Clinical and epidemiologic characteristics of human bocavirus in Danish infants: results from a prospective birth cohort study.

BACKGROUND: Human bocavirus (HBoV) is a recently discovered parvovirus that has been detected in respiratory samples from children with acute respiratory tract infection (ARTI) and in feces from children with gastroenteritis. However, its role as a causative agent of respiratory disease is not determined. METHODS: We investigated the presence of HBoV by real-time polymerase-chain reaction of nasal swab specimens obtained from 228 healthy children followed in the community from birth to 1 year of age for a 2-year period from 2004 to 2006. Nasal swabs and symptom diaries were collected at monthly home visits. RESULTS: HBoV was detected in 57 (8.2%) of 697 nasal swab specimens from children with ARTI, in 1 (2.3%) of 44 swabs from children with diarrhea, and in 13 (8.6%) of 152 swabs from asymptomatic children. HBoV was present mainly during the winter months. An additional respiratory virus was identified in 27 (47.4%) HBoV-positive samples. Thirty-four (68%) of 50 children with ARTI shed HBoV for less than 1 month, 13 (26%) for 2 months, 2 (4%) for 3 months, and 1 (2%) for 4 months. Seven asymptomatic children shed HBoV for less than 1 month, 2 children for 2 months, and 1 asymptomatic child had 5 HBoV-positive nasal swabs detected for 6 consecutive months. HBoV infection was associated with maternal smoking, being born in the winter, and predisposition to asthma. CONCLUSIONS: Asymptomatic carriage of HBoV is common in infants <1 year of age, and an HBoV-positive test result does not imply that HBoV is the cause of the illness.

A community study of clinical traits and risk factors for human metapneumovirus and respiratory syncytial virus infection during the first year of life.

Human metapneumovirus (hMPV) and respiratory syncytial virus (RSV) are important respiratory pathogens with similar symptomatology. The aim of this prospective birth cohort study was to identify risk factors for an hMPV or RSV infection during the first year of life in unselected healthy children. We followed 217 children from birth to 1 year of age. Nasal swabs and symptom diaries were collected monthly. Anti-hMPV and anti-RSV IgG antibodies by age 1 year were detected by ELISA, and nasal swabs were analysed for hMPV and RSV by RT-PCR. Logistic regression was used for risk factor analysis. Anti-hMPV IgG was found in 38 children (17.5%), and anti-RSV IgG in 172 children (79%). Risk factors for being anti-hMPV IgG-positive were: (1) being born in the spring (OR = 2.36; 95% CI:1.06-5.27), and (2) having older siblings (OR = 3.82; 95% CI:1.75-8.34). Risk factors for being anti-RSV IgG-positive were: (1) gestational age <38 weeks (OR = 3.39; 95% CI:1.42-8.05), (2) increasing paternal age (OR = 1.85 per 5 yrs; 95% CI:1.28-2.68), and (3) wall-to-wall carpeting (OR = 3.15; 95% CI:1.29-7.68). Being born in the spring was associated with decreased odds of being anti-RSV IgG-positive (OR = 0.27, 95% CI:0.09-0.85). Risk factors for RSV hospitalisation (n = 11) were: (1) older siblings (OR = 4.49; 95% CI: 1.08-18.73) and (2) smoking in the household (OR = 5.06; 95% CI: 1.36-18.76). Exclusive breastfeeding for the first 14 days of life protected against hospitalisation (OR = 0.21; 95% CI:0.06-0.79). In conclusion, this study identifies risk factors for mild and asymptomatic hMPV infections in infancy.