BackgroundThe implementation of vector control interventions and potential introduction new tools requires baseline data to evaluate their direct and indirect effects. The objective of the study is to present the seroprevalence of dengue infection in a cohort of children 0 to 15 years old followed during 2015 to 2016, the risk factors and the role of enhanced surveillance strategies in three urban sites (Merida, Ticul and Progreso) in Yucatan, Mexico.MethodsA cohort of school children and their family members was randomly selected in three urban areas with different demographic, social conditions and levels of transmission. We included results from 1,844 children aged 0 to 15 years. Serum samples were tested for IgG, NS1 and IgM. Enhanced surveillance strategies were established in schools (absenteeism) and cohort families (toll-free number).ResultsSeroprevalence in children 0 to 15 years old was 46.8 (CI 95% 44.1–49.6) with no difference by sex except in Ticul. Prevalence increased with age and was significantly lower in 0 to 5 years old (26.9%, 95% CI:18.4–35.4) compared with 6 to 8 years old (43.9%, 95% CI:40.1–47.7) and 9 to 15 years old (61.4%, 95% CI:58.0–64.8). Sharing the domestic space with other families increased the risk 1.7 times over the individual families that own or rented their house, while risk was significantly higher when kitchen and bathroom were outside. Complete protection with screens in doors and windows decreased risk of infection. Seroprevalence was significantly higher in the medium and high risk areas.ConclusionsThe prevalence of antibodies in children 0 to 15 years in three urban settings in the state of Yucatan describe the high exposure and the heterogenous transmission of dengue virus by risk areas and between schools in the study sites. The enhanced surveillance strategy was useful to improve detection of dengue cases with the coincident transmission of chikungunya and Zika viruses.

Composition of urinary stones in children from Yucatán, México, is calcium and uric acid. Polymorphisms in VDR and ZNF365 genes have been associated to calcium and uric acid lithiasis, respectively. We evaluated the association of polymorphisms TaqI and FokI of VDR gene and Ala62Thr of ZNF365 gene with the metabolic disorders (MD) in children with urolithiasis (UL). We included 109 children with UL. Creatinine, calcium, phosphorus, magnesium, uric acid, oxalates and citrates were measured in fresh urine. Urinary indices were calculated for determining the MD. VDR and ZNF365 polymorphisms were determined by PCR-RFLP. Genotype frequencies were compared with the frequency of MD and with the averages of excretion of the analytes, using the statistical package STATA 11.0. The most frequent MD were hypocitraturia (35.8 %) and hyperuricosuria (22.9 %). The comparison of genotype frequencies with the frequency of MD did not show significant differences (p > 0.05). The comparison of the urinary excretion averages of analytes with respect to the genotype showed that GG homozygotes have higher concentrations of uric acid and citrate than AG heterozygotes (p = 0.03), and that fF heterozygotes have lower concentrations of citrate (p = 0.009). Hypocitraturia and hyperuricosuria were the most common metabolic disorders. The frequency of MD is not associated with polymorphisms. However, in children with urolithiasis of Yucatan, GG homozygotes excrete higher concentrations of uric acid and citrates, and fF heterozygotes have lower concentrations of citrates.

The 2012 and 2013 annual influenza epidemics in Mexico were characterized by presenting different seasonal patterns. In 2012 the A(H1N1)pdm09 virus caused a high incidence of influenza infections after a two-year period of low circulation; whereas the 2013 epidemic presented circulation of the A(H1N1)pdm09 virus throughout the year. We have characterized the molecular composition of the Hemagglutinin (HA) and Neuraminidase (NA) genes of the A(H1N1)pdm09 virus from both epidemic seasons, emphasizing the genetic characteristics of viruses isolated from Yucatan in Southern Mexico. The molecular analysis of viruses from the 2012 revealed that all viruses from Mexico were predominantly grouped in clade 7. Strikingly, the molecular characterization of viruses from 2013 revealed that viruses circulating in Yucatan were genetically different to viruses from other regions of Mexico. In fact, we identified the occurrence of two genetic variants containing relevant mutations at both the HA and NA surface antigens. There was a difference on the temporal circulation of each genetic variant, viruses containing the mutations HA-A141T / NA-N341S were detected in May, June and July; whereas viruses containing the mutations HA-S162I / NA-L206S circulated in August and September. We discuss the significance of these novel genetic changes.

Urolithiasis (UL) is an endemic disease in Southeastern, Mexico. In order to evaluate the association of I550V polymorphism in the hNaDC-1 gene with risk for hypocitraturia and/or for UL; 139 adults with UL and 132 adults without UL, were included under a case-control association study. Citrate levels in 24-h urine were quantified (citraturia). The polymorphism I550V-hNaDC-1 was determined by PCR-RFLP. Statistical analysis was performed using the STATA10.2 software. Comparison of genotype and allele frequencies between subjects with and without UL showed significant differences for genotype bb (OR = 2.34, CI: 1.19 -4.59, p = 0.01) and for allele b (OR = 1.62, CI: 1.15 -2.28, p = 0.005), suggesting an association with the risk for UL. Comparison of genotype and allele frequencies between subjects with hypocitraturia and subjects with normocitraturia, did not show any significant difference (p > 0.05), suggesting that this polymorphism is not associated with the risk of hypocitraturia. Interestingly, the risk for UL was increased due to an additive effect of hypocitraturia with the genotype bb (OR = 6.6, CI: 2.38 -18.28, p = 0.0002) or with the allele b (OR: 4.2, CI = 2.52 -6.97, p < 0.0001) in the studied population.

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