'Diseases' have also undergone evolution along with the human race. In the ancient times people condemned diseases are the result of enraged gods or some wicked spirits. An epidemic disease causes illness in populations in the particular geographical area at the same instance of time. The source of the epidemic outburst may be viral or bacterial. In pandemic disease the illness affects large geographical areas worldwide. So the distinguishing features between a pandemic and epidemic is that an epidemic is confined to much smaller region like a village, a town or a nation compared to pandemic diseases which infest several nations worldwide and the death rate is higher in pandemics compared to epidemics.
Many epidemic and pandemic diseases have wiped out large proportions of populations over the centuries. Outburst of smallpox is an example of viral epidemic known far back in time. Its first descriptions were in china in 1122 B.C. The disease hit Europe over fifteen years decimating one third of the population. Edward Jenner in 1796 formulated the vaccine for small pox virus using pustules from cowpox lesions. Later in the year 1979 WHO (World Health Organisation) announced officially 'smallpox' as eradicated from the whole world.
Plague (so called bubonic plague or black plague) is caused by Yersinia pestis, a bacterium. The illness is transmitted to people by means of the bite from a rodent flea and also the disease could be transmitted by contact with the infected animal. It killed millions of people in Europe during the Middle Ages and had returned periodically striking people worldwide and it is considered as one of the worst pandemics ever.
Influenza is a viral epidemic. Various antigenic forms of influenza virus has been striking periodically from the middle ages during sixteenth, eighteenth and twentieth centuries and continue to occur although its first outburst description dates back to 412 B.C by Hippocrates. The influenza virus can change its outer surface protein constitution as the immunity acquired to the illness in one year is not sufficient against the evolved virus arising few years later. The epidemics in 1918 by influenza virus is one of the worst known calamitous event in the past causing the deaths of about 20 million people.
Cholera is caused by the bacterium Vibrio cholerae. Unhygienic management of food and drinking water causes the illness. The first representation of the epidemics dates back in time in India (1563) and by the year 1817 cholera had become pandemic.
Tuberculosis epidemic is caused by the bacteria Mycobacterium tuberculosis. The rate of occurrence of the disease is increasing every year and killing an estimated 2 million people worldwide each year. The overuse or misuse of antibiotic drugs has lead to the emergence of multidrug resistant forms of the bacterium which are unable to treat. The spread of the resistant strains increases as the carriers of these forms move worldwide dispersing the infection.
HIV (human immunodeficiency virus) causes AIDS the disease in which an individuals immune system is destroyed. It is an epidemic caused by the virus that came to light in the later half of the twentieth century. The first recorded death due to HIV infection was recorded in 1959 in Congo. The epidemic has spread then to become pandemic worldwide. The modern ability of mankind to travel all over the globe and the latent period of the virus infection contributes to the spreading of the virus and AIDS has become pandemic spreading among all cultural , racial economic and geographical categories.
Scientists have recently found out that some of the common diseases are caused by bacteria. Common examples include stomach ulcer which has been recognized to be caused by Helicobater pylori and some of the heart ailment discovered to be caused by the reaction of the human immune system to infection by bacteria Chlamydia. These types of diseases are called chronic infection and differ from other bacterial and viral epidemics because they do not either appear or fade in short time period. These chronic infections are present for long period of time causing non-stop pandemics of the particular disease.
Epidemics and pandemics have been known throughout recorded human history. These incidences are less in modern day cities due to better sanitary conditions and standards of housing. But the epidemics like typhoid, dysentery, typhus, cholera etc are still present in the undeveloped parts of the world where sanitation is very poor. Today, the world is known as a global village due to interconnection and humans travel throughout the world. This interconnected world makes it easier for diseases to spread rapidly and over greater distances from the point of origin. Therefore it is important to understand the insights of these maladies for preventing and controlling epidemic and pandemic breakouts.
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