Ho-Sheng Wu

Comparison of virus shedding after lived attenuated and pentavalent reassortant rotavirus vaccine

Transmission of rotavirus vaccine or vaccine-reassortant strains to unvaccinated contacts has been reported. Therefore, it is essential to evaluate and characterize the nature of vaccine-virus shedding among rotavirus vaccine recipients. Two groups of healthy infants who received a complete course of RotaTeq (RV5) or Rotarix (RV2) were enrolled (between March 2010 and June 2011) to compare fecal shedding for one month after each vaccine dose. Shedding was assessed using both enzyme immunoassay (EIA) and real-time reverse transcription-polymerase chain reaction (RT-PCR). Eighty-seven infants (34 girls and 53 boys) were enrolled in the study. After the first vaccine dose, the peak time of virus shedding occurred between day 4 and day 7, with positive detection rates of 80-90% by real-time RT-PCR and 20-30% by EIA. In both groups, vaccine shedding occurred as early as one day and as late as 25-28 days. Mixed effects logistic regression analysis of real-time RT-PCR data showed no significant differences between two groups when shedding rates were compared after the first vaccine dose (odds ratio [OR] 1.26; P=0.71) or after the second vaccine dose (odds ratio [OR] 1.26; P=0.99). However, infants receiving RV2 shed significantly higher viral loads than those receiving RV5 when compared after the first vaccine dose (P=0.001) and after the second dose (P=0.039). In terms of shedding rates detected by real-time RT-PCR, vaccine uptake of RV5 or RV2 among infants in Taiwan was comparable. Clinical significance of higher shedding viral loads in RV2 should be further observed.

Screening of dengue virus in field-caught Aedes aegypti and Aedes albopictus (Diptera: Culicidae) by one-step SYBR green-based reverse transcriptase-polymerase chain reaction assay during 2004-2007 in Southern Taiwan.

We carried out virological surveillance of dengue virus (DENV) in field-caught Aedes mosquitoes during 2004-2007 to estimate the monthly prevalence of infected females in dengue high-risk areas of Taiwan. A total of 92,892 Aedes aegypti (43,133 females and 49,759 males) and 79,315 Aedes albopictus (57,319 females and 21,996 males) adults were collected, grouped into 25,654 pools, and processed for virus detection using a one-step SYBR Green-based real-time reverse transcriptase-polymerase chain reaction assay. DENVs were periodically and sympatrically detected in Ae. aegypti females in accordance with major dengue outbreaks and the corresponding dengue serotypes. Only 0.2% of 7628 pools of Ae. aegypti females were positive for DENVs. This resulted in an overall estimated infection rate (maximum likelihood estimation) of 0.970 per 1000 mosquitoes (95% confidence interval [CI]u2009=u20090.53-1.65). The total monthly infection rates ranged from 0.50 to 2.23 per 1000 mosquitoes (95% CIu2009=u20090.03-10.71). When sampling areas were scaled down to the city level, monthly infection rates increased to 0.73-12.59 (95% CIu2009=u20090.06-59.19). Monthly infection rates over all sampling areas and at the city level increased significantly by month. All positive pools were collected in July (one pool), August (two pools), September (one pool), October (three pools), November (four pools), and December (one pool). All four virus serotypes were detected in mosquitoes, which were consistent with dengue serotypes infecting humans in 2004 (DENV-4), 2005 and 2006 (DENV-2 and DENV-3), and 2007 (DENV-1). Our results provide supporting evidence that, in general, DENV infection rates were low in local Aedes mosquito population during 2004-2007 and that transovarial transmission may not be occurring or is occurring at much lower rates than evidenced in some endemic countries.

Diverse origin of P[19] rotaviruses in children with acute diarrhea in Taiwan: Detection of novel lineages of the G3, G5, and G9 VP7 genes†

We previously reported the detection of genotype P[19] rotavirus strains from children hospitalized with acute dehydrating diarrhea during a 5‐year surveillance period in Taiwan. The characterization of five P[19] strains (0.4% of all typed), including three G3P[19], a novel G5P[19], and a unique G9P[19] genotype is described in this study. Phylogenetic analysis of the VP4, VP7, VP6, and NSP4 genes was performed, which demonstrated novel lineages for respective genotypes of the VP4 and the VP7 genes. The sequence similarities of the P[19] VP4 gene among Taiwanese human strains was higher (nt, 91.5–96.2%; aa, 93.7–97.6%) than to other P[19] strains (nt, 83.5–86.6%; aa, 89.4–94.1%) from different regions of the world. The VP7 gene of the three G3P[19] Taiwanese strains shared up to 93.4% nt and 97.5% aa identity to each other but had lower similarity to reference strain sequences available in GenBank (nt, <90.1%; aa, <95.6%). Similarly, the VP7 gene of the novel G5P[19] strain was only moderately related to the VP7 gene of reference G5 strains (nt, 82.2–87.3%; aa, 87.0–93.1%), while the VP7 gene of the single G9P[19] strain was genetically distinct from other known human and animal G9 rotavirus strains (nt, ≤92.0%; aa, ≤95.7%). Together, these findings suggest that the Taiwanese P[19] strains originated by independent interspecies transmission events. Synchronized surveillance of human and animal rotaviruses in Taiwan should identify possible hosts of these uncommon human rotavirus strains. J. Med. Virol. 83:1279–1287, 2011.

Epidemiology and Clinical Peculiarities of Norovirus and Rotavirus Infection in Hospitalized Young Children with Acute Diarrhea in Taiwan, 2009

BACKGROUND/PURPOSEnAcute diarrhea is one of the most common morbidities in pediatrics worldwide. We conducted a study to investigate the incidence of norovirus in young children hospitalized with acute diarrhea in Taiwan and its clinical peculiarity compared with rotavirus gastroenteritis.nnnMETHODSnBetween January and December, 2009, patients younger than 5 years and admitted to hospital with acute diarrhea were randomly selected; and their stool samples were collected and tested for presence of rotavirus and norovirus by enzyme immunoassay and reverse transcription-polymerase chain reaction, respectively. The clinical manifestations and laboratory findings of the enrolled patients were analyzed.nnnRESULTSnA total of 989 cases were enrolled with a mean age of 21.6 ± 13.7 months and a male proportion of 56.0%. Rotavirus and norovirus was detected in 20.2% and 14.6% of all patients, respectively. Genogroup II was the predominant strain of norovirus (80.6%). Children aged 6-36 months accounted for the majority of patients positive for rotavirus and norovirus (73.0% and 81.3%, respectively). The incidences of norovirus and rotavirus infection were higher during winter and early spring. Most patients with rotavirus and norovirus diarrhea experienced vomiting (74.9%vs. 74.8%, respectively) and fever (94.7%vs. 71.3%, respectively).nnnCONCLUSIONnMost young diarrheal patients presenting with vomiting were likely to have norovirus or rotavirus infection. Patients with norovirus diarrhea experienced an absence of, or low-grade fever and longer duration of vomiting compared with those positive for rotavirus infection. A family history of current gastroenteritis may suggest the possibility of norovirus infection.

Identification of porcine rotavirus-like genotype P[6] strains in Taiwanese children.

The molecular characterization of genotype P[6] rotavirus strains collected from children admitted to hospital with acute dehydrating diarrhoea during a 6-year surveillance period in Taiwan is described in this study. In total, three G4P[6] strains, one G5P[6] and one G12P[6] were characterized by sequencing and phylogenetic analysis of the VP4, VP7, VP6 and NSP4 genes. Whilst all four genes of the single Taiwanese G12P[6] strain clustered with the respective genes of globally common human rotavirus strains, the G4 and G5 strains showed remarkable similarities to porcine rotavirus strains and putative porcine-origin human P[19] strains reported previously from Taiwan. The overall proportion of porcine rotavirus-like strains in Taiwan remains around 1u200a% among hospitalized children; however, the circulation and sporadic transmission of these heterotypic strains from pigs to humans could pose a public-health concern. Therefore, continuation of strain monitoring is needed in the vaccine era to detect any possible vaccine breakthrough events associated with the introduction of such heterologous rotavirus strains.

Astrovirus gastroenteritis in hospitalized children of less than 5 years of age in Taiwan, 2009

BACKGROUND/PURPOSEnAcute gastroenteritis is a common illness in children under 5 years old. Although rotavirus is a leading cause, other viruses including astrovirus are also important, but have been the subject of limited studies. This is a prospective study to investigate astrovirus gastroenteritis in hospitalized children in Taiwan.nnnMATERIAL/METHODnFrom January 2009 to December 2009, children below 5 years of age admitted to three hospitals in Taiwan due to acute gastroenteritis were eligible for this study. Stool specimens were sent for the detection of astrovirus by reverse transcriptase polymerase chain reaction; once positive for astrovirus, the sequencing and phylogenetic analysis of each strain was performed.nnnRESULTSnA total of 989 children were enrolled during the study period. The overall positive rate of astrovirus was 1.6%, ranging from 1.03% to 2.26% in different hospitals, while rotavirus accounted for 20.2% of the patients. Six of the 16 children (37.5%) with astroviral infection had documented coinfection with rotavirus. The median age of infection was 28.2 months. The seasonal distribution of astrovirus peaked from April to June. Diarrhea alone (40% vs. 2.1%, p < 0.0001) was significantly more commonly seen than the triad of fever, vomiting and diarrhea (30% vs. 71%, p = 0.0062) in children with astroviral infection alone than in those with rotaviral infection alone. The mean duration of diarrhea was significantly longer in patients with mixed infection than those with astroviral infection alone (6.8 vs. 4.2 days, p = 0.013). Respiratory symptoms were noted in 10 children (62.5%). Serotype HAstV-1 was the most common (68.8%).nnnCONCLUSIONnAstrovirus accounted for 1.6% of infections in children under 5 years hospitalized with acute gastroenteritis in Taiwan. Compared with those caused by rotavirus, the incidence of gastroenteritis in hospitalized children caused by astrovirus was low and the disease severity was mild.

Molecular epidemiology of human G2P[4] rotaviruses in Taiwan, 2004-2011.

In 2006, two rotavirus vaccines (Rotarix and RotaTeq) became available on the private market in Taiwan. Although vaccine coverage is currently low, molecular surveillance of rotavirus strains can provide pertinent information for evaluation of the potential impact of vaccine introduction and infection control. During January 2008-December 2011, children aged <5 years hospitalized with acute gastroenteritis were enrolled from sentinel surveillance hospitals in three geographic areas of Taiwan. Fecal specimens collected from enrolled patients were tested for rotavirus by enzyme immunoassay and reverse transcriptase-polymerase chain reaction. For genotyping, gene specific primer sets were used to amplify and sequence the genes encoding the neutralization antigens, VP7 and VP4. The resulting sequences were then subjected to phylogenetic analysis. In brief, a total of 4,052 fecal specimens were tested and 742 (18%) samples were positive for rotavirus. The annual range of rotavirus positive specimens varied between 16% and 20.7%. Of all specimens, genotype G1P[8] (63.3%) was the predominant strain, followed by G2P[4] (12.5%), G3P[8] (11.7%), and G9P[8] (5.1%). Uncommon strains were also detected in low percentages. We observed that the rotavirus positivity rate steadily decreased from 21% to 16% during 2008-2010, then slightly increased to 20% in 2011, when an increase in the number of G2P[4] cases was observed. Sequence and phylogenetic analysis was carried out to help understand any potential changes of G2P[4] rotaviruses over time. A number of G2P[4] strains collected between 2004 and 2011 were analyzed in detail and our analyses showed marked genetic and antigenic variability in the VP7 and VP4 genes. The Taiwanese strains could be classified into two major G2 VP7 lineages (IV and V) and two major P[4] VP4 lineages (IV and V) and several minor sublineages within lineage IV. Lineage V within both G2 and P[4] represented newly recognized genetic variants of the respective genotypes. The distribution of individual combinations of the G2 and P[4] (sub)lineages showed some temporal variations. This study provides further evidence for the great genetic diversity among G2P[4] strains and helps understand the epidemiological trends of these strains among children in Taiwan.

Cost-effectiveness of rotavirus vaccination programs in Taiwan☆

BACKGROUNDnIn Taiwan, two rotavirus vaccines are available on the private market, but are not included in the National Immunization Program (NIP). To help assess whether to include rotavirus vaccines in the NIP, we examined the potential impact and cost-effectiveness of vaccination, from the health care system perspective alone.nnnMETHODSnWe used a Microsoft Excel-based model to assess rotavirus vaccination impact on rotavirus disease burden and the cost-effectiveness of 2-dose and 3-dose vaccination programs among a birth cohort of Taiwanese children followed for 5 years. Principal model inputs included data on rotavirus disease burden and related healthcare costs, vaccination cost and coverage rates, and vaccine efficacy. Principal model outputs included the number of health-related events and costs averted and incremental cost per disability-adjusted life year averted.nnnRESULTSnA national rotavirus vaccination program, regardless of number of doses per course, would prevent 4 deaths, >10,500 hospitalizations, and >64,000 outpatient visits due to rotavirus infection among children <5 years annually, resulting in ~80%, 90%, and 70% declines in these outcomes, respectively, and a ~

Severe gastroenteritis associated with G3P[9] rotavirus in Taiwan

7 million decline in annual medical costs. A national 2- or 3-dose vaccination program would be cost-saving up to

Putative canine origin of rotavirus strain detected in a child with diarrhea, Taiwan.

13.30/dose (