Publications

Epigenetic mechanisms provide an adaptive layer of control in the regulation of gene expression that enables an organism to adjust to a changing environment. Epigenetic regulation increases the functional complexity of deoxyribonucleic acid (DNA) by altering chromatin structure, nuclear organization, and transcript stability. These changes may additively or synergistically influence gene expression and result in long-term molecular and functional consequences independent of the DNA sequence that may ultimately define an individual's phenotype. This article (1) describes histone modification, DNA methylation, and expression of small noncoding RNA species; (2) reviews the most common methods used to measure these epigenetic changes; and (3) presents factors that need to be considered when choosing a specific tissue to evaluate for epigenetic changes.

The International Conference on Human Immunity to Tuberculosis, held in April 2012 in Atlanta, Georgia, USA provided the opportunity to discuss the current state of knowledge, important knowledge gaps, and approaches to overcoming obstacles to better understand protective and pathological immunity.

Vitamin D deficiency is a common condition that has well-documented effects on musculoskeletal health. A growing body of literature has related vitamin D deficiency to other chronic disorders, including cardiovascular disease. Several plausible biological mechanisms have been postulated to explain this association, including the effect of poor vitamin D status on intermediate risk factors (eg, hypertension and diabetes), neurohormonal activation, inflammation, and cardiac remodeling. These mechanisms have been explored in experimental and animal studies, as well as several small interventional studies. The results of the controlled trials have not been conclusive to date. In this review, we summarize the existing studies investigating the effects of vitamin D on cardiovascular health, and propose that additional well-designed, prospective, randomized controlled trials are necessary to delineate the appropriate role of vitamin D supplementation in reducing the burden of cardiovascular disease.

BACKGROUND

Typhoid and paratyphoid fever remain important causes of morbidity worldwide. Accurate disease burden estimates are needed to guide policy decisions and prevention and control strategies.

METHODS

We conducted a systematic literature review of the PubMed and Scopus databases using pre-defined criteria to identify population-based studies with typhoid fever incidence data published between 1980 and 2009. We also abstracted data from annual reports of notifiable diseases in countries with advanced surveillance systems. Typhoid and paratyphoid fever input data were grouped into regions and regional incidence and mortality rates were estimated. Incidence data were extrapolated across regions for those lacking data. Age-specific incidence rates were derived for regions where age-specific data were available. Crude and adjusted estimates of the global typhoid fever burden were calculated.

RESULTS

Twenty-five studies were identified, all of which contained incidence data on typhoid fever and 12 on paratyphoid fever. Five advanced surveillance systems contributed data on typhoid fever; 2 on paratyphoid fever. Regional typhoid fever incidence rates ranged from <0.1/100 000 cases/y in Central and Eastern Europe and Central Asia to 724.6/100 000 cases/y in Sub-Saharan Africa. Regional paratyphoid incidence rates ranged from 0.8/100 000 cases/y in North Africa/Middle East to 77.4/100 000 cases/y in Sub-Saharan Africa and South Asia. The estimated total number of typhoid fever episodes in 2010 was 13.5 million (interquartile range 9.1-17.8 million). The adjusted estimate accounting for the low sensitivity of blood cultures for isolation of the bacteria was 26.9 million (interquartile range 18.3-35.7 million) episodes. These findings are comparable to the most recent analysis of global typhoid fever morbidity, which reported crude and adjusted estimates of 10.8 million and 21.7 million typhoid fever episodes globally in 2000.

CONCLUSION

Typhoid fever remains a significant health burden, especially in low- and middle-income countries. Despite the availability of more recent data on both enteric fevers, additional research is needed in many regions, particularly Africa, Latin America and other developing countries.