The study of psychology is the study of mental behavior through different stages of life and illnesses. Not only does psychology cause you to use extraneous amounts of critical thinking, but it also covers the interesting topic of mental illnesses. Counseling psychology an interesting topic, within psychology. This large field in psychology is fascinating, because the psychologist is able to really focus in on the patient with a mental illness. Forensic psychology is another intriguing topic, as the psychologist gets to learn about different criminals and try to understand what goes on in their mind as they commit their crimes. perimental psychology Yellow fever, known historically as yellow jack, yellow plague, is an acute viral disease.
A safe and effective vaccine against yellow fever exists and some countries require vaccinations for travelers. with nearly 90% of these occurring in Africa. Since the 1980s, the number of cases of yellow fever has been increasing. This is believed to be due to fewer people being immune, more people living in cities, people moving frequently, and changing climate. Since the 17th century, several major outbreaks of the disease have occurred in the Americas, Africa, and Europe. Signs and symptoms
Yellow fever begins after an incubation period of three to six days. Most cases only cause a mild infection with fever, headache, chills, back pain, fatigue, loss of appetite, muscle pain, nausea, and vomiting. In these cases, the infection lasts only three to four days. In 15 percent of cases, however, people enter a second, toxic phase of the disease with recurring fever, this time accompanied by jaundice due to liver damage, as well as abdominal pain. Bleeding in the mouth, the eyes, and the gastrointestinal tract will cause vomit containing blood, hence the Spanish name for yellow fever, vomito negro .
The toxic phase is fatal in about 20% of cases, making the overall fatality rate for the disease 3%. In severe epidemics, the mortality may exceed 50%. Surviving the infection provides lifelong immunity, and normally there is no permanent organ damage. Cause Yellow fever is caused by the yellow fever virus, a 40- to 50-nm-wide enveloped RNA virus, the type species and namesake of the family Flaviviridae. The positive-sense, single-stranded RNA is around 11,000 nucleotides long and has a single open reading frame encoding a polyprotein.
Host proteases cut this polyprotein into three structural and seven nonstructural proteins ; the enumeration corresponds to the arrangement of the protein coding genes in the genome. Yellow fever belongs to the group of hemorrhagic fevers. The viruses infect, amongst others, monocytes, macrophages, and dendritic cells. They attach to the cell surface via specific receptors and are taken up by an endosomal vesicle. Inside the endosome, the decreased pH induces the fusion of the endosomal membrane with the virus envelope. The capsid enters the cytosol, decays, and releases the genome.
Receptor binding, as well as membrane fusion, are catalyzed by the protein E, which changes its conformation at low pH, causing a rearrangement of the 90 homodimers to 60 homotrimers. Three epidemiologically different infectious cycles occur, Pathogenesis After transmission from a mosquito, the viruses replicate in the lymph nodes and infect dendritic cells in particular. From there, they reach the liver and infect hepatocytes, which leads to eosinophilic degradation of these cells and to the release of cytokines. Necrotic masses known as Councilman bodies appear in the cytoplasm of hepatocytes.
Fatality may occur when cytokine storm, shock, and multiple organ failure follow. and lasts for at least 10 years. About 81% of people are still immune after 30 years. The attenuated live vaccine stem 17D was developed in 1937 by Max Theiler. In rare cases, although the disease does not yet occur there. To prevent introduction of the virus, some countries demand previous vaccination of foreign visitors if they have passed through yellow fever areas. Vaccination has to be proven in a vaccination certificate which is valid 10 days after the vaccination and lasts for 10 years.
A list of the countries that require yellow fever vaccination is published by the WHO. If the vaccination cannot be conducted for some reasons, dispensation may be possible. In this case, an exemption certificate issued by a WHO-approved vaccination center is required. Although 32 of 44 countries where yellow fever occurs endemically do have vaccination programmes, in many of these countries, less than 50% of their population is vaccinated. Another proposal is the absence of a slave trade to Asia on the scale of that to the Americas. The trans-Atlantic slave trade was probably the means of introduction into the Western hemisphere from Africa.
Worldwide, about 600 million people live in endemic areas. The WHO estimates 200,000 cases of disease and 30,000 deaths a year occur; the number of officially reported cases is far lower. An estimated 90% of the infections occur on the African continent. This appears to be especially virulent or infectious, as this type is often associated with major outbreaks. The three genotypes in East and Central Africa occur in areas where outbreaks are rare. Two recent outbreaks in Kenya and Sudan involved the East African genotype, which had remained unknown until these outbreaks occurred. In South America, two genotypes have been identified . d were first introduced into Brazil.
The date of introduction into South America appears to be 1822 . History The evolutionary origins of yellow fever most likely lie in Africa, with transmission of the disease from non-human primates to humans. The virus is thought to have originated in East or Central Africa and spread from there to West Africa. As it was endemic in Africa, the natives had developed some immunity to it. When an outbreak of yellow fever would occur in an African village where colonists resided, most Europeans died, while the native population usually suffered nonlethal symptoms resembling influenza.
This phenomenon, in which certain populations develop immunity to yellow fever due to prolonged exposure in their childhood, is known as acquired immunity. The virus, as well as the vector A. aegypti, were probably transferred to North and South America with the importation of slaves from Africa, part of the Columbian Exchange following European exploration and colonization. The first definitive outbreak of yellow fever in the New World was in 1647 on the island of Barbados. An outbreak was recorded by Spanish colonists in 1648 in the Yucatan Peninsula, where the indigenous Mayan people called the illness xekik .
In 1685, Brazil suffered its first epidemic, in Recife. The first mention of the disease by the name “yellow fever” occurred in 1744. McNeill argues that the environmental and ecological disruption caused by the introduction of sugar plantations created the conditions for mosquito and viral reproduction, and subsequent outbreaks of yellow fever. Deforestation reduced insectivorous bird populations and other creatures that fed on mosquitoes and their eggs. Although yellow fever is most prevalent in tropical-like climates, the northern United States were not exempted from the fever.
The first outbreak in English-speaking North America occurred in New York in 1668, and a serious one afflicted Philadelphia in 1793. English colonists in Philadelphia and the French in the Mississippi River Valley recorded major outbreaks in 1669, as well as those occurring later in the 18th and 19th centuries. The southern city of New Orleans was plagued with major epidemics during the 19th century, most notably in 1833 and 1853. At least 25 major outbreaks took place in the Americas during the 18th and 19th centuries, including particularly serious ones in Cartagena in 1741, Cuba in 1762 and 1900, Santo Domingo in 1803, and Memphis in 1878.
Major outbreaks have also occurred in southern Europe. Gibraltar lost many to outbreaks in 1804, in 1814, and again in 1828. Barcelona suffered the loss of several thousand citizens during an outbreak in 1821. Urban epidemics continued in the United States until 1905, with the last outbreak affecting New Orleans. In Colonial times and during the Napoleonic Wars, the West Indies were known as a particularly dangerous posting for soldiers due to the presence of yellow fever. The mortality rate in British garrisons in Jamaica was seven times that of garrisons in Canada, mostly because of yellow fever and other tropical disease like malaria.
Both English and French forces posted there were decimated by the “yellow jack. ” Wanting to regain control of the lucrative sugar trade in Saint-Domingue, and with an eye on regaining France’s New World empire, Napoleon sent an army under the command of his brother-in-law to Saint-Domingue to seize control after a slave revolt. The historian J. R. McNeill asserts that yellow fever accounted for about 35,000 to 45,000 casualties of these forces during the fighting. Only one-third of the French troops survived for withdrawal and return to France.
Napoleon gave up on the island, and in 1804 Haiti proclaimed its independence as the second republic in the Western Hemisphere. The yellow fever epidemic of 1793 in Philadelphia, which was then the capital of the United States, resulted in the deaths of several thousand people, more than 9% of the population. The national government fled the city, including President George Washington. Additional yellow fever epidemics struck Philadelphia, Baltimore, and New York in the 18th and 19th centuries, and traveled along steamboat routes from New Orleans.
They caused some 100,000–150,000 deaths in total. In 1853, Cloutierville, Louisiana, had a late summer outbreak of yellow fever that quickly killed 68 of the 91 inhabitants. A local doctor concluded that the infectious agents arrived in a package from New Orleans. In 1858, St. Matthew’s German Evangelical Lutheran Church in Charleston, South Carolina, suffered 308 yellow fever deaths, reducing the congregation by half. In 1873, Shreveport, Louisiana, lost almost a quarter of its population to yellow fever.
In 1878, about 20,000 people died in a widespread epidemic in the Mississippi River Valley. That year, Memphis had an unusually large amount of rain, which led to an increase in the mosquito population. The result was a huge epidemic of yellow fever. The steamship John D. Porter took people fleeing Memphis northward in hopes of escaping the disease, but passengers were not allowed to disembark due to concerns of spreading yellow fever. The ship roamed the Mississippi River for the next two months before unloading her passengers.
The last major U. S. tbreak was in 1905 in New Orleans. Ezekiel Stone Wiggins, known as the Ottawa Prophet, proposed that the cause of a yellow fever epidemic in Jacksonville, Florida, in 1888, was astronomical. The planets were in the same line as the sun and earth and this produced, besides Cyclones, Earthquakes, etc. , a denser atmosphere holding more carbon and creating microbes. Mars had an uncommonly dense atmosphere, but its inhabitants were probably protected from the fever by their newly discovered canals, which were perhaps made to absorb carbon and prevent the disease.