Publications by authors named "Ka Ian Tam"

14 Publications

  • Page 1 of 1

Characterisation of a rare, reassortant human G10P[14] rotavirus strain detected in Honduras.

Mem Inst Oswaldo Cruz 2018 Jan;113(1):9-16

Centers for Disease Control and Prevention, Gastroenteritis and Respiratory Viruses Laboratory Branch, Atlanta, Georgia, USA.

Background: Although first detected in animals, the rare rotavirus strain G10P[14] has been sporadically detected in humans in Slovenia, Thailand, United Kingdom and Australia among other countries. Earlier studies suggest that the strains found in humans resulted from interspecies transmission and reassortment between human and bovine rotavirus strains.

Objectives: In this study, a G10P[14] rotavirus genotype detected in a human stool sample in Honduras during the 2010-2011 rotavirus season, from an unvaccinated 30-month old boy who reported at the hospital with severe diarrhea and vomiting, was characterised to determine the possible evolutionary origin of the rare strain.

Methods: For the sample detected as G10P[14], 10% suspension was prepared and used for RNA extraction and sequence independent amplification. The amplicons were sequenced by next-generation sequencing using the Illumina MiSeq 150 paired end method. The sequence reads were analysed using CLC Genomics Workbench 6.0 and phylogenetic trees were constructed using PhyML version 3.0.

Findings: The next generation sequencing and phylogenetic analyses of the 11-segmented genome of the G10P[14] strain allowed classification as G10-P[14]-I2-R2-C2-M2-A3-N2-T6-E2-H3. Six of the genes (VP1, VP2, VP3, VP6, NSP2 and NSP4) were DS-1-like. NSP1 and NSP5 were AU-1-like and NSP3 was T6, which suggests that multiple reassortment events occurred in the evolution of the strain. The phylogenetic analyses and genetic distance calculations showed that the VP7, VP4, VP6, VP1, VP3, NSP1, NSP3 and NSP4 genes clustered predominantly with bovine strains. NSP2 and VP2 genes were most closely related to simian and human strains, respectively, and NSP5 was most closely related to a rhesus strain.

Main Conclusions: The genetic characterisation of the G10P[14] strain from Honduras suggests that its genome resulted from multiple reassortment events which were possibly mediated through interspecies transmissions.
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http://dx.doi.org/10.1590/0074-02760170083DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5719537PMC
January 2018

Effectiveness of Monovalent and Pentavalent Rotavirus Vaccines in Guatemala.

Clin Infect Dis 2016 May;62 Suppl 2:S121-6

Center for Health Studies, Universidad del Valle de Guatemala.

Background: Concerns remain about lower effectiveness and waning immunity of rotavirus vaccines in resource-poor populations. We assessed vaccine effectiveness against rotavirus in Guatemala, where both the monovalent (RV1; 2-dose series) and pentavalent (RV5; 3-dose series) vaccines were introduced in 2010.

Methods: A case-control evaluation was conducted in 4 hospitals from January 2012 to August 2013. Vaccine status was compared between case patients (children with laboratory-confirmed rotavirus diarrhea) and 2 sets of controls: nondiarrhea "hospital" controls (matched by birth date and site) and nonrotavirus "test-negative" diarrhea controls (adjusted for age, birth month/year, and site). Vaccine effectiveness ([1 - odds ratio of vaccination] × 100%) was computed using logistic regression models.

Results: We evaluated 213 case patients, 657 hospital controls, and 334 test-negative controls. Effectiveness of 2-3 doses of a rotavirus vaccine against rotavirus requiring emergency department visit or hospitalization was 74% (95% confidence interval [CI], 58%-84%) with hospital controls, and 52% (95% CI, 26%-69%) with test-negative controls. Using hospital controls, no significant difference in effectiveness was observed between infants 6-11 months (74% [95% CI, 18%-92%]) and children ≥12 months of age (71% [95% CI, 44%-85%]) (P= .85), nor between complete courses of RV1 (63% [95% CI, 23%-82%]) and RV5 (69% [95% CI, 29%-87%]) (P= .96). An uncommon G12P[8] strain, partially heterotypic to strains in both vaccines, was identified in 89% of cases.

Conclusions: RV1 and RV5 were similarly effective against severe rotavirus diarrhea caused by a heterotypic strain in Guatemala. This supports broader implementation of rotavirus vaccination in low-income countries where >90% global deaths from rotavirus occur.
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http://dx.doi.org/10.1093/cid/civ1208DOI Listing
May 2016

One-step multiplex real-time RT-PCR assay for detecting and genotyping wild-type group A rotavirus strains and vaccine strains (Rotarix® and RotaTeq®) in stool samples.

PeerJ 2016 11;4:e1560. Epub 2016 Jan 11.

Division of Viral Diseases, Gastroenteritis and Respiratory Viruses Laboratory Branch, Centers for Disease Control and Prevention , Atlanta, Georgia , United States of America.

Background. Group A rotavirus (RVA) infection is the major cause of acute gastroenteritis (AGE) in young children worldwide. Introduction of two live-attenuated rotavirus vaccines, RotaTeq® and Rotarix®, has dramatically reduced RVA associated AGE and mortality in developed as well as in many developing countries. High-throughput methods are needed to genotype rotavirus wild-type strains and to identify vaccine strains in stool samples. Quantitative RT-PCR assays (qRT-PCR) offer several advantages including increased sensitivity, higher throughput, and faster turnaround time. Methods. In this study, a one-step multiplex qRT-PCR assay was developed to detect and genotype wild-type strains and vaccine (Rotarix® and RotaTeq®) rotavirus strains along with an internal processing control (Xeno or MS2 RNA). Real-time RT-PCR assays were designed for VP7 (G1, G2, G3, G4, G9, G12) and VP4 (P[4], P[6] and P[8]) genotypes. The multiplex qRT-PCR assay also included previously published NSP3 qRT-PCR for rotavirus detection and Rotarix® NSP2 and RotaTeq® VP6 qRT-PCRs for detection of Rotarix® and RotaTeq® vaccine strains respectively. The multiplex qRT-PCR assay was validated using 853 sequence confirmed stool samples and 24 lab cultured strains of different rotavirus genotypes. By using thermostable rTth polymerase enzyme, dsRNA denaturation, reverse transcription (RT) and amplification (PCR) steps were performed in single tube by uninterrupted thermocycling profile to reduce chances of sample cross contamination and for rapid generation of results. For quantification, standard curves were generated using dsRNA transcripts derived from RVA gene segments. Results. The VP7 qRT-PCRs exhibited 98.8-100% sensitivity, 99.7-100% specificity, 85-95% efficiency and a limit of detection of 4-60 copies per singleplex reaction. The VP7 qRT-PCRs exhibited 81-92% efficiency and limit of detection of 150-600 copies in multiplex reactions. The VP4 qRT-PCRs exhibited 98.8-100% sensitivity, 100% specificity, 86-89% efficiency and a limit of detection of 12-400 copies per singleplex reactions. The VP4 qRT-PCRs exhibited 82-90% efficiency and limit of detection of 120-4000 copies in multiplex reaction. Discussion. The one-step multiplex qRT-PCR assay will facilitate high-throughput rotavirus genotype characterization for monitoring circulating rotavirus wild-type strains causing rotavirus infections, determining the frequency of Rotarix® and RotaTeq® vaccine strains and vaccine-derived reassortants associated with AGE, and help to identify novel rotavirus strains derived by reassortment between vaccine and wild-type strains.
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http://dx.doi.org/10.7717/peerj.1560DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4734446PMC
February 2016

Multiplexed one-step RT-PCR VP7 and VP4 genotyping assays for rotaviruses using updated primers.

J Virol Methods 2015 Oct 29;223:96-104. Epub 2015 Jul 29.

Gastroenteritis and Respiratory Viruses Laboratory Branch, Division of Viral Diseases, NCIRD, Centers for Disease Control and Prevention, Atlanta, GA 30329, USA.

The current two-step VP7 and VP4 genotyping RT-PCR assays for rotaviruses have been linked consistently to genotyping failure in an estimated 30% of RVA positive samples worldwide. We have developed a VP7 and VP4 multiplexed one-step genotyping assays using updated primers generated from contemporary VP7 and VP4 sequences. To determine assay specificity and sensitivity, 17 reference virus strains, 6 non-target gastroenteritis viruses and 725 clinical samples carrying the most common VP7 (G1, G2, G3, G4, G9, and G12) and VP4 (P[4], P[6], P[8], P[9] and P[10]) genotypes were tested in this study. All reference RVA strain targets yielded amplicons of the expected sizes and non-target genotypes and gastroenteritis viruses were not detected by either assay. Out of the 725 clinical samples tested, the VP7 and VP4 assays were able to assigned specific genotypes to 711 (98.1%) and 714 (98.5%), respectively. The remaining unassigned samples were re-tested for RVA antigen using EIA and qRT-PCR assays and all were found to be negative. The overall specificity, sensitivity and limit of detection of the VP7 assay were in the ranges of 99.0-100%, 94.0-100% and 8.6×10(1) to 8.6×10(2) copies of RNA/reaction, respectively. For the VP4 assay, the overall specificity, sensitivity and limit of detection assay were in the ranges of 100%, 94.0-100% and ≤1 to 8.6×10(2) copies of RNA/reaction, respectively. Here we report two highly robust, accurate, efficient, affordable and documentable gel-based genotyping systems which are capable of genotyping 97.8% of the six common VP7 and 98.3% of the five common VP4 genotypes of RVA strains which are responsible for approximately 88.2% of all RVA infections worldwide.
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http://dx.doi.org/10.1016/j.jviromet.2015.07.012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5818709PMC
October 2015

Evaluation of BBL™ Sensi-Discs™ and FTA® cards as sampling devices for detection of rotavirus in stool samples.

J Virol Methods 2015 Sep 30;222:41-6. Epub 2015 May 30.

Gastroenteritis and Respiratory Viruses Laboratory Branch, Division of Viral Diseases, NCIRD, Centers for Disease Control and Prevention, Atlanta, GA 30329 USA. Electronic address:

Rotavirus is the most important cause of severe childhood gastroenteritis worldwide. Rotavirus vaccines are available and rotavirus surveillance is carried out to assess vaccination impact. In surveillance studies, stool samples are stored typically at 4°C or frozen to maintain sample quality. Uninterrupted cold storage is a problem in developing countries because of power interruptions. Cold-chain transportation of samples from collection sites to testing laboratories is costly. In this study, we evaluated the use of BBL™ Sensi-Discs™ and FTA(®) cards for storage and transportation of samples for virus isolation, EIA, and RT-PCR testing. Infectious rotavirus was recovered after 30 days of storage on Sensi-Discs™ at room temperature. We were able to genotype 98-99% of samples stored on Sensi-Discs™ and FTA(®) cards at temperatures ranging from -80°C to 37°C up to 180 days. A field sampling test using samples prepared and shipped from Cameroon, showed that both matrices yielded 100% genotyping success compared with whole stool and Sensi-Discs™ demonstrated 95% concordance with whole stool in EIA testing. The utilization of BBL™ Sensi-Discs™ and FTA(®) cards for stool sample storage and shipment has the potential to have great impact on global public health by facilitating surveillance and epidemiological investigations of rotavirus strains worldwide at a reduced cost.
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http://dx.doi.org/10.1016/j.jviromet.2015.05.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4605405PMC
September 2015

Outbreak of Gastroenteritis in Adults Due to Rotavirus Genotype G12P[8].

Clin Infect Dis 2015 Aug 13;61(4):e20-5. Epub 2015 Apr 13.

Chicago Department of Public Heath, Illinois.

Background: Rotavirus infection in adults is poorly understood and few rotavirus outbreaks among US adults have been reported in the literature. We describe an outbreak due to genotype G12P[8] rotavirus among medical students, faculty, and guests who attended a formal dinner event in April 2013.

Methods: A web-based questionnaire was distributed to event attendees to collect symptom and exposure data. A clinical case was defined as a person who developed diarrhea after attending the formal event. A laboratory-confirmed case was defined as a clinical case who attended the formal event, with rotavirus detected in stool by enzyme immunoassay or reverse transcription-polymerase chain reaction (RT-PCR) assay.

Results: Among 334 dinner attendees, 136 (41%) completed the web-based questionnaire; 58 (43%) respondents reported illness. Symptom onset ranged from 1 to 8 days, with peak onset 3 days after the event. In addition to diarrhea, predominant symptoms included fever (91%), abdominal pain (84%), and vomiting (49%). The median duration of illness was 2.5 days. Thirteen (22%) of 58 cases sought medical attention; none were hospitalized. Analysis of food exposures among questionnaire respondents did not identify significant associations between any specific food or drink item and illness. Stool specimens were negative for bacterial pathogens by culture and negative for norovirus by RT-PCR assay; 4 specimens were positive for rotavirus by enzyme immunoassay or PCR. G12P[8]-R1-C1-M1-A1-N1-T1-E1-H1 was identified as the causative full-genome genotype.

Conclusions: Rotavirus outbreaks can occur among adults, including young adults. Health professionals should consider rotavirus as a cause of acute gastroenteritis in adults.
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http://dx.doi.org/10.1093/cid/civ294DOI Listing
August 2015

Full genomic characterization of a novel genotype combination, G4P[14], of a human rotavirus strain from Barbados.

Infect Genet Evol 2014 Dec 22;28:524-9. Epub 2014 Sep 22.

Gastroenteritis and Respiratory Viruses Laboratory Branch, Division of Viral Diseases, NCIRD, Centers for Disease Control and Prevention, Atlanta, GA, USA. Electronic address:

Since 2004, the Pan American Health Organization (PAHO) has carried out rotavirus surveillance in Latin America and the Caribbean. Here we report the characterization of human rotavirus with the novel G-P combination of G4P[14], detected through PAHO surveillance in Barbados. Full genome sequencing of strain RVA/Human-wt/BRB/CDC1133/2012/G4P[14] revealed that its genotype is G4-P[14]-I1-R1-C1-M1-A8-N1-T1-E1-H1. The possession of a Genogroup 1 (Wa-like) backbone distinguishes this strain from other P[14] rotavirus strains. Phylogenetic analyses suggested that this strain was likely generated by genetic reassortment between human, porcine and possibly other animal rotavirus strains and identified 7 lineages within the P[14] genotype. The results of this study reinforce the potential role of interspecies transmission in generating human rotavirus diversity through reassortment. Continued surveillance is important to determine if rotavirus vaccines will protect against strains that express the P[14] rotavirus genotype.
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http://dx.doi.org/10.1016/j.meegid.2014.09.020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4605422PMC
December 2014

Real-time RT-PCR assays to differentiate wild-type group A rotavirus strains from Rotarix(®) and RotaTeq(®) vaccine strains in stool samples.

Hum Vaccin Immunother 2014 16;10(3):767-77. Epub 2013 Dec 16.

Gastroenteritis and Respiratory Viruses Laboratory Branch; Division of Viral Diseases; National Center for Immunization and Respiratory Diseases; Centers for Disease Control and Prevention; Atlanta, GA USA.

Group A rotaviruses (RVA) are the leading cause of severe diarrhea in young children worldwide. Two live-attenuated RVA vaccines, Rotarix(®) and RotaTeq(®) are recommended by World Health Organization (WHO) for routine immunization of all infants. Rotarix(®) and RotaTeq(®) vaccines have substantially reduced RVA associated mortality but occasionally have been associated with acute gastroenteritis (AGE) cases identified in vaccinees and their contacts. High-throughput assays are needed to monitor the prevalence of vaccine strains in AGE cases and emergence of new vaccine-derived strains following RVA vaccine introduction. In this study, we have developed quantitative real-time RT-PCR (qRT-PCR) assays for detection of Rotarix(®) and RotaTeq(®) vaccine components in stool samples. Real-time RT-PCR assays were designed for vaccine specific targets in the genomes of Rotarix(®) (NSP2, VP4) and RotaTeq(®) (VP6, VP3-WC3, VP3-human) and validated on sequence confirmed stool samples containing vaccine strains, wild-type RVA strains, and RVA-negative stools. For quantification, standard curves were generated using dsRNA transcripts derived from RVA gene segments. Rotarix(®) NSP2 and VP4 qRT-PCR assays exhibited 92-100% sensitivity, 99-100% specificity, 94-105% efficiency, and a limit of detection of 2-3 copies per reaction. RotaTeq(®) VP6, VP3-WC3, and VP3-human qRT-PCR assays displayed 100% sensitivity, 94-100% specificity, 91-102% efficiency and limits of detection of 1 copy, 2 copies, and 140 copies, respectively. These assays permit rapid identification of Rotarix(®) and RotaTeq(®) vaccine components in stool samples from clinical and surveillance studies and will be helpful in determining the frequency of vaccine strain-associated AGE.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4130254PMC
http://dx.doi.org/10.4161/hv.27388DOI Listing
March 2015

Comparison of 2 assays for diagnosing rotavirus and evaluating vaccine effectiveness in children with gastroenteritis.

Emerg Infect Dis 2013 Aug;19(8):1245-52

Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.

We compared rotavirus detection rates in children with acute gastroenteritis (AGE) and in healthy controls using enzyme immunoassays (EIAs) and semiquantitative real-time reverse transcription PCR (qRT-PCR). We calculated rotavirus vaccine effectiveness using different laboratory-based case definitions to determine which best identified the proportion of disease that was vaccine preventable. Of 648 AGE patients, 158 (24%) were EIA positive, and 157 were also qRT-PCR positive. An additional 65 (10%) were qRT-PCR positive but EIA negative. Of 500 healthy controls, 1 was EIA positive and 24 (5%) were qRT-PCR positive. Rotavirus vaccine was highly effective (84% [95% CI 71%-91%]) in EIA-positive children but offered no significant protection (14% [95% CI -105% to 64%]) in EIA-negative children for whom virus was detected by qRT-PCR alone. Children with rotavirus detected by qRT-PCR but not by EIA were not protected by vaccination, suggesting that rotavirus detected by qRT-PCR alone might not be causally associated with AGE in all patients.
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http://dx.doi.org/10.3201/eid1908.130461DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3739503PMC
August 2013

Sensitive and specific quantitative detection of rotavirus A by one-step real-time reverse transcription-PCR assay without antecedent double-stranded-RNA denaturation.

J Clin Microbiol 2013 Sep 12;51(9):3047-54. Epub 2013 Jul 12.

Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.

A real-time quantitative reverse transcription-PCR (qRT-PCR) assay using the recombinant thermostable Thermus thermophilus (rTth) enzyme was developed to detect and quantify rotavirus A (RVA). By using rTth polymerase, significant improvement was achieved over the existing real-time RT-PCR assays, which require denaturation of the RVA double-stranded RNA (dsRNA) prior to assay setup. Using a dsRNA transcript for segment 7, which encodes the assay target NSP3 gene, the limit of detection for the improved assay was calculated to be approximately 1 genome copy per reaction. The NSP3 qRT-PCR assay was validated using a panel of 1,906 stool samples, 23 reference RVA strains, and 14 nontarget enteric virus samples. The assay detected a diverse number of RVA genotypes and did not detect other enteric viruses, demonstrating analytical sensitivity and specificity for RVA in testing stool samples. A XenoRNA internal process control was introduced and detected in a multiplexed qRT-PCR format. Because it does not require an antecedent dsRNA denaturation step, this assay reduces the possibility of sample cross-contamination and requires less hands-on time than other published qRT-PCR protocols for RVA detection.
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http://dx.doi.org/10.1128/JCM.01192-13DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3754639PMC
September 2013

Effectiveness of monovalent rotavirus vaccine in Bolivia: case-control study.

BMJ 2013 Jun 19;346:f3726. Epub 2013 Jun 19.

Viral Gastroenteritis Team, DVD, NCIRD, MS-A34, Centers for Disease Control and Prevention, 1600 Clifton Road, NE, Atlanta, GA 30333, USA.

Objective: To evaluate the effectiveness of two doses of a monovalent rotavirus vaccine (RV1) against hospital admission for rotavirus in Bolivia.

Design: Case-control study.

Setting: Six hospitals in Bolivia, between March 2010 and June 2011.

Participants: 400 hospital admissions for rotavirus, 1200 non-diarrhea hospital controls, and 718 rotavirus negative hospital controls.

Main Outcome Measures: Odds of antecedent vaccination between case patients and controls; effectiveness of vaccination ((1-adjusted odds ratio)×100), adjusted for age and other confounders; and stratified effectiveness by dose, disease severity, age group, and serotype.

Results: In comparison with non-diarrhea controls, case patients were more likely to be male and attend day care but less likely to have chronic underlying illness, higher level maternal education, and telephones and computers in their home. Rotavirus negative controls were somewhat more similar to case patients but also were more likely to be male and attend day care and less likely to have higher level maternal education and computers in their homes. The adjusted effectiveness of RV1 against hospital admission for rotavirus was 69% (95% confidence interval 54% to 79%) with rotavirus negative controls and 77% (65% to 84%) with non-diarrhea controls. The effectiveness of one dose of RV1 was 36% and 56%, respectively. With both control groups, protection was sustained through two years of life, with similar efficacy against hospital admission among children under 1 year (64% and 77%) and over 1 year of age (72% and 76%). RV1 provided significant protection against diverse serotypes, partially and fully heterotypic to the G1P[8] vaccine. Effectiveness using the two control groups was 80% and 85% against G9P[8], 74% and 93%% against G3P[8], 59% and 69% against G2P[4], and 80% and 87% against G9P[6] strains.

Conclusion: The monovalent rotavirus vaccine conferred high protection against hospital admission for diarrhea due to rotavirus in Bolivian children. Protection was sustained through two years of life against diverse serotypes different from the vaccine strain.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3687514PMC
http://dx.doi.org/10.1136/bmj.f3726DOI Listing
June 2013

Two rotavirus outbreaks caused by genotype G2P[4] at large retirement communities: cohort studies.

Ann Intern Med 2012 Nov;157(9):621-31

Centers for Disease Control and Prevention, Atlanta, GA 30333, USA.

Background: Outbreaks of rotavirus gastroenteritis in elderly adults are reported infrequently but are often caused by G2P[4] strains. In 2011, outbreaks were reported in 2 Illinois retirement facilities.

Objective: To implement control measures, determine the extent and severity of illness, and assess risk factors for disease among residents and employees.

Design: Cohort studies using surveys and medical chart abstraction.

Setting: Two large retirement facilities in Cook County, Illinois.

Patients: Residents and employees at both facilities and community residents with rotavirus disease.

Measurements: Attack rates, hospitalization rates, and rotavirus genotype.

Results: At facility A, 84 of 324 residents (26%) were identified with clinical or laboratory-confirmed rotavirus gastroenteritis (median age, 84 years) and 11 (13%) were hospitalized. The outbreak lasted 7 weeks. At facility B, 90 case patients among 855 residents (11%) were identified (median age, 88 years) and 19 (21%) were hospitalized. The facility B outbreak lasted 9.3 weeks. Ill employees were identified at both locations. In each facility, attack rates seemed to differ by residential setting, with the lowest rates among those in more separated settings or with high baseline level of infection control measures. The causative genotype for both outbreaks was G2P[4]. Some individuals shed virus detected by enzyme immunoassay or genotyping reverse transcription polymerase chain reaction for at least 35 days. G2P[4] was also identified in 17 of 19 (89%) samples from the older adult community but only 15 of 40 (38%) pediatric samples.

Limitation: Medical or cognitive impairment among residents limited the success of some interviews.

Conclusion: Rotavirus outbreaks can occur among elderly adults in residential facilities and can result in considerable morbidity. Among older adults, G2P[4] may be of unique importance. Health professionals should consider rotavirus as a cause of acute gastroenteritis in adults.

Primary Funding Source: None.
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http://dx.doi.org/10.7326/0003-4819-157-9-201211060-00006DOI Listing
November 2012

Characterization of in vivo anti-rotavirus activities of saponin extracts from Quillaja saponaria Molina.

Antiviral Res 2011 Jun 23;90(3):231-41. Epub 2011 Apr 23.

The University of Texas Arlington, Department of Biology, Arlington, TX 76019, USA.

Rotavirus is the leading cause of severe diarrhea disease in newborns and young children worldwide with approximately 300,000 pre-adolescent deaths each year. Quillaja saponins are a natural aqueous extract obtained from the Chilean soapbark tree. The extract is approved for use in humans by the FDA for use in beverages as a food addictive. We have demonstrated that Quillaja extracts have strong antiviral activities in vitro against six different viruses. In this study, we evaluated the in vivo antiviral activity of these extracts against rhesus rotavirus (RRV) using a mouse model. We established that at a dosage of 0.015 mg/mouse of saponin extract, RRV induced diarrhea can be significantly reduced from 79% to 11% when mice are exposed to 500 plaque-forming-units (PFU) for each of five consecutive days. Additionally, while a reduction of RRV induced diarrhea depended both on the concentration of virus introduced and on the amount of Quillaja extract given to each mouse, the severity and interval of diarrhea under a variety of conditions tested, in all the treated mice were greatly reduced when compared to those that did not receive the Quillaja extracts. Mechanistically, there is strong evidence that the Quillaja extracts are able to "block" rotavirus infection by inhibiting virus-host attachment through disruption of cellular membrane proteins and/or virus receptors. We believe that Quillaja extracts have promise as antivirals to reduce rotavirus infection and the severity of the disease in humans.
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http://dx.doi.org/10.1016/j.antiviral.2011.04.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3106224PMC
June 2011

Prevention of rotavirus infections in vitro with aqueous extracts of Quillaja Saponaria Molina.

Future Med Chem 2010 Jul;2(7):1083-97

University of Texas at Arlington, Department of Biology, Arlington, TX 76010, USA.

Background: Rotavirus is the leading cause of severe diarrhea disease in newborns and young children worldwide, estimated to be responsible for over 300,000 childhood deaths every year, mostly in developing countries. Rotavirus-related deaths represent approximately 5% of all deaths in children younger than 5 years of age worldwide. Saponins are readily soluble in water and are approved by the US FDA for inclusion in beverages intended for human consumption. The addition of saponins to existing water supplies offers a new form of intervention into the cycle of rotavirus infection. We believe that saponins will 'coat' the epithelium of the host's small intestine and prevent attachment of rotavirus.

Discussion: This experiment provides in vitro data for the possibility of including saponin in drinking water to prevent infections of rotavirus. We demonstrate that microgram amounts of extract, while exhibiting no cell cytotoxicity or direct virucidal activity, prevent rotavirus from infecting its host cells. In addition, the presence of residual amounts of extract continue to block viral infection and render cells resistant to infection for at least 16 h after the removal of the extract from the cell culture media.

Conclusion: We demonstrate that two Quillaja extracts possess strong antiviral activity at concentrations more than 1000-fold lower than concentrations exhibiting cell cytotoxicity. Extract concentrations as high as 1000 μg/ml are not cytotoxic, but concentrations as low as 1.0 μg/ml are able to block rotavirus and reovirus attachment and infection.
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http://dx.doi.org/10.4155/fmc.10.206DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2921663PMC
July 2010
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