Dengue in the Americas. A problem of regional health

The Aedes aegypti was almost eradicate from The Americas in the early sixties but reinfested the Region a few years later, and dengue transmission has become a major health problem. The Americas have been affected by dengue epidemics since the 1970s and hemorrhagic fever is becoming a threat for millions of people living in the tropical and subtropical areas of the continent. Resources to cope with the increasing transmission of different serotypes in the Region are scarce. Therefore a regional effort to prevent the dissemination of dengue hemorrhagic fever (DHF) is necessary. Public awareness and community participation must be promoted and enhanced in order to decrease the risk of DHF.     

The Epidemiology of Dengue in the Americas Over the Last Three Decades: A Worrisome Reality

We have reported the epidemic patterns of dengue disease in the Region of the Americas from 1980 through 2007. Dengue cases reported to the Pan American Health Organization were analyzed from three periods: 1980–1989 (80s), 1990–1999 (90s), and 2000–2007 (2000–7). Age distribution data were examined from Brazil, Venezuela, Honduras, and Mexico. Cases increased over time: 1,033,417 (80s) to 2,725,405 (90s) to 4,759,007 (2000–7). The highest concentrations were reported in the Hispanic Caribbean (39.1%) in the 80s shifting to the Southern Cone in the 90s (55%) and 2000–7 (62.9%). From 1980 through 1987, 242 deaths were reported compared with 1,391 during 2000–7. The most frequently isolated serotypes were DENV-1 and DENV-2 (90s) and DENV-2 and DENV-3 (2000–7). The highest incidence was observed among adolescents and young adults; dengue hemorrhagic fever incidence was highest among infants in Venezuela. Increasing dengue morbidity/mortality was observed in the Americas in recent decades.     

2013 Dengue Outbreaks in Singapore and Malaysia Caused by Different Viral Strains

Characterization of 14,079 circulating dengue viruses in a cross-border surveillance program, UNITEDengue, revealed that the 2013 outbreaks in Singapore and Malaysia were associated with replacement of predominant serotype. While the predominant virus in Singapore switched from DENV2 to DENV1, DENV2 became predominant in neighboring Malaysia. Dominance of DENV2 was most evident on the southern states where higher fatality rates were observed.     

Melioidosis in the Americas

Melioidosis is a potentially severe bacterial infection caused by Burkholderia pseudomallei. There has been growing awareness of the disease in the Americas, particularly since the Vietnam conflict when it was diagnosed in returning service personnel. Accidental laboratory exposure indicates the difficulty making a culture-based diagnosis when melioidosis has not been considered in the differential diagnosis. Melioidosis is most likely underdiagnosed in tropical Central and South America where conditions are more suited to persistence of B. pseudomallei in the environment. Recent melioidosis case clusters in northeastern Brazil highlight the threat posed to rural populations located far from specialist services. Increased clinical awareness of the disease and improvements in laboratory diagnostic methods are likely to bring wider recognition of melioidosis in the Americas.     

The Measles Laboratory Network in the region of the Americas

The success of measles eradication depends upon a laboratory network to rapidly analyze samples obtained as part of surveillance and case investigation. The Pan American Measles Laboratory Network was established in 1995. Major activities of the 22 participating laboratories include the rapid testing of serum samples to diagnose measles, analysis and recommendation of techniques to be used in serologic testing, training in virus isolation, and procurement and distribution of laboratory materials. In addition, a comprehensive quality-control program and an electronic communication network have been developed. Testing for rubella has also been incorporated. The Network has been crucial to the great progress made toward eradicating measles from the Western Hemisphere. The priority given to the laboratories in the Network must continue in order to ensure that the eradication goal is reached and that validation of the interruption of endemic transmission of measles is documented.     

Intra- and Interseasonal Autoregressive Prediction of Dengue Outbreaks Using Local Weather and Regional Climate for a Tropical Environment in Colombia

Dengue fever transmission results from complex interactions between the virus, human hosts, and mosquito vectors—all of which are influenced by environmental factors. Predictive models of dengue incidence rate, based on local weather and regional climate parameters, could benefit disease mitigation efforts. Time series of epidemiological and meteorological data for the urban environment of Cali, Colombia are analyzed from January of 2000 to December of 2011. Significant dengue outbreaks generally occur during warm-dry periods with extreme daily temperatures confined between 18°C and 32°C—the optimal range for mosquito survival and viral transmission. Two environment-based, multivariate, autoregressive forecast models are developed that allow dengue outbreaks to be anticipated from 2 weeks to 6 months in advance. These models have the potential to enhance existing dengue early warning systems, ultimately supporting public health decisions on the timing and scale of vector control efforts.     

Yellow fever in the Americas

Dutch slave traders brought yellow fever to the Americas from Africa during the mid-seventeenth century. For the next two and a half centuries, the disease terrorized seaports throughout the Americas. Proof of the mosquito hypothesis was delayed because of two aspects of the disease: patients are viremic only during the first several days of clinical illness, and most mosquitoes require about 2 weeks of viral incubation before becoming infectious. Control of Aedes aegypti in urban centers failed to eliminate the disease because of its transmission by tree-hole-breeding mosquitoes that spend their winged lives mainly in forest canopies. Yellow fever continues to be a significant public health problem in parts of South America and Africa.     

The prevalence of nonalcoholic fatty liver disease in the Americas

Nonalcoholic fatty liver disease (NAFLD) is an alarming public health problem. The disease is one of the main causes of chronic liver disease worldwide and is directly linked to the increased prevalence of obesity and type 2 diabetes mellitus (T2DM) in the general population. The worldwide prevalence of NAFLD has been estimated at 20-30%, but the prevalence is unknown in the Americas because of a lack of epidemiological studies. However, given the trends in the prevalence of diabetes and obesity, the prevalence of NAFLD and its consequences are expected to increase in the near future. The aim of the present study is to present the current data on the prevalence of NAFLD in the Americas. We performed an electronic search of the main databases from January 2000 to September 2013 and identified 356 reports that were reviewed. We focused on the epidemiology and prevalence of known NAFLD risk factors including obesity, T2DM, and the metabolic syndrome (MS). The prevalence of the MS was highest in the United States, Mexico, Costa Rica, Puerto Rico, Chile, and Venezuela. In addition, Puerto Rico, Guyana, and Mexico have the highest prevalence of T2DM in the Americas, while USA has the most people with T2DM. In conclusion, the prevalence rates of NAFLD and obesity were highest in the United States, Belize, Barbados, and Mexico.     

State of immunization in the Americas

Countries in the Americas have led the world in conquering infectious diseases preventable through vaccination. In 1971, the Western hemisphere achieved smallpox eradication. In 1991, the Americas were free of indigenous transmission of wild poliovirus. In 1998, overall regional vaccination coverage was 86% for diphtheria-pertussis-tetanus, 89% for oral poliovirus vaccine 3, 98% for bacille Calmette-Guérin vaccine, and 85% for measles. These figures confirm that most of the children in the Americas are protected against these diseases. The breakthroughs obtained in immunization have stimulated countries to promote new initiatives aimed at the control and eradication of other vaccine-preventable diseases and to introduce new vaccines into routine schedules. In the 21st century, vaccines will remain the most cost-effective means of preventing diseases and avoiding expensive treatment costs.     

Global Evolutionary History and Dynamics of Dengue Viruses Inferred from Whole Genome Sequences

Dengue is an arboviral disease caused by dengue virus (DENV), leading to approximately 25,000 deaths/year and with over 40% of the world’s population at risk. Increased international travel and trade, poorly regulated urban expansion, and warming global temperatures have expanded the geographic range and incidence of the virus in recent decades. This study used phylogenetic and selection pressure analyses to investigate trends in DENV evolution, using whole genome coding sequences from publicly available databases alongside newly sequenced isolates collected between 1963–1997 from Southeast Asia and the Pacific. Results revealed very similar phylogenetic relationships when using the envelope gene and the whole genome coding sequences. Although DENV evolution is predominantly driven by negative selection, a number of amino acid sites undergoing positive selection were found across the genome, with the majority located in the envelope and NS5 genes. Some genotypes appear to be diversifying faster than others within each serotype. The results from this research improve our understanding of DENV evolution, with implications for disease control efforts such as Wolbachia-based biocontrol and vaccine design.     

The emergence of HIV/AIDS in the Americas and beyond

HIV-1 group M subtype B was the first HIV discovered and is the predominant variant of AIDS virus in most countries outside of sub-Saharan Africa. However, the circumstances of its origin and emergence remain unresolved. Here we propose a geographic sequence and time line for the origin of subtype B and the emergence of pandemic HIV/AIDS out of Africa. Using HIV-1 gene sequences recovered from archival samples from some of the earliest known Haitian AIDS patients, we find that subtype B likely moved from Africa to Haiti in or around 1966 (1962-1970) and then spread there for some years before successfully dispersing elsewhere. A "pandemic" clade, encompassing the vast majority of non-Haitian subtype B infections in the United States and elsewhere around the world, subsequently emerged after a single migration of the virus out of Haiti in or around 1969 (1966-1972). Haiti appears to have the oldest HIV/AIDS epidemic outside sub-Saharan Africa and the most genetically diverse subtype B epidemic, which might present challenges for HIV-1 vaccine design and testing. The emergence of the pandemic variant of subtype B was an important turning point in the history of AIDS, but its spread was likely driven by ecological rather than evolutionary factors. Our results suggest that HIV-1 circulated cryptically in the United States for approximately 12 years before the recognition of AIDS in 1981.     

Multicomponent donor apheresis in the Americas

Multicomponent donor apheresis utilizes apheresis technology to collect combinations of red blood cells, platelets and plasma units. The United States has embraced this technology to the greatest extent of the countries in the Americas. As whole blood and apheresis collection have increased, so have the donor deferrals based on potential exposure to infectious agents. However, hemoglobin/hematocrit deferrals still remain the largest upfront deferral for volunteer donors. As the technology is refined in future years, multicomponent donor apheresis may become the predominant method of collecting blood products from donors.