Seroepidemiological Studies of Arboviruses in Africa.

The literature on sero-epidemiological studies of flaviviral infections in the African continent is quite scarce. Much of the viral epidemiology studies have been focussing on diseases such as HIV/AIDS because of their sheer magnitude and impact on the lives of people in the various affected countries. Increasingly disease outbreaks caused by arboviruses such as the recent cases of chikungunya virus, dengue virus and yellow fever virus have prompted renewed interest in studying these viruses. International agencies from the US, several EU nations and China are starting to build collaborations to build capacity in many African countries together with established institutions to conduct these studies. The Tofo Advanced Study Week (TASW) was established to bring the best scientists from the world to the tiny seaside town of Praia do Tofo to rub shoulders with African virologists and discuss cutting-edge science and listen to the work of researchers in the field. In 2015 the 1st TASW focussed on Ebola virus. The collections of abstracts from participants at the 2nd TASW which focused on Dengue and Zika virus as well as presentations on other arboviruses are collated in this chapter.

Examination of the folding of E. coli CspA through tryptophan substitutions.

Escherichia coli cold shock protein, CspA, folds very rapidly (time constant, tau = 4 msec) by an apparent two-state mechanism. However, recent time-resolved infrared (IR) temperature-jump experiments indicate that the folding trajectory of CspA may be more complicated. The sole tryptophan of wild-type CspA (Trp11), which is used to monitor the folding process by fluorescence spectroscopy, is located in an unusual aromatic cluster on the surface of CspA within the nucleic acid binding site. To gain a more global picture of the folding kinetics of CspA and to determine if there are any previously undetected intermediates, we have introduced a second tryptophan at three different surface locations in the protein. The three mutations did not significantly alter the tertiary structure of CspA, although two of the substitutions were found to be slightly stabilizing. Two-state folding, as detected by stopped-flow fluorescence spectroscopy, is preserved in all three mutants. These results indicate that the fast folding of CspA is driven by a concerted mechanism.

Role of a solvent-exposed aromatic cluster in the folding of Escherichia coli CspA.

Escherichia coli CspA is a member of the cold shock protein family. All cold shock proteins studied to date fold rapidly by an apparent two-state mechanism. CspA contains an unusual cluster of aromatic amino acids on its surface that is necessary for nucleic acid binding and also provides stability to CspA (Hillier et al., 1998). To elucidate the role this aromatic cluster plays in the determining the folding rate and pathway of CspA, we have studied the folding kinetics of mutants containing either leucine or serine substituted for Phe 18, Phe20, and/or Phe31. The leucine substitutions are found to accelerate folding and the serine substitutions to decelerate folding. Because these residues exert effects on the free energy of the folding transition state, they may be necessary for nucleating folding. They are not responsible, however, for the very compact, native-like transition state ensemble seen in the cold shock proteins, as the refolding rates of the mutants all show a similar, weak dependence of unfolding rate on denaturant concentration. Using mutant cycle analysis, we show that there is energetic coupling among the three residues between the unfolded and transition states, suggesting that the cooperative nature of these interactions helps to determine the unfolding rate. Overall, our results suggest that separate evolutionary pressures can act simultaneously on the same group of residues to maintain function, stability, and folding rate.

Body fatness and bioelectrical impedance in non-obese pre-menarcheal girls: comparison to anthropometry and evaluation of predictive equations.

OBJECTIVES: To determine in non-obese pre-menarcheal girls if bioelectrical impedance (BIA) is a better predictor of body fatness than triceps skinfold (TSF) or body mass index (BMI) and to cross-validate published equations for determination of fat-free mass (FFM) from BIA in pre-menarcheal girls. DESIGN: Cross-sectional analysis of data from 132 non-obese pre-menarcheal girls. The relationship of percent body fat (%BF), derived from isotopic dilution of H2 18O to TSF, BMI, and %BF by BIA, calculated from measures of height, weight and resistance was examined by correlation analysis. SETTING: Massachusetts Institute of Technology (MIT) Clinical Research Center in Cambridge, MA, USA. SUBJECTS: Pre-menarcheal girls aged 8-12 y were recruited from local schools, MIT summer day camp and by word of mouth. RESULTS: TSF accounted for 68% of the explained variance (R2) in the prediction of %BF measured by H2 18O, compared to 38% for BMI and 70% for BIA. Prediction of FFM by comparison of published equations was evaluated in this population. The predictive ability differed by Tanner stage. Kushner's equation (Kushner et al, 1992), based solely on height2/resistance was the only equation that provided estimates that did not differ significantly from measured values among all Tanner stages. CONCLUSIONS: BIA appears to be a valid and reliable measure of FFM but is no better than TSF in predictions of body fat.

Factors influencing infant mortality in Vietnam.

Selected determinants of overall infant mortality in Vietnam were examined using data from the 1988 Vietnam Demographic and Health Survey, and factors underlying neonatal and post-neonatal mortality were also compared. Effects of community development characteristics, including health care, were studied by logistic regression analysis in a subsample of rural children from the 1990 Vietnam Accessibility of Contraceptives Survey. Infant neonatal and post-neonatal mortality rates showed comparable distributions by birth order, maternal age, pregnancy intervals, mother's education and urban-rural residence. Rates were highest among first order births, births after an interval of less than 12 months, births to illiterate mothers and to those aged under 21 or over 35 years of age. Logistic regression analysis showed that the most significant predictor of infant mortality was residence in a province where overall infant mortality was over 40 per 1000 live births. In the rural subsample, availability of public transport was the most persistent community development predictor of infant mortality. Reasons for the low infant mortality rates in Vietnam compared to countries with similar levels of economic development are discussed.

PIP: The purposes of this study of infant mortality in Viet Nam were to determine the contribution of select variables to infant mortality and to compare these determinants with determinants of neonatal and postneonatal mortality. Data were obtained from the 1988 Vietnam Demographic and Health Survey (DHS) and the Vietnam Accessibility of Contraceptives Study in 1990. The DHS Sample included 4172 women aged 15-49 years and reports on 4884 children born between 1983 and 1988 and a subsample of 3382 children born in rural areas between 1983 and 1988. Explanatory variables were mother's age at time of birth, mother's education, birth order, sex, previous birth interval, the infant mortality risk status of the province, residence, and regional location. The accessibility survey provided data on availability of health care services, characteristics of the village, and geography of the area. Logistic regression showed that none of the explanatory variables significantly affected the infant mortality rate (IMR) for first births. For second and higher order births, provincial infant mortality risk was the only significant explanatory variable for IMR, and for postneonatal mortality for first births total, and for second and higher order births in the rural population. Risk was higher in areas with a higher than 40/1000 IMR. For second and higher order births, none of the explanatory variables was a significant predictor of neonatal, postneonatal, or infant mortality for all areas. Birth orders of 2-4 had a significantly lower risk of infant mortality than birth order of 5 or greater. In the rural subsample, high and low risk provinces were equally likely to live among the mountains and highlands; high risk provinces were more likely to be in coastal and delta areas. Children from intermediate sized villages were more likely to live in high risk provinces from those living in villages of under 2000 population or larger villages with 10,000 population. Lower infant mortality rates were associated with living in areas with public transport, a secondary school, a telephone, and electricity. Low risk infant mortality provinces also had higher proportions of children living 10 km from a polyclinic which was open over 24 hour/weeks and having a nurse or midwife available. More children with a village midwife lived in high risk provinces. The presence of public transport was associated with a significantly lower IMR.

Contraceptive use in Vietnam: the effect of individual and community characteristics.

Data from the 1988 Vietnamese Demographic and Health Survey and the 1990 Vietnam Study of Accessibility of Contraceptives were used in this analysis to determine how selective individual and community characteristics influenced the use of modern methods of contraception in Vietnam. Although there were no significant differences in the use of contraceptives between women with a primary education and those with a higher educational attainment, the illiterate women with no formal education were significantly less likely to use modern methods of contraception. Women living in provinces with high infant mortality rates were significantly less likely to use modern methods of contraception than women in low-infant-mortality provinces. Independent of other individual and community characteristics, there were no significant differences in the use of contraception between urban and rural women.

Fertility and family planning in Vietnam.

This report provides the first reliable statistical data on fertility patterns and the family planning program in the Socialist Republic of Vietnam. Findings are from the 1988 Demographic and Health Survey of Vietnam and the 1989 census survey. The data show that the total fertility rate has declined from over 6 children per woman in the early 1970s to under 4 in the later 1980s. Contraceptive prevalence for modern methods is estimated at 37 percent among married women of reproductive age in 1988. The average duration of breastfeeding is over 14 months; marriage is relatively late. The IUD is the most common contraceptive method and abortion is widespread. The major factors likely to influence fertility and family planning in the future are the government's population policy, improved access to modern methods of contraception, and the institution of new economic policies that are currently under way in Vietnam.

PIP: An analysis of data gathered in the 1988 Vietnam Demographic and health Survey (VNDHS) and the 1989 Census Population Five Percent Sample suggests that the country has been undergoing a process of demographic transition since the reunification of North and South Vietnam in 1975. The total fertility rate has declined from 6.1 in 1969-1974 to slightly under 4.0 in 1988-89. Factors apparently promoting this decline include changes in nuptiality patterns (in 1988, the mean age at marriage was 23.5 years and only 60% of women of reproductive age were married), a low infant mortality rate (50/1000 live births in 1988-89), growing acceptance of the government's 2-child family size norm (desired family size stands at 2.7 children among rural women and 2.3 children among urban women), and a well-organized national family planning program (54% of currently married Vietnamese women 15-44 years of age were contraceptive users in 1988). 63% of contraceptive acceptors use the IUD--the method promoted by the government's family planning effort--but there appear to be problems with the quality of IUDs provided. 45% of ever-users of clinic methods and 19% of users of supply methods utilize the commune health center and another 37% and 24%, respectively, are supplied through district hospitals. The ability of the national family planning program to offer a range of contraceptive choices has been hindered by a severe fiscal crisis in the health sector, and privatization and decentralization are receiving consideration as possible solutions. Local demographers are currently assessing whether further economic renovation is likely to support further demographic transitions or undermine policy enforcement by weakening the influence of rural cadres.