Influenza epidemiology among hospitalized children in Stockholm, Sweden 1998-2014.

Background: Influenza remains a common reason for the hospitalization of children. There is a need for long term studies that are also population based. We describe the epidemiology of severe influenza in a defined population 1998-2014.

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.

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.

Performance of the Simplexa™ Flu A/B & RSV Direct Kit on respiratory samples collected in saline solution.

Background: Molecular assays for diagnosis of influenza A, influenza B, and respiratory syncytial virus (RSV) with short turnaround time are of considerable clinical importance. We have evaluated the diagnostic performance of the Simplexa(™) Flu A/B & RSV Direct Kit, which has a run time of 60 min, using different types of respiratory samples collected from patients with a suspected respiratory tract infection, including materials not previously evaluated on this kit.

Methods: In total, 210 clinical respiratory samples were analyzed using both the Simplexa direct assay and a laboratory-developed assay (LDA).

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.

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.

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.

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.

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.

Molecular epidemiology and genetic variability of respiratory syncytial virus (RSV) in Stockholm, 2002-2003.

The epidemiology and genetic variability of circulating respiratory syncytial virus (RSV) strains in Stockholm during the season 2002-2003 were studied in consecutive RSV isolates derived from respiratory samples and diagnosed in the laboratory. Two hundred thirty-four viruses were sequenced. The samples were mainly from children under 1 year old (79%).

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.

A novel varicella-zoster virus gE mutation discovered in two Swedish isolates.

Background: Two VZV glycoprotein E (gE D150N) mutant strains were collected in North America in 1995 and in 1999. We now report a novel VZV gE mutant virus discovered in Europe in two VZV strains collected in Stockholm, Sweden, in 1990 and 1999.

Objectives: To characterize the two isolates identified among a total of 634 VZV isolates collected over a 15-year period at the Karolinska University Hospital.

Evaluation of the ReSSQ assay in relation to the COBAS AMPLICOR CMV MONITOR test and an in-house nested PCR method for detection of cytomegalovirus DNA.

The ReSSQ CMV assay is a novel commercially available kit for quantification of cytomegalovirus (CMV), based on real-time PCR with a peptide nucleic acid probe coupled with a single dye. In combination with the LightCycler, the ReSSQ CMV assay was evaluated with respect to specificity, PCR inhibition, linearity, reproducibility, and sensitivity. All nontested CMV materials were negative, and the assay was not inhibited by the use of different anticoagulants or other factors that may influence blood samples.

Identification of viral agents associated with diarrhea in young children during a winter season in Beijing, China.

Background: Viral diarrhea remains a major cause of childhood morbidity and mortality worldwide. Although rotavirus was extensively studied in China, few comprehensive studies of all viral agents related to diarrhea in children have been conducted.

Objectives: Our study was performed to investigate the role of enteric viruses in acute diarrhea in our country and to evaluate methods that could be used in routine diagnostics.

Molecular epidemiology of norovirus infections in Stockholm, Sweden, during the years 2000 to 2003: association of the GGIIb genetic cluster with infection in children.

The incidence of norovirus-associated gastroenteritis and the molecular epidemiology of norovirus strains were studied during three seasons (2000-2001, 2001-2002, and 2002-2003) among patients of all ages, mainly from the Stockholm region in Sweden. A total of 3,252 fecal samples were analyzed by reverse transcription-PCR. The incidences of norovirus infection among adults were 23, 26, and 30% during the three seasons studied and 18, 11, and 15% among children 0 to 15 years of age.

Respiratory virus infections in Stockholm during seven seasons: a retrospective study of laboratory diagnosis.

A retrospective analysis of the virological findings in all respiratory samples (7303) analysed at the laboratory of Karolinska Hospital between 1993 and 2000 was performed. The findings were studied according to age and seasonal variation, and the methods were evaluated. Most samples were from children.

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.