar results. 12 Younger mothers have been shown consistently to be at higher risk of delivering a congenitally infected infant. 13, 14 Some authors have suggested that the association of low parity and congenital infection may be confounded by young maternal age, with maternal age being one of the most important factors that identify populations at risk for congenital CMV infection. 14 Although not statistically significant in our study, infected babies were also born to younger women compared with the rest of the study group. Sample size did not allow for multivariate analysis to be performed and to assess the independent contribution for congenital infection of these risk factors. It is also of interest that infants born to women from rural areas were more likely to be infected than those born to women from urban areas (P = 0.058). Several studies have shown that women from disadvantaged socioeconomic classes are more likely to deliver a congenitally infected infant. 13, 15 None of the newborns with congenital infection presented any signs of CMV disease at birth. However, they are at risk for development of hearing deficits during childhood. The incidence of sensorineural hearing loss in children with asymptomatic CMV infection was 7.5 to 15%. 3, 16 Follow-up was available for only one of the infected babies (the one who was not from a rural area) despite repeated attempts to locate all of them. At 6 months of age his developmental examination was normal; a head computed tomography scan and hearing test were also normal. In summary the incidence of congenital CMV infection in our population was 0.89%. This is the first report describing the incidence of this infection in Mexico. Our continued efforts to determine the presence of congenital CMV infection will focus on primigravid women, especially those from rural areas who appear to be at highest risk to deliver a congenitally infected newborn. Acknowledgments. We thank Dr. Gail J. Demmler for her advice. This work was supported by Grant CO1-FAI-10-9.68 from Fondo de Apoyo a la Investigación, Universidad Autónoma de San Luis Potosí.