Transmission Patterns of Norovirus From Infected Children to Household Members in León, Nicaragua.

Norovirus is a common and highly transmissible gastrointestinal pathogen. Among 34 Nicaraguan households with a norovirus-infected child, 48% experienced norovirus transmission within 1 week, infecting 18% of household members; GII norovirus was more commonly transmitted than GI. Pediatric norovirus vaccines could prevent both index cases and transmission to close contacts.

Epidemiology of pediatric astrovirus gastroenteritis in a Nicaraguan birth cohort.

Background: Astrovirus is a leading cause of acute gastroenteritis in children worldwide. However, few prospective studies have analyzed astrovirus in community-dwelling pediatric populations in low-and-middle-income countries. Methods: We assessed the incidence, risk factors, clinical characteristics, genotypes, viral coinfections and seasonality of astrovirus gastroenteritis in 443 healthy Nicaraguan children born in 2017-2018, followed for 36 months. Children were recruited from maternity hospitals and birth records in an economically-diverse neighborhood of León, the second-largest city in Nicaragua. Astrovirus-positive episodes and genotypes were identified from diarrheal specimens with reverse transcription quantitative polymerase chain reaction and Sanger sequencing. Results: Of 1708 total specimens tested, eighty children (18%) experienced at least 1 astrovirus episode, and 9 experienced repeat episodes, mostly during the rainy season (May-October). The incidence of astrovirus episodes was 7.8/100 child-years (95% CI: 6.2, 9.8). Genotype-specific incidence of astrovirus also exhibited seasonality. Median age of astrovirus episode onset was 16 months (IQR 9, 23). Initial astrovirus episodes were not associated with protection against future episodes during the age span studied. Astrovirus cases were exclusively breastfed for a shorter period than uninfected children, and the human milk oligosaccharide lacto-N-fucopentaose-I was more concentrated in mothers of these children. Home toilets appeared to protect against future astrovirus episodes (HR=0.19, 95% CI 0.04-0.91). Human astrovirus-5 episodes, comprising 15% of all typed episodes, were associated with longer diarrhea and more symptomatic rotavirus co-infections. Conclusion: Astrovirus was a common cause of gastroenteritis in this cohort, and future studies should clarify the role of astrovirus genotype in clinical infection severity.

Infant antibody and B-cell responses following confirmed pediatric GII.17 norovirus infections functionally distinguish GII.17 genetic clusters.

Genogroup II (GII) noroviruses are a major cause of diarrheal disease burden in children in both high- and low-income countries. GII.17 noroviruses are composed of distinct genetic clusters (I, II, IIIa, and IIIb) and have shown potential for replacing historically more prevalent GII.4 strains, but the serological basis for GII.17 antigenic diversity has not been studied in children. Utilizing samples from a birth cohort, we investigated antibody and B-cell responses to GII.17 cluster variants in confirmed GII.17 infections in young children as well as demonstrated that the distinct genetic clusters co-circulate. Polyclonal serum antibodies bound multiple clusters but showed cluster-specific blockade activity in a surrogate virus neutralization assay. Antibodies secreted by immortalized memory B cells (MBCs) from an infant GII.17 case were highly specific to GII.17 and exhibited blockade activity against this genotype. We isolated an MBC-derived GII.17-specific Immunoglobulin A (IgA) monoclonal antibody called NVA.1 that potently and selectively blocked GII.17 cluster IIIb and recognized an epitope targeted in serum from cluster IIIb-infected children. These data indicate that multiple antigenically distinct GII.17 variants co-circulate in young children, suggesting retention of cluster diversity alongside potential for immune escape given the existence of antibody-defined cluster-specific epitopes elicited during infection.

Nonsecretor Phenotype Is Associated With Less Risk of Rotavirus-Associated Acute Gastroenteritis in a Vaccinated Nicaraguan Birth Cohort.

BACKGROUND: Histo-blood group antigens (HBGAs) have been associated with rotavirus vaccine take; but the effect of these HBGAs on rotavirus incidence and risk remains poorly explored in vaccinated populations. METHODS: Rotavirus-associated acute gastroenteritis (AGE) was assessed in 444 Nicaraguan children followed from birth until 3 years of age. AGE episodes were tested for rotavirus by reverse-transcription quantitative polymerase chain reaction, and saliva or blood was used to determine HBGA phenotypes. Cox proportional hazards models were used to estimate the relative hazard of rotavirus AGE by HBGA phenotypes. RESULTS: Rotavirus was detected in 109 (7%) stool samples from 1689 AGE episodes over 36 months of observation between June 2017 and July 2021. Forty-six samples were successfully genotyped. Of these, 15 (35%) were rotavirus vaccine strain G1P[8], followed by G8P[8] or G8P[nt] (11 [24%]) and equine-like G3P[8] (11 [24%]). The overall incidence of rotavirus-associated AGE was 9.2 per 100 child-years, and was significantly higher in secretor than nonsecretor children (9.8 vs 3.5/100 child-years, P = .002). CONCLUSIONS: The nonsecretor phenotype was associated with decreased risk of clinical rotavirus vaccine failure in a vaccinated Nicaraguan birth cohort. These results show the importance of secretor status on rotavirus risk, even in vaccinated children.

Neural tube defects: Prevalence, mortality, and maternal characteristics in two departmental hospitals in the northwestern region of Nicaragua, 2006-2018.

BACKGROUND: Congenital anomalies are the fifth most common cause of neonatal mortality in Nicaragua, and neural tube defects (NTDs) are the most common of all cases of lethality associated with a birth defect. Prevalence and mortality estimates are needed to propose effective intervention strategies that prevent NTDs over time. METHODS: A cross-sectional study was carried out in northwestern Nicaragua from January 2006 to December 2018. All cases of NTDs (anencephaly, spina bifida, and encephalocele) were registered in hospital surveillance systems, and the medical histories of the mothers and newborns were reviewed. Prevalence was calculated by considering the number of live births and stillbirths older than 20 weeks of gestation with NTDs, divided by the total number of live births and stillbirths in each study year. Neonatal mortality rate (NMR) for NTD, and case fatality for spina bifida was calculated. RESULTS: Two hundred fifty cases of NTDs were identified from 178,498 deliveries (177,316 live births and 1,182 stillbirths). The prevalence of NTDs during this time period was 14.01 (95% CI: 12.27-15.74) per 10,000 births. The prevalence of spina bifida (n = 140), anencephaly (n = 97), and encephalocele (n = 13) was 7.84, (95% CI: 6.54-9.14), 5.43 (95% CI: 4.30-6.45), and 0.73 (95% CI: 0.33-1.12) per 10,000 births, respectively. Mothers with fetus or newborns affected with NTDs did not use folic acid prior to conception, and 11% experienced periods of hyperthermia during the first trimester of pregnancy. NMR for NTDs was 0.55 per 1.000 livebirths. Case fatality for all NTDs and for spina bifida were 55% and 18%, respectively. CONCLUSION: The prevalence and mortality of NTDs in the northwestern region of Nicaragua present peaks and troughs during the study period. Spina bifida was the most frequent type of NTD. We believe that these findings could be of use by health policy makers to strengthen the primary prevention of NTDs in the region through the monitoring of the food fortification policy and folic acid supplementation to women of childbearing age. Additional etiologic studies of NTDs should be considered to identify additional prevention measures.

Household Surveillance for Norovirus Gastroenteritis in a Nicaraguan Birth Cohort: A Nested Case-Control Analysis of Norovirus Risk Factors.

Norovirus causes a large proportion of pediatric acute gastroenteritis (AGE) worldwide, and no vaccines are currently available. To inform public health measures against norovirus gastroenteritis, we assessed risk factors in a case-control study nested in a birth cohort study in Nicaragua. Between June 2017 and January 2022, we followed children weekly for AGE episodes, and collected stool specimens from symptomatic children. Risk factors for AGE were collected during routine weekly visits. Norovirus was detected in stools using real-time reverse transcriptase polymerase chain reaction and positive specimens were genotyped using Sanger sequencing. We included 40 norovirus-positive AGE children matched 1:2 to controls and conducted bivariate and multivariable analyses of norovirus AGE risk factors. Among typeable norovirus infections, GII.4 were more severe than non-GII.4 (four/twenty-one vs. one/nine) and accounted for all emergency visits and hospitalizations. Adjusted conditional logistic regression found that female sex and higher length-for-age Z score were protective against norovirus AGE; a dirt floor in the home, sharing cups or bottles, and recent contact with someone with AGE symptoms were associated with norovirus AGE, though estimates were highly imprecise. Reducing contact with symptomatic persons and with saliva or other bodily fluids on cups or floors could reduce infant norovirus incidence.

Timing and genotype distribution of symptomatic and asymptomatic sapovirus infections and re-infections in a Nicaraguan birth cohort.

OBJECTIVES: To characterize the timing and genotype distribution of symptomatic and asymptomatic sapovirus infections and re-infections in a Nicaraguan birth cohort. METHODS: Infants (N = 444) were enrolled at 10-14 days of life and observed weekly until 2 years of age. Stool samples were collected for each acute gastroenteritis (AGE) episode, and routine stool samples were collected monthly. Stool samples were tested for sapovirus using RT-qPCR, and positive samples were genotyped. RESULTS: A total of 348 children completed 2 years of AGE weekly surveillance; 93 (26.7%) of them experienced sapovirus AGE. Most infections occurred after 5 months of age and mainly during the second year of life (62.4%, 58/93) and early in the rainy season. Sapovirus screening in all stools from a subset of 67 children who consistently provided samples showed sapovirus infections in 91 of 330 (27.6%) AGE episodes and in 39 of 1350 (2.9%) routine stools. In this subset, the median age at the first sapovirus AGE was 11.2 months (95% CI, 9.3-15.9 months); 38 of 67 (57%) children experienced re-infections, 19 symptomatic and 19 asymptomatic. On average, sapovirus re-infections were reported 7.2 months after symptomatic and 5.3 months after asymptomatic infections. Genogroup GI (64%, 69/108) was the most common detected. Sapovirus GI.1 was more frequently detected in AGE stool samples than in routine stool samples (47.2%, 43/91 vs. 25.6%, 10/39; p 0.005), and re-infection with the same genotype was uncommon. DISCUSSION: The first sapovirus infections occurred at approximately 11 months of age, whereas the median time to symptomatic re-infection was 7.2 months. Re-infections with the same sapovirus genotype were rare during 2 years of life suggesting genotype-specific protection after natural infection.

Association between breastfeeding, host genetic factors, and calicivirus gastroenteritis in a Nicaraguan birth cohort.

BACKGROUND: Norovirus and sapovirus are important causes of childhood acute gastroenteritis (AGE). Breastfeeding prevents AGE generally; however, it is unknown if breastfeeding prevents AGE caused specifically by norovirus and sapovirus. METHODS: We investigated the association between breastfeeding and norovirus or sapovirus AGE episodes in a birth cohort. Weekly data on breastfeeding and AGE episodes were captured during the first year of life. Stools were collected from children with AGE and tested by RT-qPCR for norovirus and sapovirus. Time-dependent Cox models estimated associations between weekly breastfeeding and time to first norovirus or sapovirus AGE. FINDINGS: From June 2017 to July 2018, 444 newborns were enrolled in the study. In the first year of life, 69 and 34 children experienced a norovirus and a sapovirus episode, respectively. Exclusive breastfeeding lasted a median of 2 weeks, and any breastfeeding lasted a median of 43 weeks. Breastfeeding in the last week did not prevent norovirus (HR: 1.09, 95% CI: 0.62, 1.92) or sapovirus (HR: 1.00, 95% CI: 0.82, 1.21) AGE in a given week, adjusting for household sanitation, consumption of high-risk foods, and mother's and child's histo-blood group phenotypes. Maternal secretor-positive phenotype was protective against norovirus AGE, whereas child's secretor-positive phenotype was a risk factor for norovirus AGE. INTERPRETATION: Exclusive breastfeeding in this population was short-lived, and no conclusions could be drawn about its potential to prevent norovirus or sapovirus AGE. Non-exclusive breastfeeding did not prevent norovirus or sapovirus AGE in the first year of life. However, maternal secretor-positive phenotype was associated with a reduced hazard of norovirus AGE.

Norovirus Infection in Young Nicaraguan Children Induces Durable and Genotype-Specific Antibody Immunity.

There are significant challenges to the development of a pediatric norovirus vaccine, mainly due to the antigenic diversity among strains infecting young children. Characterizing human norovirus serotypes and understanding norovirus immunity in naïve children would provide key information for designing rational vaccine platforms. In this study, 26 Nicaraguan children experiencing their first norovirus acute gastroenteritis (AGE) episode during the first 18 months of life were investigated. We used a surrogate neutralization assay that measured antibodies blocking the binding of 13 different norovirus virus-like particles (VLPs) to histo-blood group antigens (HBGAs) in pre- and post-infection sera. To assess for asymptomatic norovirus infections, stools from asymptomatic children were collected monthly, screened for norovirus by RT-qPCR and genotyped by sequencing. Seroconversion of an HBGA-blocking antibody matched the infecting genotype in 25 (96%) of the 26 children. A subset of 13 (50%) and 4 (15%) of the 26 children experienced monotypic GII and GI seroconversion, respectively, strongly suggesting a type-specific response in naïve children, and 9 (35%) showed multitypic seroconversion. The most frequent pairing in multitypic seroconversion (8/12) were GII.4 Sydney and GII.12 noroviruses, both co-circulating at the time. Blocking antibody titers to these two genotypes did not correlate with each other, suggesting multiple exposure rather than cross-reactivity between genotypes. In addition, GII titers remained consistent for at least 19 months post-infection, demonstrating durable immunity. In conclusion, the first natural norovirus gastroenteritis episodes in these young children were dominated by a limited number of genotypes and induced responses of antibodies blocking binding of norovirus VLPs in a genotype-specific manner, suggesting that an effective pediatric norovirus vaccine likely needs to be multivalent and include globally dominant genotypes. The duration of protection from natural infections provides optimism for pediatric norovirus vaccines administered early in life.

Preexisting Heterotypic Ligand-blocking Antibody Does Not Protect Against Genogroup II Norovirus Episodes in Young Children.

A birth cohort design was used to understand whether heterotypic ligand-blocking norovirus antibodies provide cross-protection within the GII genogroup. We found that almost one-half of children who experienced a norovirus GII episode had preexisting antibodies heterotypic to the infecting genotype; therefore, these antibodies did not provide cross-protection.

First Episodes of Norovirus and Sapovirus Gastroenteritis Protect Against Subsequent Episodes in a Nicaraguan Birth Cohort.

BACKGROUND: Norovirus and sapovirus cause a large burden of acute gastroenteritis (AGE) in young children. We assessed protection conferred by norovirus and sapovirus AGE episodes against future episodes. METHODS: Between June 2017 and July 2018, we recruited 444 newborns in León, Nicaragua. Weekly household surveys identified AGE episodes over 36 months, and AGE stools were tested by reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) for norovirus genogroup (G)I/GII and sapovirus. We used recurrent-event Cox models and negative control methods to estimate protection conferred by first episodes, controlling for observed and unobserved risk factors, respectively. RESULTS: Sapovirus episodes conferred a 69% reduced hazard of subsequent episodes using the negative control method. Norovirus GI (hazard ratio [HR] = 0.67; 95% confidence interval [CI] = 0.31, 1.3) and GII (HR = 0.20; 95% CI = 0.04, 0.44) episodes also appeared highly protective. Protection against norovirus GII was enhanced following two episodes. CONCLUSIONS: Evidence of natural immunity in early childhood provides optimism for the future success of pediatric norovirus and sapovirus vaccines.

Secretor Status Strongly Influences the Incidence of Symptomatic Norovirus Infection in a Genotype-Dependent Manner in a Nicaraguan Birth Cohort.

BACKGROUND: The role of histo-blood group on the burden and severity of norovirus gastroenteritis in young infants has not been well documented. METHODS: Norovirus gastroenteritis was assessed in 443 Nicaraguan children followed from birth until 3 years of age. Stool samples were tested for norovirus by reverse-transcription quantitative polymerase chain reaction (RT-qPCR), and histo-blood group antigens (HBGAs) were determined by phenotyping of saliva and blood. Hazard ratios and predictors of norovirus acute gastroenteritis (AGE) outcome stratified by HBGA were estimated using Cox proportional hazards models. RESULTS: Of 1353 AGE episodes experienced by children, 229 (17%) tested positive for norovirus with an overall incidence of 21.9/100 child-years. Secretor children were infected as early as 2 months of age and had a higher incidence of norovirus GII compared to nonsecretor children (15.4 vs 4.1/100 child-years, P = .006). Furthermore, all GII.4 AGE episodes occurred in secretor children. Children infected with GI (adjusted odds ratio [aOR], 0.09 [95% confidence interval {CI}, .02-.33]) or non-GII.4 viruses (aOR, 0.2 [95% CI, .07-.6]) were less likely to have severe AGE compared to GII.4-infected children. CONCLUSIONS: Secretor status in children strongly influences the incidence of symptomatic norovirus infection in a genogroup or genotype-dependent manner and provides evidence that clinical severity in children depends on norovirus genotypes.

Serological Humoral Immunity Following Natural Infection of Children with High Burden Gastrointestinal Viruses.

Acute gastroenteritis (AGE) is a major cause of morbidity and mortality worldwide, resulting in an estimated 440,571 deaths of children under age 5 annually. Rotavirus, norovirus, and sapovirus are leading causes of childhood AGE. A successful rotavirus vaccine has reduced rotavirus hospitalizations by more than 50%. Using rotavirus as a guide, elucidating the determinants, breath, and duration of serological antibody immunity to AGE viruses, as well as host genetic factors that define susceptibility is essential for informing development of future vaccines and improving current vaccine candidates. Here, we summarize the current knowledge of disease burden and serological antibody immunity following natural infection to inform further vaccine development for these three high-burden viruses.

Antibody response to SARS-CoV-2 infection over six months among Nicaraguan outpatients.

New information is emerging about SARS-CoV-2 epidemiology and immunity, but little of this information comes from low- and middle-income countries or from patients receiving care in the outpatient setting. The current study investigated the SARS-CoV-2 infection status and antibody responses in 157 patients seeking care for a respiratory disease suggestive of COVID-19 in private healthcare clinics during the first wave (June-October 2020) of infections in Nicaragua. We examined nasal swabs for the presence of viral RNA via RT-PCR and longitudinally collected sera for the changes in SARS-CoV-2 Spike antibody levels over six months. Among patients with confirmed SARS-CoV-2 infections, we evaluated if clinical symptoms were associated with age, hematological parameters and co-morbidities. The combination of PCR and paired serology identified 60 (38%) of the 157 outpatients as acute COVID-19. While both PCR and serology identified the majority (n = 38, 64%) of the acute infections, a notable number of outpatients were identified by RT-qPCR (n = 13, 22%) or by serology (n = 9, 14%) only. During the longitudinal study, we identified 6 new infections by serology among the 97 non-COVID-19 subjects. In conclusion, this study report that more than one third of the outpatients seeking care for acute respiratory disease during the first epidemic wave of SARS-CoV-2 in Nicaragua had an acute mild COVID-19 infection that correlate with prolonged humoral response. This immune response to the RBD antigen, more likely IgG dependent, significantly increased between the acute to convalescent and decay in the late convalescent but still remained seropositive.

Seroepidemiology of SARS-CoV-2 infections in an urban Nicaraguan population.

In a Nicaraguan population-based cohort, SARS-CoV-2 seroprevalence was 34%, with higher prevalence in children compared to adults. Having a seropositive household member was associated with a two-fold probability of individual seropositivity, suggesting a role for household transmission. Co-morbidities and preventive behaviors were not associated with SARS-CoV-2 seroprevalence.

Clinical Characteristics, Risk Factors, and Population Attributable Fraction for Campylobacteriosis in a Nicaraguan Birth Cohort.

Campylobacteriosis is an important contributor to the global burden of acute gastroenteritis (AGE). In Nicaragua, the burden, risk factors, and species diversity for infant campylobacteriosis are unknown. Between June 2017 and December 2018, we enrolled 444 infants from León, Nicaragua, in a population-based birth cohort, conducting weekly household AGE surveillance. First, we described clinical characteristics of symptomatic Campylobacter infections, and then compared clinical characteristics between Campylobacter jejuni/coli and non-jejuni/coli infections. Next, we conducted a nested case-control analysis to examine campylobacteriosis risk factors. Finally, we estimated the population attributable fraction of campylobacteriosis among infants experiencing AGE. Of 296 AGE episodes in the first year of life, Campylobacter was detected in 59 (20%), 39 were C. jejuni/coli, and 20 were non-jejuni/coli species, including the first report of Campylobacter vulpis infection in humans. Acute gastroenteritis symptoms associated with C. jejuni/coli lasted longer than those attributed to other Campylobacter species. In a conditional logistic regression model, chickens in the home (odds ratio [OR]: 3.8, 95% CI: 1.4-9.8), a prior AGE episode (OR: 3.3; 95% CI: 1.4-7.8), and poverty (OR: 0.4; 95% CI: 0.2-0.9) were independently associated with campylobacteriosis. Comparing 90 infants experiencing AGE with 90 healthy controls, 22.4% (95% CI: 11.2-32.1) of AGE episodes in the first year of life could be attributed to Campylobacter infection. Campylobacter infections contribute substantially to infant AGE in León, Nicaragua, with non-jejuni/coli species frequently detected. Reducing contact with poultry in the home and interventions to prevent all-cause AGE may reduce campylobacteriosis in this setting.

Association of Genetic Polymorphisms in DC-SIGN, Toll-Like Receptor 3, and Tumor Necrosis Factor α Genes and the Lewis-Negative Phenotype With Chikungunya Infection and Disease in Nicaragua.

BACKGROUND: Chikungunya infections range from subclinical infection to debilitating arthralgia and to chronic inflammatory rheumatism. Tumor necrosis factor (TNF) α, DC-SIGN (dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin), Toll-like receptor (TLR) 3, and blood groups have been directly or indirectly implicated in the susceptibility and pathogenesis of chikungunya. METHODS: To test the hypothesis that polymorphisms in genes coding for these molecules determine clinical outcomes of chikungunya infection, a retrospective case-control study was performed in León, Nicaragua. The study included 132 case patients and 132 controls, matched for age, sex and neighborhood. Case patients had clinical symptoms of chikungunya, which was diagnosed by means of polymerase chain reaction. Controls were individuals not reporting abrupt presentation of clinical chikungunya-like symptoms. Polymorphisms were identified by TaqMan single-nucleotide polymorphism genotyping assays. RESULTS: After adjustment for sociodemographic risk factors, chikungunya disease was associated with polymorphism in DC-SIGN and TLR3 genes (odds ratios, 5.2 and 3.3, respectively), and TNF-α with reduced persistent joint pain (0.24). Persistent joint pain was also associated with age, female sex and other comorbid conditions. Most interestingly, the Lewis-negative phenotype was strongly associated with both symptomatic chikungunya and immunoglobulin G seropositivity (odds ratios, 2.7, and 3.3, respectively). CONCLUSION: This study identified polymorphisms in DC-SIGN, TLR3, and TNF-α genes as well as Lewis-negative phenotype as risk factors for chikungunya infection and disease progression.

Risk Factors and Clinical Profile of Sapovirus-associated Acute Gastroenteritis in Early Childhood: A Nicaraguan Birth Cohort Study.

BACKGROUND: Sapovirus is increasingly recognized as an important cause of acute gastroenteritis (AGE) in children. We identified risk factors and characterized the clinical profile of sapovirus AGE in a birth cohort in León, Nicaragua. METHODS: We conducted a case-control study nested within a birth cohort (n = 444). Fieldworkers conducted weekly household AGE surveillance. AGE stools were tested for sapovirus by reverse transcriptase quantitative polymerase chain reaction. For each first sapovirus episode, we selected 2 healthy age-matched controls and estimated independent risk factors of sapovirus AGE using conditional logistic regression. We compared clinical characteristics of sapovirus AGE episodes with episodes associated with other etiologies and identified co-infections with other enteric pathogens. RESULTS: From June 2017 to July 2019, we identified 63 first sapovirus AGE episodes and selected 126 controls. Having contact with an individual with AGE symptoms and vaginal delivery were independent risk factors for sapovirus AGE. All cases experienced diarrhea, lasting a median 6 days; 23% experienced vomiting. Compared with children with AGE due to another etiology, sapovirus AGE was similar in severity, with less reported fever. Most cases experienced co-infections and were more likely than controls to be infected with diarrheagenic Escherichia coli or astrovirus. CONCLUSIONS: Sapovirus was a commonly identified AGE etiology in this Central American setting, and symptoms were similar to AGE associated with other etiologies. The association between vaginal delivery and sapovirus is a novel finding. Gut microbiome composition might mediate this relationship, or vaginal delivery might be a proxy for other risk factors. Further investigation into more specific biological mechanisms is warranted.

Zika RNA and Flavivirus-Like Antigens in the Sperm Cells of Symptomatic and Asymptomatic Subjects.

Zika virus (ZIKV) RNA has been found to remain in human semen for up to one year after infection, but the presence of Flavivirus antigens in the different compartments of semen has been largely unexplored. Following the introduction of ZIKV in Nicaragua (2016), a prospective study of patients with clinical symptoms consistent with ZIKV was conducted in León to investigate virus shedding in different fluids. ZIKV infection was confirmed in 16 male subjects (≥18 years of age) by RT-qPCR in either blood, saliva or urine. Of these, three provided semen samples at 7, 14, 21, 28, 60 and 180 days postsymptom onset (DPSO) for Flavivirus antigens and RNA studies. These cases were compared with 19 asymptomatic controls. Flavivirus antigens were examined by immunofluorescence (IF) using the 4G2 Mabs, and confocal microscopy was used to explore fluorescence patterns. The three (100%) symptomatic subjects and 3 (16%) of the 19 asymptomatic subjects had Flavivirus antigens and viral RNA in the spermatozoa fraction. The percentage of IF Flavivirus-positive spermatozoa cells ranged from 1.9% to 25% in specimens from symptomatic subjects, as compared with 0.8% to 3.8% in specimens from asymptomatic controls. A marked IF-pattern in the cytoplasmic droplets and tail of the spermatozoa was observed. The sperm concentrations (45 × 106/mL vs. 63.5 × 106/mL, p = 0.041) and the total motility percentage (54% vs. 75%, p = 0.009) were significantly lower in specimens from ZIKV-positive than in those of ZIKV-negative. In conclusion, this study demonstrated the presence of Flavivirus antigens and RNA within a time frame of 28 DPSO in sperm cells of symptomatic and asymptomatic subjects during the ZIKV epidemic. These findings have implications for public health, in terms of nonarthropod-born, silent transmission facilitated by sperm cells and potential transmission from asymptomatic males to pregnant women, with consequences to the fetus.

Seroepidemiology of SARS-CoV-2 infections in an urban population-based cohort in León, Nicaragua.

In a Nicaraguan population-based cohort, SARS-CoV-2 seroprevalence reached 28% in the first 6 months of the country's epidemic and reached 35% 6 months later. Immune waning was uncommon. Individuals with a seropositive household member were over three times as likely to be seropositive themselves, suggesting the importance of household transmission.