Respiratory viruses associated with community-acquired pneumonia in children: matched case-control study.

BACKGROUND: Community-acquired pneumonia (CAP) is the leading cause of death in children worldwide and a substantial proportion of childhood CAP is caused by viruses. A better understanding of the role of virus infections in this condition is needed to improve clinical management and preventive measures. The aim of the study was therefore to assess the association between specific respiratory viruses and childhood CAP. METHODS: A case-control study was conducted during 3 years in Stockholm, Sweden. Cases were children aged ≤5 years with radiological CAP. Healthy controls were consecutively enrolled at child health units during routine visits and matched to cases on age and calendar time. Nasopharyngeal aspirates were obtained and analysed by real-time PCR for 15 viruses. Multivariate conditional logistic regression was used to account for coinfections with other viruses and baseline characteristics. RESULTS: A total of 121 cases, of which 93 cases met the WHO criteria for radiological pneumonia, and 240 controls were included in the study. Viruses were detected in 81% of the cases (n=98) and 56% of the controls (n=134). Influenza virus, metapneumovirus and respiratory syncytial virus were detected in 60% of cases and were significantly associated with CAP with ORs >10. There was no association with parainfluenza virus, human enterovirus or rhinovirus and coronavirus and bocavirus were negatively associated with CAP. CONCLUSIONS: Our study indicates viral CAP is an underestimated disease and points out hMPV as a new important target for the prevention of childhood CAP.

Children with multiple viral respiratory infections are older than those with single viruses.

AIM: To study the clinical impact of multiple viral respiratory infections compared to single infections. METHODS: Demographic data from 37 multiple infection periods in children <5 years of age were compared to data from 193 episodes with single infections. Clinical data derived from patient records of the multiple infection episodes were further compared to data from 93 matched control episodes with single infections. RESULTS: The mean age of patients with multiple viral findings was 12.7 months, compared to 5.7 months for those with single findings (p < 0.01). Wheezing was the most common diagnosis in both groups, except among children who were only infected with the coronavirus. No differences were found regarding duration of hospitalisation, oxygen treatment or admittance to the intensive care unit. CONCLUSION: Children with multiple viral findings in their respiratory secretions were older than those with a single detected virus. Otherwise, no major differences in comorbidity, presentation or clinical outcome were observed between the two groups.

Development and implementation of a molecular diagnostic platform for daily rapid detection of 15 respiratory viruses.

Acute respiratory tract infections are caused by a large number of viruses. Diagnostic methods have until recently been available only for a limited number of these viruses. With the objective to achieve sensitive assays for all respiratory viruses, a rational workflow in the laboratory, and a short turn-around time, a real-time PCR diagnostic platform for daily rapid detection of 15 respiratory viruses was developed. The system was evaluated on 585 stored nasopharyngeal aspirates from hospitalized children. Previous analysis by immunofluorescence and virus isolation identified viruses in 37% of the samples while the new PCR diagnostic panel detected 57% virus positive samples. The new platform was introduced in the laboratory in October 2007 and has then fully replaced the standard immunofluorescence assay for rapid detection of viruses and virus isolation.

Norovirus strains belonging to the GII.4 genotype dominate as a cause of nosocomial outbreaks of viral gastroenteritis in Sweden 1997--2005. Arrival of new variants is associated with large nation-wide epidemics.

BACKGROUND: In recent years an increase of the incidence of nosocomial outbreaks caused by noroviruses has been observed throughout Sweden, with high peaks noted in the winter seasons 2002/2003 and 2004/2005, respectively. OBJECTIVES: To phylogenetically characterize norovirus strains causing nosocomial outbreaks from 1997 to 2005 and estimate the impact of norovirus-like disease on the Swedish health care system during the peak season 2002/2003 when a new variant of norovirus occurred. STUDY DESIGN: Stool samples from 115 randomly selected nosocomial outbreaks occurring during 1997--2005 throughout Sweden were studied by RT-PCR and sequencing. In addition, to investigate the impact on the health-care system, a questionnaire was distributed to infection control units (n=90) serving all Swedish hospitals, nursing homes and other health-care institutions during the largest epidemic of nosocomial outbreaks. RESULTS: Sequencing of 279 nucleotides of the norovirus RNA polymerase gene in stools containing norovirus RNA showed that strains belonging to the GII.4 genotype dominated. Each of the two large epidemics was due to a new variant within this cluster. The questionnaire revealed that 30,000-35,000 episodes of nosocomial norovirus-like infections occurred in 80 of 82 major Swedish hospitals affected in 2002/2003. CONCLUSION: New norovirus variants within the cluster GGII.4 may have a major impact on the health-care system.

Cytomegalovirus infection and neonatal outcome in extremely preterm infants after freezing of maternal milk.

BACKGROUND: Cytomegalovirus (CMV) infection acquired from breast milk can cause serious illness in extremely preterm (EPT) infants (<28 weeks). Some neonatal centers freeze maternal milk (MM) to prevent CMV transmission; however, this practice is controversial. In this study, we assessed the CMV transmission rate and neonatal outcome in EPT infants after routine freezing of all MM. METHODS: EPT infants (n = 140) and their mothers were randomized to the intervention group (only freeze-thawed MM) or the control group (combined fresh and freeze-thawed MM). Freeze-thawed MM was frozen at -20°C for ≥3 days before thawing. Mothers had serological tests for CMV, and MM was analyzed for CMV by polymerase chain reaction and CMV culture. Infants underwent CMV screening with urine analysis by CMV-polymerase chain reaction and CMV culture until 12 weeks of age. RESULTS: Congenital CMV infection was detected in 2% of screened infants. The CMV transmission rate in infants fed with CMV-DNA positive milk was 8% (3 of 37) in the intervention group and 6% (2 of 33) in controls. All infants infected by CMV were asymptomatic. The final per-protocol analysis included 56 infants in the intervention group and 65 controls. Neonatal mortality was comparable between the groups (7% vs. 6%). Neonatal morbidity was similar, except for late onset Candida sepsis, which was more frequent in the controls (12% vs. 0%). CONCLUSIONS: Routine freezing of all MM did not affect the rate of CMV transmission but may help to prevent fungal sepsis in EPT infants. This observation merits further investigation.

Detection of herpes simplex virus type 1, herpes simplex virus type 2 and varicella-zoster virus in skin lesions. Comparison of real-time PCR, nested PCR and virus isolation.

BACKGROUND: Herpes simplex virus type 1 (HSV-1), herpes simplex virus type 2 (HSV-2) and varicella-zoster virus (VZV) cause a wide range of signs and symptoms, varying from trivial mucocutaneous lesions to life-threatening infections, especially in immuno-suppressed patients. Since antiviral drugs are available, rapid and sensitive laboratory diagnosis of these virus infections is important. OBJECTIVE: To set up and evaluate HSV-1, HSV-2 and VZV qualitative real-time PCR on the Lightcycler system and to compare the results with those of the 'in-house' nested PCR and virus isolation. STUDY DESIGN: 110 consecutive samples from dermal or genital lesions from patients suspected of having HSV infections and another 110 samples from patients with suspected VZV infections were tested with real-time PCR, nested PCR and virus isolation. RESULTS: 24 samples (22%) were positive for HSV-1 by virus isolation and nested PCR, whereas 26 (24%) were positive by real-time PCR. HSV-2 was detected in 28 samples (25%) by virus isolation, in 41 (37%) by nested PCR and in 40 (36%) by real-time PCR. VZV was isolated in 15 samples (14%) and VZV DNA was detected in 51 samples (46%) by nested PCR as well as by real-time PCR. Nucleic acid amplification increased the detection rate of HSV-2 and VZV DNA in particular compared to virus isolation. No significant difference in sensitivity was found between real-time PCR and nested PCR. CONCLUSION: Real-time PCR has the advantage of rapid amplification, a reduced risk for contamination and it is a suitable method for diagnosis of VZV and HSV in specimens from skin lesions.

Clinical utility of PCR for common viruses in acute respiratory illness.

BACKGROUND: Acute respiratory illness (ARI) accounts for a large proportion of all visits to pediatric health facilities. Quantitative real-time polymerase chain reaction (qPCR) analyses allow sensitive detection of viral nucleic acids, but it is not clear to what extent specific viruses contribute to disease because many viruses have been detected in asymptomatic children. Better understanding of how to interpret viral findings is important to reduce unnecessary use of antibiotics. OBJECTIVE: To compare viral qPCR findings from children with ARI versus asymptomatic control subjects. METHODS: Nasopharyngeal aspirates were collected from children aged ≤5 years with ARI and from individually matched, asymptomatic, population-based control subjects during a noninfluenza season. Samples were analyzed by using qPCR for 16 viruses. RESULTS: Respiratory viruses were detected in 72.3% of the case patients (n = 151) and 35.4% of the control subjects (n = 74) (P = .001). Rhinovirus was the most common finding in both case patients and control subjects (47.9% and 21.5%, respectively), with a population-attributable proportion of 0.39 (95% confidence interval: 0.01 to 0.62). Metapneumovirus, parainfluenza viruses, and respiratory syncytial virus were highly overrepresented in case patients. Bocavirus was associated with ARI even after adjustment for coinfections with other viruses and was associated with severe disease. Enterovirus and coronavirus were equally common in case patients and control subjects. CONCLUSIONS: qPCR detection of respiratory syncytial virus, metapneumovirus, or parainfluenza viruses in children with ARI is likely to be causative of disease; detection of several other respiratory viruses must be interpreted with caution due to high detection rates in asymptomatic children.

Complications attributable to rotavirus-induced diarrhoea in a Swedish paediatric population: report from an 11-year surveillance.

The aim of this retrospective observational study was to evaluate age, length of hospital stay and development of complications in children hospitalized with community- or nosocomially- acquired rotavirus gastroenteritis (RV GE). In total, medical records of 984 children with RV GE were analysed retrospectively. The median age was 13.8 months (3 weeks to 99 months) in children with community acquired RV GE (n=723) and 9.0 months (range 3 weeks to 82 months) in children with nosocomially acquired RV GE (n=261). During this 11-y surveillance, only 2 children were admitted twice for a RV GE, suggesting development of subsequent protective immunity against severe rotavirus gastroenteritis after the first episode. Complications occurred in 16.5% of the children with community acquired RV GE and only in 1.9% of the nosocomially acquired RV GE. Identified complications in children with community acquired RV GE were: severe dehydration resulting in intensive care (1.7%), death (0.1%), hypertonic dehydration (9.1%), seizures (4.0%) and encephalitis with abnormal EEG (1.7%). The median age of children in need of intensive care was 9.1 months and in those developing hypertonic dehydration 10.8 months, both significantly lower than in children with no complications (p<0.05). Interestingly, the age of children developing seizures and signs of encephalitis was significantly higher than in children with no complications (p<0.01).

Transmission of cytomegalovirus to extremely preterm infants through breast milk.

AIM: To evaluate the rate and clinical expression of postnatal cytomegalovirus (CMV) infection transmitted through breast milk in extremely preterm infants. METHODS: Ten extremely preterm infants and their six mothers were included. Maternal CMV serology was determined. Breast milk samples and urine samples from the infants were screened for CMV. Symptoms and laboratory findings of CMV infected infants were documented. All infants received partly fresh and/or defrosted breast milk. RESULTS: CMV-DNA was found in breast milk in four of five CMV-seropositive mothers. Two infants were infected by CMV. They were the only infants fed with breast milk positive for viral culture. One infant developed hepatic affection concurrent with viral excretion in urine. This infant was later diagnosed with cystic fibrosis. CONCLUSION: This study supports that CMV transmission through breast milk can aggravate the clinical course in extremely preterm infants with preexisting hepatic conditions.