Measles eradication: experience in the Americas.
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In 1994, the Ministers of Health from the Region of the Americas targeted measles for eradication from the Western Hemisphere by the year 2000. To achieve this goal, the Pan American Health Organization (PAHO) developed an enhanced measles eradication strategy. First, a one-time-only "catch-up" measles vaccination campaign is conducted among children aged 9 months to 14 years. Efforts are then made to vaccinate through routine health services ("keep-up") at least 95% of each newborn cohort at 12 months of age. Finally, to assure high population immunity among preschool-aged children, indiscriminate "follow-up" measles vaccination campaigns are conducted approximately every 4 years. These vaccination activities are accompanied by improvements in measles surveillance, including the laboratory testing of suspected measles cases. The implementation of the PAHO strategy has resulted in a marked reduction in measles incidence in all countries of the Americas. Indeed, in 1996 the all-time regional record low of 2109 measles cases was reported. There was a relative resurgence of measles in 1997 with over 20,000 cases, due to a large measles outbreak among infants, preschool-aged children and young adults in Sao Paulo, Brazil. Contributing factors for this outbreak included: low routine infant vaccination coverage, failure to conduct a "follow-up" campaign, presence of susceptible young adults, and the importation of measles virus, apparently from Europe. PAHO's strategy has been effective in interrupting measles virus circulation. This experience demonstrates that global measles eradication is an achievable goal using currently available measles vaccines. (+info)
Linguistic diversity of the Americas can be reconciled with a recent colonization.
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The Americas harbor a very great diversity of indigenous language stocks, many more than are found in any other continent. J. Nichols [(1990) Language 66, 475-521] has argued that this diversity indicates a great time depth of in situ evolution. She thus infers that the colonization of the Americas must have begun around 35,000 years ago. This estimate is much earlier than the date for which there is strong archaeological support, which does not much exceed 12,000 years. Nichols' assumption is that the diversity of linguistic stocks increases linearly with time. This paper compares the major continents of the world to show that this assumption is not correct. In fact, stock diversity is highest in the Americas, which are by consensus the youngest continents, intermediate in Australia and New Guinea, and lowest in Africa and Eurasia where the time depth is greatest. If anything, then, after an initial radiation, stock diversity decreases with time. A simple model is outlined that predicts these dynamics. It assumes that early in the peopling of continents, there are many unfilled niches for communities to live in, and so fissioning into new lineages is frequent. As the habitat is filled up, the rate of fissioning declines and lineage extinction becomes the dominant evolutionary force. (+info)
Evolution and origins of tobamoviruses.
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More than a dozen tobamoviruses are known. In nature, each species probably survives by moving between several closely related host species. Each infected plant contains a population of variants, but in most host populations the tobamovirus population is stable. The phylogenetic relationships of tobamovirus species broadly correlate with those of their angiosperm hosts. The simplest explanation for this correlation is that they have coevolved with the angiosperms, and hence, like them, are about 120-140 million years old. Gene sequence differences between species also indicate that the tobamoviruses are an ancient genus. Their gene sequences, and the protein motifs they encode, link them to tobraviruses, hordeiviruses and soil-borne wheat mosaic virus, more distantly to the tricornaviruses, and even to hepatitis virus E and other furoviruses, rubiviruses and alphaviruses. Their progenitors may have been associated with charophycean algae, and perhaps also plasmodiophoromycete fungi. (+info)
Interspecies transfer of female mitochondrial DNA is coupled with role-reversals and departure from neutrality in the mussel Mytilus trossulus.
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Mussels of the genus Mytilus have distinct and highly diverged male and female mitochondrial DNA (mtDNA) genomes with separate routes of inheritance. Previous studies of European populations of Mytilus trossulus demonstrated that 33% of males are heteroplasmic for a second mtDNA genome of increased length and that hybridization with Mytilus edulis does not block mtDNA introgression, in contrast to reports for American populations. Here, we demonstrate that the female mtDNA type of M. edulis has replaced the resident female mtDNA type of European M. trossulus. This is supported by COIII sequence data indicating that the female mtDNA of European M. trossulus is very similar to that of M. edulis and that in phylogenetic trees, the mtDNAs of these two species cluster together but separately from American M. trossulus sequences, the latter not being disturbed by introgressive hybridization. We also provide evidence that the mtDNA genome of increased length found in heteroplasmic males of European M. trossulus derives from a recent partition of an introgressed M. edulis female type into the male route of transmission. Neutrality tests reveal that European populations of M. trossulus display an excess of replacement polymorphism within the female mtDNA type with respect to conspecific American populations, as well as a significant excess of rare variants, of a similar magnitude to those previously reported for the invading European M. edulis mtDNA. Results are consistent with a nearly neutral model of molecular evolution and suggest that selection acting on European M. trossulus mtDNA is largely independent of the nuclear genetic background. (+info)
Suicide, religion, and socioeconomic conditions. An ecological study in 26 countries, 1990.
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STUDY OBJECTIVE: Relative risks are frequently assumed to be stable across populations but this may not apply in psychiatric epidemiology where sociocultural context may modify them. Such ecological effect modification will give curved associations between aggregated risk factor and outcome. This was examined in connection with the ecological association between suicide rates and an aggregate index of religiosity. DESIGN: Ecological study of associations between suicide rates and an index of religiosity, adjusted for socioeconomic variation. The effect of stratification of the study sample according to levels of religiosity, was examined. SETTING: 26 European and American countries. SUBJECTS: Interview data from 37,688 people aggregated by country. OUTCOME MEASURES: Age and sex specific (1986-1990) suicide rates. MAIN RESULT: Adjusted for socioeconomic variation, negative associations of male suicide rates with religiosity were apparent in the 13 least religious countries only (test for interaction F (1, 25) = 5.6; p = 0.026). Associations between religiosity and female suicide rates did not vary across countries. CONCLUSION: The bent ecological association was apparent only after adjustment for socioeconomic variation suggesting that, rather than confounding, ecological modification of individual level links between religion and male (but not female) suicide risk is the responsible mechanism. This concurs with micro-level findings suggesting that suicide acceptance depends not only on personal but also on contextual levels of religious belief, and that men are more sensitive to this phenomenon than women. In psychiatric epidemiology, relative risks vary with the exposure's prevalence. This has important implications for research and prevention. (+info)
Genetic structure of natural populations of Escherichia coli in wild hosts on different continents.
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Current knowledge of genotypic and phenotypic diversity in the species Escherichia coli is based almost entirely on strains recovered from humans or zoo animals. In this study, we analyzed a collection of 202 strains obtained from 81 mammalian species representing 39 families and 14 orders in Australia and the Americas, as well as several reference strains; we also included a strain from a reptile and 10 from different families of birds collected in Mexico. The strains were characterized genotypically by multilocus enzyme electrophoresis (MLEE) and phenotypically by patterns of sugar utilization, antibiotic resistance, and plasmid profile. MLEE analysis yielded an estimated genetic diversity (H) of 0.682 for 11 loci. The observed genetic diversity in this sample is the greatest yet reported for E. coli. However, this genetic diversity is not randomly distributed; geographic effects and host taxonomic group accounted for most of the genetic differentiation. The genetic relationship among the strains showed that they are more associated by origin and host order than is expected by chance. In a dendrogram, the ancestral cluster includes primarily strains from Australia and ECOR strains from groups B and C. The most differentiated E. coli in our analysis are strains from Mexican carnivores and strains from humans, including those in the ECOR group A. The kinds and numbers of sugars utilized by the strains varied by host taxonomic group and country of origin. Strains isolated from bats were found to exploit the greatest range of sugars, while those from primates utilized the fewest. Toxins are more frequent in strains from rodents from both continents than in any other taxonomic group. Strains from Mexican wild mammals were, on average, as resistant to antibiotics as strains from humans in cities. On average, the Australian strains presented a lower antibiotic resistance than the Mexican strains. However, strains recovered from hosts in cities carried significantly more plasmids than did strains isolated from wild mammals. Previous studies have shown that natural populations of E. coli harbor an extensive genetic diversity that is organized in a limited number of clones. However, knowledge of this worldwide bacterium has been limited. Here, we suggest that the strains from a wide range of wild hosts from different regions of the world are organized in an ecotypic structure where adaptation to the host plays an important role in the population structure. (+info)
In collaboration with the World Health Organization (WHO), the WHO international network of collaborating laboratories, and state and local health departments, CDC conducts surveillance to monitor influenza activity and to detect antigenic changes in the circulating strains of influenza viruses. From October 1998 through April 1999, influenza activity was moderate to severe in the Northern Hemisphere. Influenza A(H3N2) viruses predominated but influenza type B viruses were isolated more frequently than influenza A in some countries. Influenza A(H1N1) viruses were isolated from sporadic cases in Asia, Europe, and North America, and from outbreaks in South America. Since May 1999, influenza activity associated primarily with influenza A(H3N2) viruses has peaked and is declining in the Southern Hemisphere. This report summarizes worldwide influenza activity during May-September 1999 and the antigenic characteristics of influenza isolates collected during May-August 1999. (+info)
Status of national diabetes programmes in the Americas.
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Reported are the responses in the latter half of 1997 of all ministries of health in the Region of the Americas to the Declaration of the Americas on Diabetes, which was adopted by the Directing Council of the Pan American Health Organization (PAHO) in 1996 as a basis for national programme development in diabetes. The short-term targets were the designation of national focal points, the preparation of national estimates of the disease burden, and the development and implementation of national strategies and plans to deal with diabetes. The survey found that most countries recognized diabetes as a significant public health problem. In terms of global relevance, a number of lessons have been learned from this exercise: the role of broadly based participation in gaining recognition at the national health policy level; the wide acceptance of an integrated programme model; the relevance of process-related targets to achieve short-term success; and the critical role of having a designated focal point within the managerial approach. (+info)