Association of different enteroviruses with atopy and allergic diseases in early childhood.

BACKGROUND: Enterovirus (EV) infections, being among the most prevalent viruses worldwide, have been associated with reduced risk of allergic diseases. We sought to determine the association between EVs and allergic sensitization and disease in early childhood. METHODS: The study was carried out in a nested case-control setting within a prospective birth cohort in Finland. We included 138 case children who had specific IgE (s-IgE) sensitization at the age of 5 years and 138 control children without s-IgE sensitization. Allergic disease was recorded at study visits and identified with the ISAAC questionnaire. We screened for the presence of serotype-specific antibodies against 41 EVs at 1-5 years of age and assessed their association with allergic sensitization and disease. RESULTS: The overall number of EV infections did not differ between s-IgE-sensitized children and non-sensitized control children. However, there was a tendency of case children with an allergic disease having less EV infections than their controls. This observation was statistically significant for species A EVs in case children with atopic dermatitis vs. control children: OR 0.6 (95% CI 0.36-0.99), p = .048. CONCLUSION: This study supports the evidence that EV exposure and development of allergic disease are inversely associated. Interestingly, the inverse association was not observed for bare atopic IgE sensitization, but for IgE sensitization coupled with clinical atopic disease. This suggests that environmental factors influencing IgE sensitization may differ from those influencing progression to clinical allergic disease.

Rhinoviruses in infancy and risk of immunoglobulin E sensitization.

Previous data about the role of viruses in the development of allergic immunoglobulin E (IgE) sensitization are contradictory. The aim of this study was to determine the possible associations between exposure to different viruses (rhinovirus, enterovirus, norovirus, and parechovirus) during the first year of life and IgE sensitization. Viruses were analyzed from stool samples collected monthly from infants participating in a prospective birth cohort study. From that study, 244 IgE sensitized case children and 244 nonsensitized control children were identified based on their allergen-specific IgE antibody levels at the age of 6, 18, and 36 months. Stool samples (n = 4576) from the case and control children were screened for the presence of rhinovirus, enterovirus, norovirus, and parechovirus RNA by reverse transcription quantitative polymerase chain reaction. The study showed that rhinovirus was the most prevalent virus detected, present in 921 (20%) samples. None of the viruses were associated with IgE sensitization in the full cohort but after stratifying by sex, the number of rhinovirus positive samples was inversely associated with IgE sensitization in boys (odds ratio [OR]: 0.81; 95% confidence interval [CI]: 0.69-0.94; P = 0.006). There was also a temporal relation between rhinoviruses and IgE sensitization, as rhinovirus exposure during the first 6 months of life was associated with a reduced risk of subsequent IgE sensitization in boys (OR: 0.76; 95% CI: 0.6-0.94; P = 0.016). In conclusion, early exposure to rhinoviruses was inversely associated with IgE sensitization but this protective association was restricted to boys.

The relationship between breastfeeding and reported respiratory and gastrointestinal infection rates in young children.

BACKGROUND: Although breastfeeding is touted as providing many health benefits to infants, some aspects of this relationship remain poorly understood. METHODS: The Environmental Determinants of Diabetes in the Young (TEDDY) is a prospective longitudinal study that follows children from birth through childhood, and collects data on illness events, breastfeeding duration, and time to introduction of formula or foods at 3 month intervals up until 4 years of age and at 6 months intervals thereafter. Exclusive and non-exclusive breastfeeding is examined in relation to the 3-month odds of a respiratory or gastrointestinal infection for 6861 children between the ages of 3-18 months, and 5666 children up to the age of 4 years. Analysis was performed using logistic regression models with generalized estimating equation methodology. All models were adjusted for potential confounding variables. RESULTS: At 3-6 months of age, breastfeeding was found to be inversely associated with the odds of respiratory infections with fever (OR = 0.82, 95% CI = 0.70-0.95), otitis media (OR = 0.76, 95% CI = 0.62-0.94), and infective gastroenteritis (OR = 0.55, 95% CI = 0.46-0.70), although the inverse association with respiratory illnesses was observed only for girls during the winter months. Between 6 and 18 months of age, breastfeeding within any 3 month period continued to be inversely associated with the odds of ear infection and infective gastroenteritis, and additionally with the odds of conjunctivitis, and laryngitis and tracheitis, over the same 3 month period within this age range. However, breastfeeding in this group was associated with increased reports of common cold. Duration of exclusive breastfeeding was inversely associated with the odds of otitis media up to 48 months of age (OR = 0.97, 95% CI = 0.95-0.99) after breastfeeding had stopped. CONCLUSIONS: This study demonstrates that breastfeeding can be protective against multiple respiratory and gastrointestinal acute illnesses in some children up to at least 6 months of age, with duration of exclusive breastfeeding being somewhat protective of otitis media even after breastfeeding has stopped. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT00279318 . Date of registration: January 17, 2006 (proactively registered). First Posted: January 19, 2006.

Correction to: Respiratory infections are temporally associated with initiation of type 1 diabetes autoimmunity: the TEDDY study.

The authors regret that the SNP in SH2B3 was incorrectly referred to as rs3184505 instead of rs3184504 on both mentions in this paper (Methods section and Table 1).

Pandemrix® vaccination is not associated with increased risk of islet autoimmunity or type 1 diabetes in the TEDDY study children.

AIMS/HYPOTHESIS: During the A/H1N1 2009 (A/California/04/2009) pandemic, mass vaccination with a squalene-containing vaccine, Pandemrix®, was performed in Sweden and Finland. The vaccination was found to cause narcolepsy in children and young adults with the HLA-DQ 6.2 haplotype. The aim of this study was to investigate if exposure to Pandemrix® similarly increased the risk of islet autoimmunity or type 1 diabetes. METHODS: In The Environmental Determinants of Diabetes in the Young (TEDDY) study, children are followed prospectively for the development of islet autoimmunity and type 1 diabetes. In October 2009, when the mass vaccination began, 3401 children at risk for islet autoimmunity and type 1 diabetes were followed in Sweden and Finland. Vaccinations were recorded and autoantibodies against insulin, GAD65 and insulinoma-associated protein 2 were ascertained quarterly before the age of 4 years and semi-annually thereafter. RESULTS: By 5 August 2010, 2413 of the 3401 (71%) children observed as at risk for an islet autoantibody or type 1 diabetes on 1 October 2009 had been vaccinated with Pandemrix®. By 31 July 2016, 232 children had at least one islet autoantibody before 10 years of age, 148 had multiple islet autoantibodies and 96 had developed type 1 diabetes. The risk of islet autoimmunity was not increased among vaccinated children. The HR (95% CI) for the appearance of at least one islet autoantibody was 0.75 (0.55, 1.03), at least two autoantibodies was 0.85 (0.57, 1.26) and type 1 diabetes was 0.67 (0.42, 1.07). In Finland, but not in Sweden, vaccinated children had a lower risk of islet autoimmunity (0.47 [0.29, 0.75]), multiple autoantibodies (0.50 [0.28, 0.90]) and type 1 diabetes (0.38 [0.20, 0.72]) compared with those who did not receive Pandemrix®. The analyses were adjusted for confounding factors. CONCLUSIONS/INTERPRETATION: Children with an increased genetic risk for type 1 diabetes who received the Pandemrix® vaccine during the A/H1N1 2009 pandemic had no increased risk of islet autoimmunity, multiple islet autoantibodies or type 1 diabetes. In Finland, the vaccine was associated with a reduced risk of islet autoimmunity and type 1 diabetes.

Enterovirus infection during pregnancy is inversely associated with atopic disease in the offspring.

BACKGROUND: Prenatal environment has been shown to influence child's risk of atopic diseases. Laboratory-confirmed data about the role of maternal infections during pregnancy is scarce. OBJECTIVE: The aim of this study was to determine the associations between serologically confirmed maternal infections during pregnancy and atopic disease in the offspring. METHODS: This was a nested case-control study within a prospective birth cohort study. Altogether 202 atopic case children and 333 matched non-atopic control children were included. Atopic outcome was defined as having an atopic disease and IgE sensitization by the age of 5 years. We analysed serologically acute enterovirus (EV), influenza virus A (IAV) and Mycoplasma pneumoniae (M. pneumoniae) infections during pregnancy, and mother's seropositivity against human cytomegalovirus (CMV) and Helicobacter pylori. RESULTS: Maternal EV infection during pregnancy was inversely associated with atopic outcome in the offspring (odds ratio 0.43; 95% confidence interval: 0.23-0.80, P = 0.008). Acute IAV or M. pneumoniae infections or seropositivity against CMV or Helicobacter pylori were not associated with the atopic outcome. CONCLUSIONS AND CLINICAL RELEVANCE: Our results suggest that maternal EV infections during pregnancy are inversely associated with atopic disease in the offspring. Our finding provides further support to the previous studies suggesting an important role of the in utero environment in the development of atopic diseases.

Respiratory infections are temporally associated with initiation of type 1 diabetes autoimmunity: the TEDDY study.

AIMS/HYPOTHESIS: Respiratory infections and onset of islet autoimmunity are reported to correlate positively in two small prospective studies. The Environmental Determinants of Diabetes in the Young (TEDDY) study is the largest prospective international cohort study on the environmental determinants of type 1 diabetes that regularly monitors both clinical infections and islet autoantibodies. The aim was to confirm the influence of reported respiratory infections and to further characterise the temporal relationship with autoantibody seroconversion. METHODS: During the years 2004-2009, 8676 newborn babies with HLA genotypes conferring an increased risk of type 1 diabetes were enrolled at 3 months of age to participate in a 15 year follow-up. In the present study, the association between parent-reported respiratory infections and islet autoantibodies at 3 month intervals up to 4 years of age was evaluated in 7869 children. Time-dependent proportional hazard models were used to assess how the timing of respiratory infections related to persistent confirmed islet autoimmunity, defined as autoantibody positivity against insulin, GAD and/or insulinoma antigen-2, concordant at two reference laboratories on two or more consecutive visits. RESULTS: In total, 87,327 parent-reported respiratory infectious episodes were recorded while the children were under study surveillance for islet autoimmunity, and 454 children seroconverted. The number of respiratory infections occurring in a 9 month period was associated with the subsequent risk of autoimmunity (p < 0.001). For each 1/year rate increase in infections, the hazard of islet autoimmunity increased by 5.6% (95% CI 2.5%, 8.8%). The risk association was linked primarily to infections occurring in the winter (HR 1.42 [95% CI 1.16, 1.74]; p < 0.001). The types of respiratory infection independently associated with autoimmunity were common cold, influenza-like illness, sinusitis, and laryngitis/tracheitis, with HRs (95% CI) of 1.38 (1.11, 1.71), 2.37 (1.35, 4.15), 2.63 (1.22, 5.67) and 1.76 (1.04, 2.98), respectively. CONCLUSIONS/INTERPRETATION: Recent respiratory infections in young children correlate with an increased risk of islet autoimmunity in the TEDDY study. Further studies to identify the potential causative viruses with pathogen-specific assays should focus especially on the 9 month time window leading to autoantibody seroconversion.

Factors That Increase Risk of Celiac Disease Autoimmunity After a Gastrointestinal Infection in Early Life.

BACKGROUND & AIMS: Little is known about the pathogenic mechanisms of gluten immunogenicity in patients with celiac disease. We studied temporal associations between infections and the development of celiac disease autoimmunity, and examined effects of HLA alleles, rotavirus vaccination status, and infant feeding. METHODS: We monitored 6327 children in the United States and Europe carrying HLA risk genotypes for celiac disease from 1 to 4 years of age for presence of tissue transglutaminase autoantibodies (the definition of celiac disease autoimmunity), until March 31, 2015. Parental reports of gastrointestinal and respiratory infections were collected every third month from birth. We analyzed time-varying relationships among reported infections, rotavirus vaccination status, time to first introduction of gluten, breastfeeding, and risk of celiac disease autoimmunity using proportional hazard models. RESULTS: We identified 13,881 gastrointestinal infectious episodes (GIE) and 79,816 respiratory infectious episodes. During the follow-up period, 732 of 6327 (11.6%) children developed celiac disease autoimmunity. A GIE increased the risk of celiac disease autoimmunity within the following 3 months by 33% (hazard ratio [HR], 1.33; 95% confidence interval [CI], 1.11-1.59). This risk increased 2-fold among children born in winter and introduced to gluten before age 6 months (HR, 2.08; 95% CI, 1.46-2.98), and increased 10-fold among children without HLA-DQ2 alleles and breastfed for fewer than 4 months (HR, 9.76; 95% CI, 3.87-24.8). Risk of celiac disease autoimmunity was reduced in children vaccinated against rotavirus and introduced to gluten before age 6 months (HR, 0.57; 95% CI, 0.36-0.88). CONCLUSIONS: Gastrointestinal infections increase the risk of celiac disease autoimmunity in children with genetic susceptibility to this autoimmune disorder. The risk is modified by HLA genotype, infant gluten consumption, breastfeeding, and rotavirus vaccination, indicating complex interactions among infections, genetic factors, and diet in the etiology of celiac disease in early childhood.

A method for reporting and classifying acute infectious diseases in a prospective study of young children: TEDDY.

BACKGROUND: Early childhood environmental exposures, possibly infections, may be responsible for triggering islet autoimmunity and progression to type 1 diabetes (T1D). The Environmental Determinants of Diabetes in the Young (TEDDY) follows children with increased HLA-related genetic risk for future T1D. TEDDY asks parents to prospectively record the child's infections using a diary book. The present paper shows how these large amounts of partially structured data were reduced into quantitative data-sets and further categorized into system-specific infectious disease episodes. The numbers and frequencies of acute infections and infectious episodes are shown. METHODS: Study subjects (n = 3463) included children who had attended study visits every three months from age 3 months to 4 years, without missing two or more consecutive visits during the follow-up. Parents recorded illnesses prospectively in a TEDDY Book at home. The data were entered into the study database during study visits using ICD-10 codes by a research nurse. TEDDY investigators grouped ICD-10 codes and fever reports into infectious disease entities and further arranged them into four main categories of infectious episodes: respiratory, gastrointestinal, other, and unknown febrile episodes. Incidence rate of infections was modeled as function of gender, HLA-DQ genetic risk group and study center using the Poisson regression. RESULTS: A total of 113,884 ICD-10 code reports for infectious diseases recorded in the database were reduced to 71,578 infectious episodes, including 74.0% respiratory, 13.1% gastrointestinal, 5.7% other infectious episodes and 7.2% febrile episodes. Respiratory and gastrointestinal infectious episodes were more frequent during winter. Infectious episode rates peaked at 6 months and began declining after 18 months of age. The overall infectious episode rate was 5.2 episodes per person-year and varied significantly by country of residence, sex and HLA genotype. CONCLUSIONS: The data reduction and categorization process developed by TEDDY enables analysis of single infectious agents as well as larger arrays of infectious agents or clinical disease entities. The preliminary descriptive analyses of the incidence of infections among TEDDY participants younger than 4 years fits well with general knowledge of infectious disease epidemiology. This protocol can be used as a template in forthcoming time-dependent TEDDY analyses and in other epidemiological studies.

Gastrointestinal Infections Modulate the Risk for Insulin Autoantibodies as the First-Appearing Autoantibody in the TEDDY Study.

OBJECTIVE: To investigate gastrointestinal infection episodes (GIEs) in relation to the appearance of islet autoantibodies in The Environmental Determinants of Diabetes in the Young (TEDDY) cohort. RESEARCH DESIGN AND METHODS: GIEs on risk of autoantibodies against either insulin (IAA) or GAD (GADA) as the first-appearing autoantibody were assessed in a 10-year follow-up of 7,867 children. Stool virome was characterized in a nested case-control study. RESULTS: GIE reports (odds ratio [OR] 2.17 [95% CI 1.39-3.39]) as well as Norwalk viruses found in stool (OR 5.69 [1.36-23.7]) at <1 year of age were associated with an increased IAA risk at 2-4 years of age. GIEs reported at age 1 to <2 years correlated with a lower risk of IAA up to 10 years of age (OR 0.48 [0.35-0.68]). GIE reports at any other age were associated with an increase in IAA risk (OR 2.04 for IAA when GIE was observed 12-23 months prior [1.41-2.96]). Impacts on GADA risk were limited to GIEs <6 months prior to autoantibody development in children <4 years of age (OR 2.16 [1.54-3.02]). CONCLUSIONS: Bidirectional associations were observed. GIEs were associated with increased IAA risk when reported before 1 year of age or 12-23 months prior to IAA. Norwalk virus was identified as one possible candidate factor. GIEs reported during the 2nd year of life were associated with a decreased IAA risk.

Land Cover of Early-Life Environment Modulates the Risk of Type 1 Diabetes.

OBJECTIVE: Environmental microbial exposures have been implicated to protect against immune-mediated diseases such as type 1 diabetes. Our objective was to study the association of land cover around the early-life dwelling with the development of islet autoimmunity and type 1 diabetes to evaluate the role of environmental microbial biodiversity in the pathogenesis. RESEARCH DESIGN AND METHODS: Association between land cover types and the future risk of type 1 diabetes was studied by analyzing land cover types classified according to Coordination of Information on the Environment (CORINE) 2012 and 2000 data around the dwelling during the first year of life for 10,681 children genotyped for disease-associated HLA-DQ alleles and monitored from birth in the Type 1 Diabetes Prediction and Prevention (DIPP) study. Land cover was compared between children who developed type 1 diabetes (n = 271) or multiple diabetes-associated islet autoantibodies (n = 384) and children without diabetes who are negative for diabetes autoantibodies. RESULTS: Agricultural land cover around the home was inversely associated with diabetes risk (odds ratio 0.37, 95% CI 0.16-0.87, P = 0.02 within a distance of 1,500 m). The association was observed among children with the high-risk HLA genotype and among those living in the southernmost study region. Snow cover on the ground seemed to block the transfer of the microbial community indoors, leading to reduced bacterial richness and diversity indoors, which might explain the regional difference in the association. In survival models, an agricultural environment was associated with a decreased risk of multiple islet autoantibodies (hazard ratio [HR] 1.60, P = 0.008) and a decreased risk of progression from single to multiple autoantibody positivity (HR 2.07, P = 0.001) compared with an urban environment known to have lower environmental microbial diversity. CONCLUSIONS: The study suggests that exposure to an agricultural environment (comprising nonirrigated arable land, fruit trees and berry plantations, pastures, natural pastures, land principally occupied by agriculture with significant areas of natural vegetation, and agroforestry areas) early in life is inversely associated with the risk of type 1 diabetes. This association may be mediated by early exposure to environmental microbial diversity.

The association between stressful life events and respiratory infections during the first 4 years of life: The Environmental Determinants of Diabetes in the Young study.

The aim of this study was to conduct a prospective analysis of the association between negative life events (NLEs) and respiratory infections in children genetically at risk for islet autoimmunity (IA) and type 1 diabetes (T1D). Long- and short-term temporal associations between NLEs and rate of respiratory infection episodes (RIEs) in 5,618 children in The Environmental Determinants of Diabetes in the Young study for at least 1 up to 4 years were analysed. All models were adjusted for demographic, day care, season of infection, and psychosocial factors associated with the rate of child RIEs between study visits. The rate of child RIEs was 26% higher in Europe (Sweden, Finland, Germany) than in the United States (rate ratio [RR] = 1.26, p < 0.001). However, the percentage of child NLEs (odds ratio [OR] = 1.18, p < 0.001) and mother NLEs (OR = 1.83, p < 0.001) was higher in the United States compared with Europe. In both continents (Europe, RR = 1.12, p < 0.001; United States, RR = 1.07, p = 0.006), high child cumulative NLEs (>1 NLE per year since study inception) was significantly associated with an increased rate of child RIEs. This large-scale prospective study confirms observations that stress may increase the susceptibility for infections in paediatric populations and suggests at least one mechanism by which stress could increase risk for IA and T1D in genetically at risk children.

Real-time PCR for rapid diagnosis of entero- and rhinovirus infections using LightCycler.

BACKGROUND: PCR techniques have proved to be more sensitive than traditional cell culture in the diagnosis of enterovirus and rhinovirus infections and are widely used in clinical virus laboratories. However, PCR assays are relatively time-consuming and labor intensive, particularly if separate hybridization steps are used to confirm the specificity of positive findings. OBJECTIVES: The aim of the present study was to develop fast and sensitive real-time PCR assay, which would allow simultaneous detection of entero- and rhinoviruses and their quantification in clinical and experimental samples. STUDY DESIGN: Two real-time RT-PCR protocols were developed using LightCycler (LC) technology; SYBRGreen and hybridization probe assays. The sensitivity of these assays to detect entero- and rhinoviruses was compared with that of a traditional reference RT-PCR-hybridization assay and cell culture. All PCR protocols used the same primers amplifying the 5'-non coding region (NCR) of entero- and rhinoviruses. The LC probe assay and the reference RT-PCR used almost identical detection probes, which bind to enterovirus specific amplicons. RESULTS AND CONCLUSIONS: Both real-time PCR assays were equally sensitive as the reference RT-PCR-assay and all were more sensitive than cell culture. Both real-time assays quantified reliably the amount of the virus and took much shorter time than the reference RT-PCR. As the real-time SYBRGreen assay detects both entero- and rhinoviruses it can be used for primary screening of samples, which can be positive for either of these viruses. The real-time probe-assay can confirm the presence of enterovirus in SYBRGreen positive samples or it can be used for selective screening of enteroviruses e.g. from CSF samples.

Temporal relationship between human parechovirus 1 infection and otitis media in young children.

BACKGROUND: Human parechovirus (HPeV) 1 is a common virus that infects almost everyone during childhood. Because clinical symptoms are poorly documented, we evaluated the symptoms associated with HPeV1 infection in a cohort of children followed prospectively from birth at 3-month intervals. METHODS: Symptoms such as fever, cough, those of the common cold, otitis media, and gastroenteritis were determined from hospital records and from questionnaires administered to the parents of 59 children during regular study visits. HPeV1 infections were diagnosed by measuring neutralizing antibodies in follow-up serum samples. Additionally, HPeV RNA was analyzed in middle ear fluid (MEF) and nasopharyngeal aspirate samples from 33 patients with otitis media by reverse-transcription polymerase chain reaction. RESULTS: Otitis media showed a clear association with HPeV1 infection-it developed in 50% of the 3-month follow-up periods that yielded evidence for HPeV1 infection but in only 14% of the HPeV1-negative periods (odds ratio [OR], 6.14 [95% confidence interval {CI}, 2.75-13.77]). In children with recurring otitis media, MEF samples were positive for HPeV in 15% of episodes. Cough was also associated with HPeV1 infection, but this association was weaker (OR, 3.67 [95% CI, 1.66-8.09]). Other symptoms were not linked to HPeV1 infection. CONCLUSIONS: HPeV1 infections are common in childhood and may cause otitis media and cough.

Human parechovirus 1 infections in young children--no association with type 1 diabetes.

The epidemiology, transmission and clinical symptoms of human parechoviruses [HPeV, classified earlier as enteroviruses; echovirus 22 (HPeV1) and echovirus 23 (HPeV2)] remain poorly characterized. Enteroviruses and one parechovirus species, the Ljungan virus, have been associated with type 1 diabetes in humans and rodents. The occurrence of human parechovirus 1 (HPeV1) infections in young children and their possible association with type 1 diabetes was evaluated. The prospective birth cohort study comprised 221 Finnish children carrying genetic type 1 diabetes susceptibility and who were observed from birth. Thirty-four children developed multiple diabetes-associated autoantibodies, and 18 children progressed to clinical type 1 diabetes during the follow-up. HPeV1 infections were diagnosed by measuring neutralizing antibodies from the follow-up sera taken every 3-12 months. In addition, viral RNA was analysed by RT-PCR from stool samples taken every month from six of the participants. HPeV1 infections were found to occur early in childhood. The median age of infection was 18 months and 20% of the children had had an infection by the age of 1 year. The number of infections started to increase from the age of 6 months and most children had their first infection by 36 months. Nearly all (99%) mothers were HPeV1 antibody positive. No difference was found in infection frequency between boys and girls, nor between prediabetic, diabetic and control subjects. Most infections (87%) occurred during autumn, winter and spring.

Enterovirus infections are associated with the induction of beta-cell autoimmunity in a prospective birth cohort study.

Enterovirus infections have been associated with the manifestation of clinical type 1 diabetes in a number of reports, and recent prospective studies have suggested that enterovirus infections may initiate the autoimmune process, leading to the disease. In the present study, we analyzed the role of enterovirus infections in a Finnish birth cohort study, Diabetes Prediction and Prevention (DIPP), in which all newborn infants are screened for diabetes-associated HLA-DQB1 alleles, and those with an increased genetic risk are invited for prospective follow-up. Enterovirus infections were diagnosed by serology and reverse transcriptase-polymerase chain reaction (RT-PCR) from serum samples taken from birth every 3-6 months. Case children included 41 infants who became positive for diabetes-associated autoantibodies during the observation. Control children comprised altogether 196 infants who remained autoantibody negative and were matched for the time of birth, sex, and HLA-DQB1 alleles. Enterovirus infections were more frequent in case children than in control children (P = 0.004), and the average enterovirus antibody levels were also higher in the case children (P = 0.003). Enterovirus infections were particularly frequent during the 6-month period preceding the first detection of autoantibodies: 51% of the case children compared with 28% of the control children had an infection in that time interval (P = 0.003). There was no difference in the frequency of adenovirus infections between the groups (P = 0.9). The present results imply that enterovirus infections are associated with the appearance of beta-cell autoantibodies. A possible causal relationship is supported by the clustering of infections to the time when autoantibodies appeared.