TASK DEFINITION: In this task, you are given a passage which has a question and the context. You have to generate an answer to the question based on the information present in the context.
PROBLEM: Context: Aedes aegypti is the main mosquito vector of the four serotypes of dengue virus (DENV). Previous population genetic and vector competence studies have demonstrated substantial genetic structure and major differences in the ability to transmit dengue viruses in Ae. aegypti populations in Mexico.', 'Population genetic studies revealed that the intersection of the Neovolcanic axis (NVA) with the Gulf of Mexico coast in the state of Veracruz acts as a discrete barrier to gene flow among Ae. aegypti populations north and south of the NVA. The mosquito populations north and south of the NVA also differed in their vector competence (VC) for dengue serotype 2 virus (DENV2). The average VC rate for Ae. aegypti mosquitoes from populations from north of the NVA was 0.55; in contrast the average VC rate for mosquitoes from populations from south of the NVA was 0.20. Most of this variation was attributable to a midgut infection and escape barriers. In Ae. aegypti north of the NVA 21.5% failed to develop midgut infections and 30.3% of those with an infected midgut failed to develop a disseminated infection. In contrast, south of the NVA 45.2% failed to develop midgut infections and 62.8% of those with an infected midgut failed to develop a disseminated infection.\Question: Is the neovolcanic axis a barrier to gene flow among Aedes aegypti populations in Mexico that differ in vector competence for Dengue 2 virus?

SOLUTION: Barriers to gene flow in vector populations may also impact the frequency of genes that condition continuous and epidemiologically relevant traits such as vector competence. Further studies are warranted to determine why the NVA is a barrier to gene flow and to determine whether the differences in vector competence seen north and south of the NVA are stable and epidemiologically significant.

PROBLEM: Context: The incidence and predictors of spontaneous hepatitis B surface-antigen (HBsAg) seroclearance in patients with chronic hepatitis B virus (HBV) were evaluated.', 'A total of 1427 patients with chronic HBV infection, who were followed between 1994 and 2013, were investigated in this retrospective study. All data were extracted from patient files.', 'Spontaneous HBsAg seroclearance occurred in 84 patients during 8798 person-years of follow-up. The patients were categorized into 3 groups at follow-up based on HBV DNA features as continuously <100 copies/mL (Group A), 0-10,000 copies/mL (Group B), and 0 to >10,000 copies/mL (Group C). Alanine aminotransferase features in the 2 groups were categorized as continuously normal (<40 U/L) and 0 to >40 U/L. Spontaneous HBsAg seroclearance was seen primarily in patients with Group A HBV DNA features, and continuously low HBV DNA values were the main predictor of HBsAg seroclearance (P < 0.001).\Question: Is a persistently low HBV DNA level a predictor of spontaneous HBsAg clearance in patients with chronic hepatitis B?

SOLUTION: These results suggest that a continuously low viral load is the most important factor affecting spontaneous HBsAg seroclearance.

PROBLEM: Context: To establish the determinants of weight, length and head circumference changes during their initial hospitalization in very-low-birth-weight preterm infants.', "A prospective cohort study was performed. Weight z-score and percentage of target dietary intakes (TDIs) were prospectively determined daily during the first 5 weeks of life in a group of preterm infants (n = 111, birth weight <1,500 g, gestational age <34 weeks). Weight, length and head circumference at 36 weeks' postmenstrual age (PMA) were recorded. A mixed effects regression model was used to evaluate changes in weight z-score during the first 5 weeks of life. Simple Pearson correlations and stepwise logistic regression were used to determine the relationship between fetal growth, illness severity, nutritional intake and growth at 36 weeks' PMA.", "Weight z-score decreased significantly in all infants during the first 5 weeks of life from -0.92 ± 0.66 at birth to -1.89 ± 0.65 at 5 weeks. The variation of weight z-score during the first 5 weeks of life was influenced by weight z-score at birth, energy and protein intakes and gestational age. Mean energy and protein intakes were 95.5 and 86.4% of TDIs. Weight z-score fell to -2.05 ± 0.64 at 36 weeks' PMA. Birth weight z-score was significantly correlated with weight z-score at 36 weeks (R2 = 0.71; p < 0.001). Severity of illness influenced the weight z-score at 36 weeks.\Question: Is growth in preterm infants until 36 weeks ' postmenstrual age close to target recommendations?

SOLUTION:
Despite achieving a protein and energy intake close to the described target intake, the rate of growth in our infants was lower than indicated by the intrauterine growth curve. Lower gestational age, lower birth weight and severe illness had a negative effect on growth.