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Query: UMLS:C0344329 (collapse)
 28,634 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mystery has long surrounded the collapse of the Classic lowland Mayan civilization of the Peten region in Guatemala. Recent population reconstructions derived from archaeological evidence from the central lowlands show population declines from urban levels of between 2.5 and 3.5 million to around 536,000 in the two hundred year interval between 800 A.D. and 1000 A.D., the period known as the Classic Maya Collapse. A steady, but lesser rate of population decline continued until the time of European contact. When knowledge of the ecology and epidemiology of yellow fever and its known mosquito vectors are compared with what is known of the ecological conditions of lowland Guatemala as modified by the Classic Maya, provocative similarities are observed. When infection and mortality patterns of more recent urban yellow fever epidemics are used as models for a possible series of Classic Maya epidemics, a correlation is noted between the modeled rate of population decline for a series of epidemics, and population decline figures reconstructed from archaeological evidence.
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PMID:Yellow fever: ecology, epidemiology, and role in the collapse of the Classic lowland Maya civilization. 864 25

In the last two decades, yellow fever re-emerged with vehemence to constitute a major public health problem in Africa. The disease has brought untold hardship and indescribable misery among different populations in Africa. It is one of Africa's stumbling blocks to economic and social development. Despite landmark achievements made in the understanding of the epidemiology of yellow fever disease and the availability of a safe and efficacious vaccine, yellow fever remains a major public health problem in both Africa and America where the disease affects annually an estimated 200,000 persons causing an estimated 30,000 deaths. Africa contributes more than 90% of global yellow fever morbidity and mortality. Apart from the severity in morbidity and mortality, which are grossly under reported, successive outbreaks of yellow fever and control measures have disrupted existing health care delivery services, overstretched scarce internal resources, fatigued donor assistance and resulted in gross wastage of vaccines. Recent epidemics of yellow fever in Africa have affected predominantly children under the age of fifteen years. Yellow fever disease can be easily controlled. Two examples from Africa suffice to illustrate this point. Between 1939 and 1952, yellow fever virtually disappeared in parts of Africa, where a systematic mass vaccination programme was in place. More recently, following the 1978-1979 yellow fever epidemic in the Gambia, a mass yellow fever vaccination programme was carried out, with a 97% coverage of the population over 6 months of age. Subsequently, yellow fever vaccination was added to the EPI Programme. The Gambia has since then maintained a coverage of over 80%, without a reported case of yellow fever, despite being surrounded by Senegal which experienced yellow fever outbreaks in 1995 and 1996. The resurgence of yellow fever in Africa and failure to control the disease has resulted from a combination of several factors, including: 1) collapse of health care delivery systems; 2) lack of appreciation of the full impact of yellow fever disease on the social and economic development of the affected communities; 3) insufficient political commitment to yellow fever control by governments of endemic countries; 4) poor or inadequate disease surveillance; 5) inappropriate disease control measures, and 6) preventable poverty coupled with misplaced priorities in resource allocation. Yellow fever can be controlled in Africa within the next 10 years, if African governments seize the initiative for yellow fever control by declaring an uncompromising resolve to control the disease, the governments back up their resolve with an unrelenting commitment and unwavering political will through adequate budgetary allocations for yellow fever control activities, and international organisations, such as WHO, UNICEF, GAVI, etc., provide support and technical leadership and guidance to yellow fever at risk countries. Over a ten-year period, of stage-by-stage mass yellow fever vaccination campaigns, integrated with successful routine immunisation, Africa can bring yellow fever under control. Subsequently, for yellow fever to cease being a public health problem, Africa must maintain at least an annual 80% yellow fever vaccine coverage of children under the age of 1 year, and sustain a reliable disease surveillance system with a responsive disease control programme. This can be achieved at an affordable annual expenditure of less than US$1.00 per person per year, with a reordering of priorities.
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PMID:Yellow fever in Africa: public health impact and prospects for control in the 21st century. 1215 84

A medical officer for the Expanded Program on Immunization (EPI) of the World Health Organization (WHO) calls for staff at all health facilities to screen and, if appropriate, immunize every infant, child, and woman of reproductive age attending health facilities. Routine immunization services tend to miss many women and children who should be immunized. Three important components comprise the health team approach needed to avoid missed opportunities: awareness to screen, a well-organized referral system within each health facility, and regular availability of vaccines. In the health facility, the nonimmunized child is at risk of contracting measles, so all such children should be immunized before they leave the health facility. The WHO/EPI medical officer presents five ways to avoid missed opportunities: screen and immunize at every opportunity, administer all required vaccines, stress real and avoid false contraindications, train staff, and open new vials of vaccine when needed. Contraindications to immunization include severe adverse reactions after a dose of vaccine (collapse or shock, convulsions without fever, anaphylaxis, or encephalitis/encephalopathy), neurological disease (for vaccines containing whole cell pertussis), immune deficiency diseases or immunosuppression due to drugs (generally for live vaccines), and symptomatic HIV infections (for BCG or yellow fever vaccines). The following conditions do not preclude immunization: minor illnesses (e.g., upper respiratory infections); allergy, asthma, hay fever, or "snuffles"; prematurity, small-for-date infants; malnutrition; breast feeding; family history of convulsions; treatment with antibiotics, low-dose corticosteroids, or locally acting steroids; eczema or localized skin infection; chronic diseases of the heart, lung, kidney, or liver; stable neurological conditions (e.g., Down syndrome), and history of jaundice after birth. WHO/EPI has an exit survey for use at district-level clinics or hospitals available so program managers can learn if they are missing chances to immunize children.
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PMID:Opportunities to immunise. 1229 31

Viruses are important pathogens in tropical areas; most of them, especially the tropical hemorrhagic fevers, produce mucocutaneous manifestations. More than any other kind of pathogen, viruses have the possibility for being widespread, since they have a greater probability of mutation than do bacteria, can cross species barriers easily, and infect both human beings and animals in habitats with a great biodiversity. Tropical habitats also have been subject to major ecologic changes in the last few decades, exposing humans to direct contact with these viruses and allowing hemorrhagic fevers due to new emergent viruses such as flaviviruses, filoviruses, arenaviruses, and hantaviruses to become major threats to public health. The collapse of eradication programs in many countries, as well as population increases and ecologic modifications, have led to the spread of dengue and yellow fever to large portions of the world owing to the dissemination of vectors, especially mosquitoes, with broad ecologic ranges. Viruses previously restricted to some geographic areas, such as Rift Valley fever, Crimean-Congo hemorrhagic fever, West Nile fever, and monkeypox are now affecting new countries and populations. Other viruses such as herpes B infection often affect travelers and animal handlers in most parts of the world. Dermatologic lesions occur in all these diseases and can facilitate a rapid diagnosis, leading to control of the virus and helping prevent possible outbreaks.
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PMID:Tropical dermatology: viral tropical diseases. 1558 19

The use ot a polyvalent immune serum ot nign potency in tne treatment of an experimental infection of guinea pigs with Leptospira icteroides was found to be of definite advantage in checking the progress of the infection. When administered during the period of incubation the serum was found capable of completely preventing the development of the disease, although on subsequent examination hemorrhagic lesions of greater or less number and extent were found in the lungs of the guinea pigs which survived. Moreover, the serum modified the course of the disease and when used in the early stages of infection prevented a fatal outcome. Employed at a later stage, however, when jaundice and nephritis had been present for several days and the animal was near collapse, the serum had no perceptible beneficial effect. This was, of course, to be expected in view of the incidence of various pathological phases of this disease-nephritis, hepatitis, and other toxic symptoms in succession. In man the clinical manifestations are more gradual and distinct than in the guinea pig, yet the yellow fever patient whose temperature is sub-normal, and who has reached the stage of hemorrhages from the gums, nose, stomach, and intestines, and of uremia and cholemia, would seem to have little or no chance of deriving benefit from the use of a specific immune serum. This latter assumption would probably hold irrespective of the relation which Leptospira icteroides proves to have to the etiology of yellow fever.
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PMID:ETIOLOGY OF YELLOW FEVER : XI. SERUM TREATMENT OF ANIMALS INFECTED WITH LEPTOSPIRA ICTEROIDES. 1986 94

Despite the devastating impact of mosquito-borne illnesses on human health, surprisingly little is known about mosquito developmental biology, including development of the olfactory system, a tissue of vector importance. Analysis of mosquito olfactory developmental genetics has been hindered by a lack of means to target specific genes during the development of this sensory system. In this investigation, chitosan/siRNA nanoparticles were used to target semaphorin-1a (sema1a) during olfactory system development in the dengue and yellow fever vector mosquito Aedes aegypti. Immunohistochemical analyses and anterograde tracing of antennal sensory neurons, which were used to track the progression of olfactory development in this species, revealed antennal lobe defects in sema1a knockdown fourth instar larvae. These findings, which correlated with a larval odorant tracking behavioral phenotype, identified previously unreported roles for Sema1a in the developing insect larval olfactory system. Analysis of sema1a knockdown pupae also revealed a number of olfactory phenotypes, including olfactory receptor neuron targeting and projection neuron defects coincident with a collapse in the structure and shape of the antennal lobe and individual glomeruli. This study, which is to our knowledge the first functional genetic analysis of insect olfactory development outside of D. melanogaster, identified critical roles for Sema1a during Ae. aegypti larval and pupal olfactory development and advocates the use of chitosan/siRNA nanoparticles as an effective means of targeting genes during post-embryonic Ae. aegypti development. Use of siRNA nanoparticle methodology to understand sensory developmental genetics in mosquitoes will provide insight into the evolutionary conservation and divergence of key developmental genes which could be exploited in the development of both common and species-specific means for intervention.
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PMID:Disruption of Aedes aegypti olfactory system development through chitosan/siRNA nanoparticle targeting of semaphorin-1a. 2369 8

The recent onset of epidemics caused by viruses such as Ebola, Marburg, Nipah, Lassa, coronavirus, West-Nile encephalitis, Saint Louis encephalitis, human immunodeficiency virus, dengue, yellow fever and Venezuelan hemorrhagic fever alerts about the risk these agents represent for the global health. Chikungunya virus represents a new threat. Surged from remote African regions, this virus has become endemic in the Indic ocean basin, the Indian subcontinent and the southeast of Asia, causing serious epidemics in Africa, Indic Ocean Islands, Asia and Europe. Due to their epidemiological and biological features and the global presence of their vectors, chikungunya represents a serious menace and could become endemic in the Americas. Although chikungunya infection has a low mortality rate, its high attack ratio may collapse the health system during epidemics affecting a sensitive population. In this paper, we review the clinical and epidemiological features of chikungunya fever as well as the risk of its introduction into the Americas. We remark the importance of the epidemiological control and mosquitoes fighting in order to prevent this disease from being introduced into the Americas.
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PMID:[Chikungunya fever - A new global threat]. 2508 11