Umesh D Parashar

Christian Medical College & Hospital, Ludhiana, Punjab, India

Are you Umesh D Parashar?

Claim your profile

Publications (371)2373.93 Total impact

  • The Journal of infectious diseases. 06/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To examine reductions in diarrhea-associated health care utilization after rotavirus vaccine implementation and to assess direct and indirect effectiveness of vaccination.METHODS: Retrospective cohort analysis of claims data of commercially insured US children aged <5 years. We examined annual pentavalent (RV5) and monovalent (RV1) rotavirus vaccine coverage. We compared rates of diarrhea-associated health care utilization in prevaccine (2001-2006) versus postvaccine introduction (2007-2011) years, compared rates of diarrhea-associated health care utilization in vaccinated versus unvaccinated children and compared rates in unvaccinated children in postvaccine versus prevaccine years.RESULTS: Among children aged <5 years, RV5 and RV1 rotavirus vaccine coverage rates reached 58% and 5%, respectively, by December 31, 2010. Compared with the average rate of rotavirus-coded hospitalizations in 2001-2006, rates were reduced by 75% in 2007-2008, 60% in 2008-2009, 94% in 2009-2010, and 80% in 2010-2011. Compared with unvaccinated children, in 2010-2011, the rate of rotavirus-coded hospitalizations was reduced by 92% among RV5 recipients and 96% among RV1 recipients. Rotavirus-coded hospitalization rate reductions among RV5 recipients versus unvaccinated children ranged from 87% among <1-year-olds to 81% among 4-year-olds. Compared with prevaccine rates in 2001-2006, rotavirus-coded hospitalization rates among unvaccinated children decreased by 50% in 2007-2008, 77% in 2009-2010, and 25% in 2010-2011.CONCLUSIONS: Implementation of rotavirus vaccines has substantially reduced diarrhea health care utilization in US children. Both rotavirus vaccines conferred high protection against rotavirus hospitalizations; RV5 conferred durable protection through the fourth year of life. Vaccination also conferred indirect benefits to unvaccinated children.
    PEDIATRICS 06/2014; · 4.47 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Introduction: Norovirus is the leading cause of acute gastroenteritis and foodborne disease in the United States, causing an estimated one in 15 U.S. residents to become ill each year as well as 56,000-71,000 hospitalizations and 570-800 deaths, predominantly among young children and the elderly. Whereas noroviruses often spread through person-to-person contact, foodborne transmission can cause widespread exposures and presents important prevention opportunities.
    MMWR. Morbidity and mortality weekly report. 06/2014; 63(22):491-495.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Norovirus infections are notoriously difficult to prevent and control due to their low infectious dose, high shedding titer, and environmental stability. The virus can spread through multiple transmission routes of which person-to-person and foodborne are the most important. Recent advances in molecular diagnostics, have helped to establish norovirus as the most common cause of sporadic gastroenteritis and most common cause of outbreaks of acute gastroenteritis across all ages. In this paper, we review the epidemiology and virology of noroviruses as well as prevention and control guidelines with a focus on the principles of disinfection and decontamination; Outbreak management relies on sound infection control principles including hand hygiene, limiting exposure to infectious individuals, and thorough environmental decontamination. Ideally, all infection control recommendations would rely on empirical evidence, but a number of challenges, including the inability to culture norovirus in the laboratory and the challenges of outbreak management in complex environments, has made it difficult to garner clear evidence of efficacy in certain areas of infection control. New experimental data on cultivable surrogates for human norovirus on the environmental survivability and relative resistance to commonly used disinfectants, are providing new insights in further refining disinfection practices. Finally, clinical trials are underway to evaluate the efficacy of vaccines which may shift the current infection control principles to more targeted interventions.This article is protected by copyright. All rights reserved.
    Clinical Microbiology and Infection 05/2014; · 4.58 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Rotavirus is the leading cause of severe diarrhea among children<5 years worldwide. Currently licensed rotavirus vaccines have been efficacious and effective, with many countries reporting substantial declines in diarrheal and rotavirus-specific morbidity and mortality. However, the full public health impact of these vaccines has not been realized. Most countries, including those with the highest disease burden, have not yet introduced rotavirus vaccines into their national immunization programs. Research activities that may help inform vaccine introduction decisions include (1) establishing effectiveness, impact, and safety for rotavirus vaccines in low-income settings; (2) identifying potential strategies to improve performance of oral rotavirus vaccines in developing countries, such as zinc supplementation; and (3) pursuing alternate approaches to oral vaccines, such as parenteral immunization. Policy- and program-level barriers, such as financial implications of new vaccine introductions, should be addressed to ensure that countries are able to make informed decisions regarding rotavirus vaccine introduction.
    Human vaccines & immunotherapeutics. 04/2014; 10(6).
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To investigate the effect of abstention from breastfeeding, for an hour before and after each vaccination, on the immune responses of infants to two doses of rotavirus vaccine. In Soweto, South Africa, mother-infant pairs who were uninfected with human immunodeficiency virus (HIV) were enrolled as they presented for the "6-week" immunizations of the infants. Each infant was randomly assigned to Group 1 - in which breastfeeding was deferred for at least 1 h before and after each dose of rotavirus vaccine - or Group 2 - in which unrestricted breastfeeding was encouraged. Enzyme-linked immunosorbent assays were used to evaluate the titres of rotavirus-specific IgA in samples of serum collected from each infant immediately before each vaccine dose and 1 month after the second dose. Among the infants, a fourfold or greater increase in titres of rotavirus-specific IgA following vaccination was considered indicative of seroconversion. The evaluable infants in Group 1 (n = 98) were similar to those in Group 2 (n = 106) in their baseline demographic characteristics and their pre-vaccination titres of anti-rotavirus IgA. After the second vaccine doses, geometric mean titres of anti-rotavirus IgA in the sera of Group-1 infants were similar to those in the sera of Group-2 infants (P = 0.685) and the frequency of seroconversion in the Group-1 infants was similar to that in the Group-2 infants (P = 0.485). Among HIV-uninfected South African infants, abstention from breastfeeding for at least 1 h before and after each vaccination dose had no significant effect on the infants' immune response to a rotavirus vaccine.
    Bulletin of the World Health Organisation 04/2014; 92(4):238-45. · 5.25 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To assess the effectiveness of the monovalent rotavirus vaccine (RV1) to prevent rotavirus diarrhea admissions to emergency departments (ED) in Colombia. A multicenter case-control study was carried out in six Colombian cities from 2011 to January, 2013. Cases were laboratory confirmed rotavirus diarrhea patients admitted to ED of selected health centers. Controls were patients with non-rotavirus diarrhea. Vaccination status was card-confirmed. Vaccine effectiveness and 95% confidence intervals (CI) were calculated from the conditional logistic regression models using the formula 1-adjusted odds ratio×100. 1051 fecal samples were collected from 193 cases and 858 controls. Vaccination history was confirmed on 173 cases (90%) and 801 controls (93%). Among the rotavirus-positive samples with vaccination history, 57% were G2P[4], 9.8% G9P[8], 6% G9P[6]. Median age of cases (17 months) was greater than controls (15 months) (P<0.001), and mothers of cases had lower level of education (P=0.025). The adjusted effectiveness was 79.19% (95% CI, 23.7 to 94.32) among children 6-11 months of age and -39.75% (95% CI, -270.67 to 47.24) among those >12 months of age. Against overnight rotavirus hospitalizations, RV1 provided protection of 84.42% (95% CI, 22.68 to 96.86) among children 6-11 months of age, and -79.49% (95% CI, -555.8 to 51.08) among those >12 months. RV1 provided significant protection against rotavirus hospitalization among children under 1 year of age in the Colombian setting. The observation of lower effectiveness in children >12 months requires further assessment.
    Vaccine 03/2014; · 3.77 Impact Factor
  • Shabir A Madhi, Umesh D Parashar
    The Lancet 03/2014; · 39.21 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Two rotavirus (RV) vaccines (Rotarix and RotaTeq) are available on the private market in Taiwan, but are not recommended for routine use. We examined RV vaccine effectiveness (VE) against severe RV acute gastroenteritis (AGE) among Taiwanese infants to inform policymakers on the potential benefits of national RV vaccine introduction. From May 2009 to April 2011, a case-control assessment of VE against severe RV AGE was conducted at 3 hospital-based surveillance sites in Taiwan. Case-patients included children aged 8-35 months, hospitalized with laboratory-confirmed RV AGE. Controls included children age-matched within 1 month of age of the case-patient, hospitalized with RV-negative AGE or seen for non-AGE illnesses at the same hospitals. Vaccination history was confirmed through vaccination card or hospital record review. VE was calculated as (1 - odds ratio of vaccination)×100%. We enrolled 184 case-patients with RV AGE, 904 RV-negative AGE and 909 non-AGE controls. Two-dose Rotarix series VE against RV gastroenteritis hospitalization was 90.4% [95% confidence interval (CI): 70.3%, 98.1%) and 92.5% (95% CI: 77.1%, 98.5%) with RV-negative AGE and non-AGE controls, respectively. Three-dose RotaTeq series VE was 96.8% (95% CI: 82.3%, 100%) and 97.1% (95% CI: 84%, 100%) with RV-negative AGE and non-AGE controls, respectively. Both vaccines provided excellent protection against severe RV AGE hospitalization. Addition of RV vaccination into Taiwan's National Immunization Program could substantially decrease AGE hospitalizations among children <3 years. Our findings should help inform policymakers in Taiwan and other similar Asian countries when deciding whether to include RV vaccination into their national immunization programs.
    The Pediatric Infectious Disease Journal 03/2014; 33(3):e81-6. · 3.57 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In many GAVI-eligible countries, effectiveness of new vaccines will be evaluated by case-control methodology. To inform the design and assess selection bias of a future case-control study of rotavirus vaccine effectiveness (VE) in western Kenya, we performed a sham case-control study evaluating VE of pentavalent vaccine (DTP-Hib-HepB) against rotavirus acute gastroenteritis (AGE). From ongoing rotavirus surveillance, we defined cases as children 12 weeks to 23 months old with EIA-confirmed rotavirus AGE. We enrolled one community-based and two hospital-based control groups. We collected vaccination status from cards at enrollment, or later in homes, and evaluated VE by logistic regression. We enrolled 91 cases (64 inpatient, 27 outpatient), 252 non-rotavirus AGE facility-based controls (unmatched), 203 non-AGE facility-based controls (age-matched) and 271 community controls (age-matched). Documented receipt of 3 pentavalent doses was 77% among cases and ranged from 81-86% among controls. One percent of cases and 0-2% of controls had no pentavalent doses. The adjusted odds ratio of three versus zero doses for being a case was 3.27 (95% CI 0.01-1010) for community controls and 0.69 (95% CI 0.06-7.75) for non-rotavirus hospital-based AGE controls, translating to VE of -227% and 31%, respectively, with wide confidence intervals. (No facility-based non-AGE controls were unvaccinated.) Similar results were found for >=2 pentavalent doses and for severe rotavirus AGE. The study showed that it is feasible to carry out a real case control in the study area, but this needs to be done as soon as the vaccine is introduced to capture the real impact. Sham case-control or pilot studies before vaccine introduction can be useful in designing case-control VE studies.
    BMC Infectious Diseases 02/2014; 14(1):77. · 3.03 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Objective To investigate the effect of abstention from breastfeeding, for an hour before and after each vaccination, on the immune responses of infants to two doses of rotavirus vaccine. Methods In Soweto, South Africa, mother–infant pairs who were uninfected with human immunodeficiency virus (HIV) were enrolled as they presented for the “6-week” immunizations of the infants. Each infant was randomly assigned to Group 1 – in which breastfeeding was deferred for at least 1 h before and after each dose of rotavirus vaccine – or Group 2 – in which unrestricted breastfeeding was encouraged. Enzyme-linked immunosorbent assays were used to evaluate the titres of rotavirus-specific IgA in samples of serum collected from each infant immediately before each vaccine dose and 1 month after the second dose. Among the infants, a fourfold or greater increase in titres of rotavirus-specific IgA following vaccination was considered indicative of seroconversion. Findings The evaluable infants in Group 1 (n = 98) were similar to those in Group 2 (n = 106) in their baseline demographic characteristics and their pre-vaccination titres of anti-rotavirus IgA. After the second vaccine doses, geometric mean titres of anti-rotavirus IgA in the sera of Group-1 infants were similar to those in the sera of Group-2 infants (P = 0.685) and the frequency of seroconversion in the Group-1 infants was similar to that in the Group-2 infants (P = 0.485). Conclusion Among HIV-uninfected South African infants, abstention from breastfeeding for at least 1 h before and after each vaccination dose had no significant effect on the infants’ immune response to a rotavirus vaccine.
  • [Show abstract] [Hide abstract]
    ABSTRACT: To assess, by socioeconomic setting, the effect of nationwide vaccination against species A rotavirus (RVA) on childhood diarrhoea-related hospitalizations in Mexico. Data on children younger than 5 years who were hospitalized for diarrhoea in health ministry hospitals between 1 January 2003 and 31 December 2011 were collected from monthly discharge reports. Human development indexes were used to categorize the states where hospitals were located as having generally high, intermediate or low socioeconomic status. Annual rates of hospitalization for diarrhoea - per 10 000 hospitalizations for any cause - were calculated. Administrative data were used to estimate vaccine coverage. In the states with high, intermediate and low socioeconomic status, coverage with a two-dose monovalent RVA vaccine - among children younger than 5 years - had reached 93%, 86% and 71%, respectively, by 2010. The corresponding median annual rates of hospitalization for diarrhoea - per 10 000 admissions - fell from 1001, 834 and 1033 in the "prevaccine" period of 2003-2006, to 597, 497 and 705 in the "postvaccine" period from 2008 to 2011, respectively. These decreases correspond to rate reductions of 40% (95% confidence interval, CI: 38-43), 41% (95% CI: 38-43) and 32% (95% CI: 29-34), respectively. Nationwide, RVA vaccination appeared to have averted approximately 16 500 hospitalizations for childhood diarrhoea in each year of the postvaccine period. Monovalent RVA vaccination has substantially reduced childhood diarrhoea-related hospitalizations for four continuous years in discretely different socioeconomic populations across Mexico.
    Bulletin of the World Health Organisation 02/2014; 92(2):117-25. · 5.25 Impact Factor
  • Roger I Glass, Umesh D Parashar
    [Show abstract] [Hide abstract]
    ABSTRACT: In January 2006, the Journal published two landmark articles reporting the safety and efficacy of two different vaccines - RotaTeq (Merck), a pentavalent vaccine (RV5)(1) and Rotarix (GlaxoSmithKline), a monovalent vaccine (RV1)(2) - to prevent rotavirus, the most common cause of severe childhood diarrhea worldwide and of deaths from diarrhea in low-income countries. Each trial enrolled more than 60,000 infants to determine whether these live oral vaccines caused intussusception, the rare complication that in 1999 forced the withdrawal of the first licensed rotavirus vaccine, RotaShield (Wyeth Lederle), less than a year after it was recommended for routine immunization of U.S. . . .
    New England Journal of Medicine 01/2014; · 54.42 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Prior to the introduction of rotavirus vaccines in 2006, rotavirus was the leading cause of severe gastroenteritis among US children <5 years of age. In the first 7 years of vaccine use, both recommended rotavirus vaccines (RotaTeq [RV5] and Rotarix [RV1]) have been shown to be highly effective in preventing outcomes of severe disease in US children in a variety of settings. In addition, substantial decreases in severe diarrheal disease in US children, exceeding the level expected based on vaccine coverage, as well as the extension of benefits to older age groups ineligible for vaccination have demonstrated both the direct and indirect impacts of vaccination in the USA.
    Expert Review of Vaccines 01/2014; · 4.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Rotavirus gastroenteritis is a major cause of mortality among children <2 years of age. Disease burden data are important for introducing and sustaining new rotavirus vaccines in immunization programs. We analyzed population-based infectious disease surveillance data from 2007 to 2010 from Kenyan sites in rural and urban slum areas. Stool specimens were collected from patients of all ages presenting to study clinics with diarrheal disease and tested for rotavirus by enzyme immunoassay. Incidence rates were adjusted using data on healthcare utilization (from biweekly home visits) and proportion of stools collected at study clinics from patients meeting case definitions. Rotavirus was detected in 285 (9.0%) of 3174 stools tested, including 122 (11.9%) from children <5 years of age and 162 (7.6%) from participants ≥5 years of age. Adjusted incidence rates for infants were 13,419 and 12,135 per 100,000 person-years of observation in rural and urban areas, respectively. Adjusted incidence rates were high in adults across age ranges. The rates suggest that annually, among children <5 years of age, there are >54,500 cases of rotavirus-associated gastroenteritis in rural Nyanza Province and >16,750 cases in Nairobi urban slums. Community-based surveillance in urban and rural Kenya suggests that rotavirus plays an important role as a cause of acute gastroenteritis in adults, as well as in children. In addition to substantially preventing illness and complications from diarrheal disease in children, rotavirus infant immunization has the potential of indirectly preventing diarrheal disease in older children and adults, assuming children are the predominant sources of transmission.
    The Pediatric Infectious Disease Journal 01/2014; 33 Suppl 1:S54-61. · 3.57 Impact Factor
  • Source
    Vaccine. 01/2014; 32:vii–xii.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Countries in Africa have begun introducing rotavirus vaccines in their national immunization programs, and wide-scale rollout across the continent is expected during the next few years. In preparation for vaccine introduction, many countries initiated surveillance for rotavirus and other studies to document disease burden, to describe the epidemiology and to monitor circulating rotavirus strains in Africa. In addition, 2 countries sought to systematically investigate cases of intussusception, a rare adverse event that has been associated with rotavirus vaccines in some settings. The ongoing surveillance provided data that will serve as a baseline against which the impact of rotavirus vaccines in Africa can be assessed.
    The Pediatric Infectious Disease Journal 01/2014; 33 Suppl 1:S1-5. · 3.57 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: With the imminent availability of new and prospective rotavirus vaccines, reliable information on burden of rotavirus diseases in the different African countries was required to enable evidence-based decision making regarding introduction of rotavirus vaccines. World Health Organization has been supporting Member States since 2006 to establish sentinel surveillance for rotavirus diarrhea in children <5 years of age using standardized guidelines. African countries are using this platform to generate high quality country specific data to document and demonstrate the burden of rotavirus gastroenteritis. The data gathered are being used by policy makers to guide decisions on appropriate intervention strategies for diarrhea control including the value and timing of the introduction of new rotavirus vaccines in the national immunization programs.
    The Pediatric Infectious Disease Journal 01/2014; 33 Suppl 1:S6-8. · 3.57 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: As rotavirus vaccine is introduced into routine childhood immunization programs in Africa, understanding its impact on diarrheal disease burden is important. The objective of this analysis was to determine whether routinely collected health information on national diarrhea hospitalizations, in-hospital deaths and outpatient visits would be useful to monitor rotavirus vaccine impact. We analyzed data for all-cause, nonbloody diarrheal disease among children <5 years of age from the routine health management information system (HMIS) in Rwanda from January 2008 through December 2011. We described trends in absolute numbers of inpatient admissions, in-hospital deaths and outpatient visits by year, age and setting. All-cause, nonbloody diarrheal hospitalizations and outpatient visits among children <5 years of age in Rwanda from 2008 to 2011 peaked during the June to August dry season, coinciding with the rotavirus season. The bulk of the diarrheal disease burden occurred in children <1 year of age. Health centers provided many care to children with diarrhea including 60-72% of hospitalizations and 97-99% of outpatient visits. Many in-hospital diarrheal deaths (84%) occurred in district hospitals. Given the stable and consistent trends and the prominent seasonality consistent with that of rotavirus, HMIS data should provide a useful baseline to monitor rotavirus vaccine impact on the overall diarrheal disease burden in Rwanda. Active, sentinel surveillance for rotavirus diarrhea will help interpret changes in diarrheal disease trends following vaccine introduction. Other countries planning rotavirus vaccine introduction should explore the availability and quality of their HMIS data.
    The Pediatric Infectious Disease Journal 01/2014; 33 Suppl 1:S89-93. · 3.57 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In 2011, Sudan became the first low-income country in Africa to introduce a rotavirus vaccine. Prevaccine baseline data on rotavirus disease burden are crucial for monitoring the impact of this new vaccine program. We conducted active, hospital-based surveillance for rotavirus disease at 8 regional public hospitals in Sudan using a standard protocol recommended by the World Health Organization for 2 full years immediately preceding vaccine introduction. Cases were children <5 years hospitalized with gastroenteritis, defined as acute onset of 3 or more loose stools or 2 or more episodes of vomiting in a 24-hour period. Stool specimens from cases were tested for rotavirus using a commercially available assay. From June 2009 to May 2011, rotavirus was detected in 3985 (36%) of 10,953 children hospitalized for gastroenteritis, with detection rates ranging from 25% to 48% at the 8 hospitals. Approximately 61% of the rotavirus hospitalizations occurred before 1 year of age and most (91%) occurred before 2 years of age. Rotavirus was detected year-round in Sudan with peaks during March to May and November to December. Applying rotavirus prevalence to national estimates of diarrhea events, we calculated 9800 deaths, 22,800 hospitalizations and 55,400 outpatient visits related to rotavirus per year among children <5 years of age in Sudan. The high burden of rotavirus disease in Sudan indicates that the recently implemented vaccination program should substantially improve child health in Sudan. This nationwide rotavirus surveillance system will be an important platform for assessing the benefits and value of rotavirus vaccine in a developing country setting.
    The Pediatric Infectious Disease Journal 01/2014; 33 Suppl 1:S23-7. · 3.57 Impact Factor

Publication Stats

11k Citations
2,373.93 Total Impact Points

Institutions

  • 2014
    • Christian Medical College & Hospital
      Ludhiana, Punjab, India
  • 1998–2014
    • Centers for Disease Control and Prevention
      • • Division of Viral Diseases
      • • National Center for Immunization and Respiratory Diseases
      • • National Center for Emerging and Zoonotic Infectious Diseases
      Atlanta, Michigan, United States
    • Centers for Disease Control, Lesotho
      Maseru, Maseru, Lesotho
    • University of Maryland, Baltimore
      • Center for Vaccine Development
      Baltimore, MD, United States
  • 2013
    • National Institute of Hygiene and Epidemiology
      Hà Nội, Ha Nội, Vietnam
    • National Institutes of Health
      Maryland, United States
    • University of the Valley of Guatemala
      • Center for Health Studies
      Guatemala City, Departamento de Guatemala, Guatemala
  • 2012
    • Hungarian Academy of Sciences
      • Institute for Veterinary Medical Research, MTA Centre for Agricultural Research
      Budapest, Budapest fovaros, Hungary
    • University of Illinois, Urbana-Champaign
      Urbana, Illinois, United States
    • University of Cape Town
      Kaapstad, Western Cape, South Africa
    • Highland Hospital
      Oakland, California, United States
    • Vanderbilt University
      Nashville, Michigan, United States
  • 2011–2012
    • Princeton University
      • Department of Ecology and Evolutionary Biology
      Princeton, New Jersey, United States
    • Center for Adolescent Health and the Law
      North Carolina, United States
    • National Institute of Infectious Diseases, Tokyo
      Edo, Tōkyō, Japan
    • University of Rochester
      • Department of Pediatrics
      Rochester, NY, United States
    • Cincinnati Children's Hospital Medical Center
      Cincinnati, Ohio, United States
  • 2010
    • PATH
      Seattle, Washington, United States
    • Ministerio de Salud, El Salvador
      San Salvador, San Salvador, El Salvador
    • Baylor College of Medicine
      Houston, Texas, United States
    • Texas Children's Hospital
      • Center for Vaccine Awareness and Research
      Houston, Texas, United States
  • 2009
    • National Autonomous University of Nicaragua, Managua
      Μανάγκουα, Managua, Nicaragua
    • University of Colorado
      • Department of Medicine
      Denver, CO, United States
    • University of Melbourne
      • Department of Paediatrics
      Melbourne, Victoria, Australia
    • Pennsylvania State University
      • Center for Infectious Disease Dynamics
      University Park, MD, United States
  • 1998–2009
    • Emory University
      • • Department of Global Health
      • • Department of Pediatrics
      Atlanta, Georgia, United States
  • 2008
    • Queen Mary Hospital
      Hong Kong, Hong Kong
  • 2005–2008
    • The Chinese University of Hong Kong
      • Department of Paediatrics
      Hong Kong, Hong Kong
  • 2001–2005
    • National Institute of Allergy and Infectious Diseases
      Maryland, United States
  • 2004
    • Department of Environment & Conservation, Tennessee
      Nashville, Tennessee, United States
  • 2001–2002
    • U.S. Department of Health and Human Services
      • Centers for Disease Control and Prevention (CDC)
      Washington, Washington, D.C., United States
  • 1999
    • Alpert Medical School - Brown University
      Providence, Rhode Island, United States