Papers by Juan Jose Amador Velazquez
International Journal of Environmental Research and Public Health, 2021
An ongoing epidemic of chronic kidney disease of uncertain etiology (CKDu) afflicts large parts o... more An ongoing epidemic of chronic kidney disease of uncertain etiology (CKDu) afflicts large parts of Central America and is hypothesized to be linked to heat stress at work. Mortality rates from CKDu appear to have increased dramatically since the 1970s. To explore this relationship, we assessed trends in maximum and minimum temperatures during harvest months between 1973 and 2014 as well as in the number of days during the harvest season for which the maximum temperature surpassed 35 °C. Data were collected at a weather station at a Nicaraguan sugar company where large numbers of workers have been affected by CKDu. Monthly averages of the daily maximum temperatures between 1996 and 2014 were also compared to concurrent weather data from eight Automated Surface Observing System Network weather stations across Nicaragua. Our objectives were to assess changes in temperature across harvest seasons, estimate the number of days that workers were at risk of heat-related illness and compare ...
International Journal of Environmental Research and Public Health, 2021
An ongoing epidemic of chronic kidney disease of uncertain etiology (CKDu) afflicts large parts o... more An ongoing epidemic of chronic kidney disease of uncertain etiology (CKDu) afflicts large parts of Central America and is hypothesized to be linked to heat stress at work. Mortality rates from CKDu appear to have increased dramatically since the 1970s. To explore this relationship, we assessed trends in maximum and minimum temperatures during harvest months between 1973 and 2014 as well as in the number of days during the harvest season for which the maximum temperature surpassed 35 °C. Data were collected at a weather station at a Nicaraguan sugar company where large numbers of workers have been affected by CKDu. Monthly averages of the daily maximum temperatures between 1996 and 2014 were also compared to concurrent weather data from eight Automated Surface Observing System Network weather stations across Nicaragua. Our objectives were to assess changes in temperature across harvest seasons, estimate the number of days that workers were at risk of heat-related illness and compare ...
The American Journal of Tropical Medicine and Hygiene, 2019
These tables present the results of the logisti regression models examining the assoiiaton betwee... more These tables present the results of the logisti regression models examining the assoiiaton between Leptospira seropositvity and presumptve esoameriian nephropathy status. They iorrespond to the paragraph just above the "Hantavirus serology" heading in the Results seiton of the paper. Abbreviatons of variables in models Variable name Description Values CLAS2 Case/iontrol status 0=iontrol, 1=iase AGE Age in years AGESQUARED Age in years squared SEXCODE Sex 0=male, 1=female 1 Ever worked in mining or ionstruiton 0=no, 1=yes NOT 1 Ever worked in mining or ionstruiton 0=yes, 1=no YRS Number of years worked in mining or ionstruiton LEPTO2 Seropositve for any tested strain of Leptospira 0=no, 1=yes 1*LEPTO2 Interaiton term NOT 1*LEPTO2 Interaiton term
The American Journal of Tropical Medicine and Hygiene, 2000
As part of an investigation of a 1995 outbreak of leptospirosis in Nicaragua, a cross-sectional s... more As part of an investigation of a 1995 outbreak of leptospirosis in Nicaragua, a cross-sectional serologic survey was conducted in the town of El Sauce. Of 566 persons, 85 (15%) were positive for IgM anti-Leptospira antibodies, indicating recent leptospirosis infection. Asymptomatic leptospirosis infection was common, with only 25 (29.4%) of the 85 seropositive inhabitants reporting a febrile illness in the 2 months before the survey. Multivariable analysis revealed that having an indoor water source remained independently protective against leptospirosis. Gathering wood was independently associated with infection. These findings suggest that asymptomatic infection with Leptospira is common in endemic areas of Leptospira transmission. Improvement in water sanitation and behavioral modifications to reduce environmental exposure may reduce the risk of leptospirosis in endemic regions.
Prehospital and Disaster Medicine, 2000
BMC Research Notes, 2015
Background: During an October 2005 algal bloom (i.e., a rapid increase or accumulation in the pop... more Background: During an October 2005 algal bloom (i.e., a rapid increase or accumulation in the population of algae) off the coast of Nicaragua, 45 people developed symptoms of paralytic shellfish poisoning (PSP) and one person died. PSP in humans is caused by ingestion of saxitoxin, which is a neurotoxin often associated with shellfish contaminated by algal blooms. To explore the relationship between the algal bloom and human illnesses, we performed a case-control study of residents living in a coastal island. We administered a standardized clinical questionnaire, sampled locally harvested seafood and algae, and obtained urine samples for saxitoxin testing from symptomatic and asymptomatic persons. PSP case-patients were defined as island residents who developed at least one neurological symptom during the November 4-16 intoxication period. Seafood and algal samples were analyzed for saxitoxins using the receptor-binding assay and high-performance liquid chromatography. Two urine samples were analyzed for saxitoxins using a newly developed immunoassay. Findings: Three shellfish and two algal samples tested positive for saxitoxins. Ten (9%) of 107 participants developed neurological symptoms during the specified time period and five required hospitalization. While 6 (67%) of 9 possible case-patients and 21 (21%) of 98 controls had eaten fish (p=0.008), all case-patients and 17 (17%) of controls had eaten clams (P<0.0001). The saxitoxin concentration in the urine of a hospitalized case-patient was 21 ng saxitoxin/g creatinine compared to 0.16 ng saxitoxin/g creatinine in the single control patient's urine. Conclusions: These findings suggest that a bloom of saxitoxin-producing algae resulted in saxitoxin accumulation in local clams and was responsible for the PSP intoxication.
International journal of gynecological cancer : official journal of the International Gynecological Cancer Society, 2014
This study evaluates the feasibility and performance of careHPV, a novel human papillomavirus (HP... more This study evaluates the feasibility and performance of careHPV, a novel human papillomavirus (HPV) DNA test, when used for screening women for cervical cancer in low-resource settings. Clinician-collected (cervical) and self-collected (vaginal) careHPV specimens, visual inspection with acetic acid (VIA), and Papanicolaou test were evaluated among 16,951 eligible women in India, Nicaragua, and Uganda. Women with positive screening results received colposcopy and histologic follow-up as indicated. The positivity of each screening method was calculated overall, by site, and age. In addition, the clinical performance of each screening test was determined for detection of cervical intraepithelial neoplasia (CIN) grade 2 (CIN2+) and CIN grade 3. Moderate or severe dysplasia or cancer (taken together as CIN2+) was diagnosed in 286 women. The positivity rate ranged between 2.4% to 19.6% for vaginal careHPV, 2.9% to 20.2% for cervical careHPV, 5.5% to 34.4% for VIA, and 2.8% to 51.8% for Pa...
Tropical Medicine and International Health, 2006
To investigate the incidence of dengue virus (DENV) infection in Nicaragua, a 2-year prospective ... more To investigate the incidence of dengue virus (DENV) infection in Nicaragua, a 2-year prospective study was conducted in schoolchildren 4-16 years old in the capital city of Managua. Blood samples were collected before the rainy season in 2001, 2002 and 2003, and were assayed for DENV-specific antibodies. Participants were monitored for dengue-like illness, and acute and convalescent blood samples were collected from suspected dengue cases. In 2001 and 2002, 602 and 397 students were recruited, respectively, and paired annual serum samples were available from 467 and 719 participants in 2001-2002 and 2002-2003, respectively. The overall seroprevalence of anti-DENV antibodies was 91%, increasing from 75% at age 4 to 100% at age 16. The incidence of DENV infection was 12% in Year 1 and 6% in Year 2 (P < 0.001). During Year 1, four laboratory-confirmed dengue cases were detected, with one DENV2 isolate; during Year 2, there were six confirmed dengue cases, with one DENV1 isolate. These and additional circulating serotypes were confirmed by plaque reduction neutralisation test. This study demonstrates surprisingly high transmission of DENV in urban Nicaragua.
Revista Panamericana de Salud Pública, 2008
Objectives. We investigated a nationwide outbreak of severe rotavirus gastroenteritis in Nicaragu... more Objectives. We investigated a nationwide outbreak of severe rotavirus gastroenteritis in Nicaragua in children under 5 years old, leading to many consultations, hospitalizations, and deaths. We questioned whether a vaccine might have prevented these illnesses and deaths, sought to identify risk factors for death, and developed a clinical profile of children hospitalized with diarrhea. Methods. We conducted a case-control study to determine whether children who died had access to routine immunizations, a proxy predicting access to a rotavirus vaccine. We identified risk factors for death among children who died in the outbreak compared with surviving age-matched controls with diarrhea. We collected stools, clinical data, and immunization data on children hospitalized for diarrhea to test for rotavirus, develop the profile, and forecast future access to a rotavirus vaccine. Results. The outbreak from February to April 2005 caused 47 470 consultations and 52 deaths. Approximately 80% of cases and controls and 60% of children hospitalized with diarrhea had access to routine immunizations and would likely have had access to a rotavirus vaccine. With a vaccine efficacy of 85%, up to 51% of severe rotavirus cases and up to 68% of deaths could have been prevented if a rotavirus vaccine were available as part of routine childhood immunizations. Study of 35 case-control pairs indicated that severe illnesses, malnutrition, and care by traditional healers were risk factors for death. Rotavirus was found in 42% of samples from hospitalized children and was associated with severe disease and dehydration. Conclusions. The impact of the seasonal outbreaks of rotavirus disease could be diminished with a rotavirus vaccine, improvements in oral rehydration programs, and training of traditional healers in the proper management of children with acute diarrhea.
The Journal of Infectious Diseases, 1998
The CDC policy with regard to human subjects review during investigation of an acute health probl... more The CDC policy with regard to human subjects review during investigation of an acute health problem in a community were adhered to.
The Journal of Infectious Diseases, 2009
Background. In October 2006, a new rotavirus vaccine was introduced in Nicaragua and was availabl... more Background. In October 2006, a new rotavirus vaccine was introduced in Nicaragua and was available free to all age-eligible children. We assessed vaccine uptake and trends in acute gastroenteritis (AGE) to assess vaccine impact. Methods. We analyzed national data from the period 2001-2007 on the total number of AGE episodes and on RotaTeq vaccine dose administration during 2006-2007. Results. After the introduction of RotaTeq, 1-dose vaccine coverage rates rapidly increased to 80% among age-eligible children. During the 2007 rotavirus season, when combined 2-and 3-dose vaccine coverage among children aged 0-11 months was ∼26%, the total number of AGE episodes among children aged 0-11 months decreased by 23%, compared with a decrease of 6% among unvaccinated children aged 12-59 months. Furthermore, a 12% decrease in the number of all-cause hospitalizations for AGE was noted among children aged 0-11 months, whereas a ∼5% increase was observed among children aged 12-59 months. Conclusions. The high rate of vaccination among age-eligible children soon after vaccine introduction in Nicaragua indicates an efficient immunization program. However, in the age group at risk of rotavirus disease, vaccine coverage during the 2007 rotavirus season had yet to reach a level sufficient for making firm conclusions about vaccine impact. Epidemiologic studies to evaluate vaccine effectiveness and ongoing surveillance as vaccine uptake increases will allow a better assessment of vaccine impact. Rotavirus is the most common cause of severe gastroenteritis in children !5 years of age worldwide, accounting for an estimated 2.4 million hospital admissions and 527,000 deaths each year [1, 2]. Because of the tremendous global burden of rotavirus, vaccine introduction has been a high priority for several international agencies, including the World Health Organization and the GAVI Alliance (formerly known as the Potential conflicts of interest: none reported.
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Journal of Clinical Microbiology, 2007
During February and March 2005, one of the largest national recorded outbreaks of severe acute ga... more During February and March 2005, one of the largest national recorded outbreaks of severe acute gastroenteritis occurred in Nicaragua, affecting ≥64,000 individuals and causing ≥56 deaths, predominantly in children under 5 years of age. Through a nationwide laboratory-based study, stool samples were collected and investigated for rotavirus. Of 108 stool samples examined, 72 (67%) were positive for rotavirus. While 69% (50/72) of the positive samples were found in children less than 2 years of age, 50% (6/12) of the adult samples were positive. A mutated G4P[8] strain was the most commonly recognized strain (85%), followed by mixed G strains (8%) and G9P[8] (7%) strains. Phylogenetic analysis of the VP7 gene revealed that the G4 strains belonged to the emerging lineage Ic and was distantly related to the ST3 and VA70 G4 strains. Secondary structure predictions of the VP7 G4 protein revealed an insert of an asparagine residue in position 76, which, combined with additional mutations, s...
International Journal of Infectious Diseases, 2010
Background: In October 2006, a rotavirus vaccine was introduced in Nicaragua for routine immuniza... more Background: In October 2006, a rotavirus vaccine was introduced in Nicaragua for routine immunization of all children. We document the baseline diarrheal disease burden in Nicaragua prior to the vaccine program to facilitate future studies to measure vaccine impact. Methods: We analyzed national data for 2001-2005 on total acute gastroenteritis healthcare visits, hospitalizations, and mortality in Nicaraguan children aged <5 years. Results: Prior to vaccine introduction, by age 5 years, one in four Nicaraguan children required an outpatient consultation, one in 34 were hospitalized, and one in 2487 died from rotavirus-associated diarrhea, representing approximately 41 122 outpatient visits, 4460 hospitalizations, and 60 deaths per year that are preventable through vaccination. Almost half of the total acute gastroenteritis burden was in children <1 year of age. Two distinct seasonal peaks were noted in acute gastroenteritis hospitalizations and deaths. Conclusions: Existing data sources on all-cause acute gastroenteritis could be useful for establishing diarrhea disease burden and monitoring trends after vaccine introduction. Blunting of winter season peaks in rates of diarrhea, particularly among children aged <1-2 years, would be a useful indicator of impact from rotavirus vaccination.
Human Vaccines, 2010
Edelman (2010) Dengue vaccine trial guidelines and role of large-scale, post proof-of-concept dem... more Edelman (2010) Dengue vaccine trial guidelines and role of large-scale, post proof-of-concept demonstration projects in bringing a dengue vaccine to use in dengue endemic areas,
Emerging Infectious Diseases, 2003
In a hospital and health center-based study in Nicaragua, fluid intake during the 24 hours before... more In a hospital and health center-based study in Nicaragua, fluid intake during the 24 hours before being seen by a clinician was statistically associated with decreased risk for hospitalization of dengue fever patients. Similar results were obtained for children <15 years of age and older adolescents and adults in independent analyses.
Bulletin of the World Health Organization, 2011
Journal of Epidemiology and Community Health, 2012
For almost 2 decades, large areas of Central America have been impacted by an under-recognised ep... more For almost 2 decades, large areas of Central America have been impacted by an under-recognised epidemic of chronic kidney disease (CKD) of unknown causes whose victims are disproportionately young men of working age.1–5 Although exact figures are unavailable, based on estimates from our group, the death toll has likely reached at least 20 000. El Salvador, for example, has the highest overall mortality from kidney disease in the world (with Nicaragua and Honduras also included in the 10 highest countries), and CKD is the second leading cause of mortality among men of working age in the country.4 ,6 Furthermore, similar excesses of CKD of unknown cause have been reported in Sri Lanka,7 India8 and Egypt,9 where many of the epidemiological characteristics appear to be similar to the epidemic in Central America. Despite its scientific and public health importance and its potential global reach, we have found that most health researchers and public health practitioners are unaware of this epidemic. Our goal in this editorial is to provide a brief overview of the epidemiological, aetiological and public health dimensions of the epidemic. We are part of a multidisciplinary and multinational team of researchers whose involvement began in 2009 when we were selected to conduct research to search for the cause(s) of excess CKD by the participants of a mediation process managed by the Compliance Advisor/Ombudsman Office, an independent recourse mechanism for the World Bank10 aimed at responding to complaints from project-affected communities with the goal of providing a mechanism for representatives of the communities to sit at the table with recipients of World Bank private sector loans and address issues raised in the complaints. The participants included a sugar cane company in Nicaragua and a group of more than 2000 sick ex-workers and their families. During …
American Journal of Kidney Diseases, 2016
Estudio descriptivo de la epidemiologia de la rabia, a fin de contribuir en la restructuracion de... more Estudio descriptivo de la epidemiologia de la rabia, a fin de contribuir en la restructuracion de estrategias y toma de decisiones para el control de la rabia en el pais; durante el periodo 1967-1983 se obtuvo informacion de fuentes secundarias. Se encontro que anualmente se registraron un promedio de 160 animales rabiosos de los que 140 son perros, 7 gatos, 6 bovinos y algunos de vida salvaje. Los animales mordedores predominantes son el perro y el vampiro. La mortalidad humana mas frecuente fue en ninos y en el sexo masculino. Las actividades de control de la rabia canina se han realizado hasta porcentajes de cobertura muy inferior a lo recomendado por los expertos de la OMS, y lo referido en las normas; los anos 1980 y 1983 han sido los que registran los mejores porcentajes de vacunacion con el apoyo de organizaciones de masas. En 5 de 16 muertes del periodo 1979-1983 se conocio que acudieron a los Centros de Salud, despues de haber sido mordidos por perros rabiosos y en el 100 porciento se dio mal manejo a los mismos, los restantes 11 de 16 se registraron; conociendose el problema hasta que aparecio el cuadro clinico de la enfermedad.
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Papers by Juan Jose Amador Velazquez