This book on "Human Diseases" is written with a view to meet curricular requirements of students at undergraduate and post graduate levels of Indian Universities. Diseases are illnesses impairing the normal physiological functioning of living organisms. The causative agents are virus, bacteria, protozoans, helminthes and others. The diseases chosen for this book are: measles, smallpox, chickenpox, AIDS, Ebola, Dengue, cholera, leprosy, tuberculosis, typhoid, malaria, amoebiasis, Diarrhoea, Filariasis, Cancer and Jaundice. The text describes causative agents, signs and symptoms, diagnosis, prevention, treatment, epidemiology and history of all 16 diseases. A table containing these factors has also been included for the convenience of readers to have an immediate idea about these human diseases.
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Sasmita Panda was born in 1982 and graduated in 2002 from Godavaris Mahavidyalaya, Banpur at Utkal University, Odisha. She completed her P.G. in Zoology in 2004 and her M. Phil. in 2013 from Khallikote College at Berhampur University. She has been teaching Zoology at different U.G. Colleges since 2006. Now serving as lecturer in zoology at Jatni College, Panda has published several articles in research journals of national and international repute. She has also co-authored books like "Employment Through Aquaculture", "Biology of Wild Animals", "Wild Animals of India" and "Earning Animals", meant for students of undergraduate and post-graduate level. Additionally, she edited a book entitled "Water for Survival".
Dr. S.N. Padhi, born in 1953, obtained his B.Sc. degree in 1973, his P.G. in 1975 and his Ph.D. in 1981 at Berhampur University. He devoted his time in teaching and research in different Govt. and Non-Govt. Colleges of Odisha since 1978. He has completed different research projects and published numerous research articles as well as edited many souvenirs of State level and National-level seminars funded by U.G.C., OBA and other Agencies. He is a recipient of the Prof. Amulya Kumar Panda Royal Teacher Award 2011 instituted by the Royal College of Science and Technology, Bhubaneswar. Furthermore, he edited a book on "Application Of Biology for Self employment" and co-authored a book on Fishery entitled "Employment Through Aquaculture", as well as "Biology of Wild Animals", "Wild Animals of India" and "Earning Animals", meant for students of undergraduate and post-graduate level. He has also edited a book entitled "Water for Survival". He is a recipient of the Emeritus fellowship by the University Grants Commission.
Chapter 2: SMALLPOX:
By Sasmita Panda.
Smallpox is an extremely contagious and deadly viral disease caused by Variola virus for which there is no known cure. The last known case occurred in the United States in 1949 and due to worldwide vaccination programs, this disease has been completely eradicated. Smallpox is also known as variola. Since the time of ancient Egypt, smallpox has proven to be one of the most devastating diseases to humankind. Widespread smallpox epidemics and huge death tolls fill the pages of our history books. The first smallpox vaccine was created in 1758. However, the disease continued to infect and kill people on a widespread basis for another 200 years. The World Health Organization (WHO) implemented a strict vaccination standard in order to slow the infection rate. The last known natural case occurred in 1977 in Somalia. By 1980, the WHO declared that smallpox had been completely eradicated, although Government and health agencies still have stashes of smallpox virus for research purposes. People no longer receive routine smallpox vaccinations. The smallpox vaccine can have potentially fatal side effects, so only the people who are at high risk of exposure get the vaccine.
Historical accounts show that when someone was infected with the smallpox virus, they had no symptoms for between seven and 17 days. However, once the incubation period (or virus development phase) was over, the following flu-like symptoms occurred:
Severe back pain.
These symptoms would go away within two to three days. Then the patient would feel better. However, just as the patient started to feel better, a rash would appear. The rash started on the face and then spread to the hands, forearms, and the main part of the body. The person would be highly contagious until the rash disappeared.
Within two days of appearance, the rash would develop into abscesses that filled with fluid and pus. The abscesses would break open and scab over. The scabs would eventually fall off, leaving pit mark scars. Until the scabs fell off, the person remained contagious.
Complications of smallpox arise most commonly in the respiratory system and range from simple bronchitis to fatal pneumonia. Respiratory complications tend to develop on about the eighth day of the illness and can be either viral or bacterial in origin. Secondary bacterial infection of the skin is a relatively uncommon complication of smallpox. When this occurs, the fever usually remains elevated.
Other complications include encephalitis (1 in 500 patients), which is more common in adults and may cause temporary disability; permanent pitted scars, most notably on the face; and complications involving the eyes (2 percent of all cases). Pustules can form on the eyelid, conjunctiva, and cornea, leading to complications such as conjunctivitis, keratitis, corneal ulcer, iritis, iridocyclitis, and optic atrophy. Blindness results in approximately 35 percent to 40 percent of eyes affected with keratitis and corneal ulcer. Haemorrhagic smallpox can cause subconjunctival and retinal haemorrhages. In 2 to 5 percent of young children with smallpox, virions reach the joints and bone, causing osteomyelitis variolosa. Lesions are symmetrical, most common in the elbows, tibia, and fibula, and characteristically cause separation of an epiphysis and marked periosteal reactions. Swollen joints limit movement, and arthritis may lead to limb deformities, ankylosis, malformed bones, flail joints, and stubby fingers.
One of the reasons smallpox was so dangerous and deadly is because it's an airborne disease. Airborne diseases tend to spread fast. Coughing, sneezing, or direct contact with any bodily fluids could spread the smallpox virus. In addition, sharing contaminated clothing or bedding could lead to infection.
TYPES OF SMALLPOX:
There were two common and two rare forms of smallpox. The two common forms were known as variola minor and variola major. Variola minor was a less fatal type of smallpox. The Centers for Disease Control and Prevention (CDC) estimate that only 1 percent of those infected died. However, it was less common than variola major. The CDC estimates that 90 percent of smallpox cases were variola major. Historically, this type of smallpox killed 30 percent of those infected. The two rare forms of smallpox were known as haemorrhagic and malignant. Both of these rare forms of smallpox carried a very high fatality rate. Hemorrhagic smallpox caused organs to leak blood into the mucous membranes and skin. Malignant smallpox lesions did not develop into pustules or pus-filled bumps on the skin. Instead, they remained soft and flat throughout the entire illness.
Smallpox is an airborne viral disease mainly spread by direct and fairly prolonged face-to-face contact between people. Smallpox patients became contagious once the first sores appeared in their mouth and throat (early rash stage). They spread the virus when they coughed or sneezed and droplets from their nose or mouth spread to other people. They remained contagious until their last smallpox scab fell off. These scabs and the fluid found in the patient's sores also contained the variola virus. The virus can spread through these materials or through the objects contaminated by them, such as bedding or clothing. People who cared for smallpox patients and washed their bedding or clothing had to wear gloves and take care to not get infected. Rarely, smallpox has spread through the air in enclosed settings, such as a building (airborne route). Smallpox can be spread by humans only. Scientists have no evidence that smallpox can be spread by insects or animals.
Smallpox is defined as an illness with acute onset of fever equal to or greater than 38.3 °C (101 °F) followed by a rash characterized by firm, deep seated vesicles or pustules in the same stage of development without other apparent cause. If a clinical case is observed, smallpox is confirmed using laboratory tests.
Microscopically, pox viruses produce characteristic cytoplasmic inclusions, the most important of which are known as Guarnieri bodies, and are the sites of viral replication. Guarnieri bodies are readily identified in skin biopsies stained with hematoxylin and eosin, and appear as pink blobs. They are found in virtually all pox virus infections but the absence of Guarnieri bodies cannot be used to rule out smallpox. The diagnosis of an orthopox virus infection can also be made rapidly by electron microscopic examination of pustular fluid or scabs. However, all orthopox viruses exhibit identical brick-shaped virions by electron microscopy. However, if particles with the characteristic morphology of herpes viruses are seen this will eliminate smallpox and other orthopox virus infections.
Definitive laboratory identification of variola virus involves growing the virus on chorioallantoic membrane (part of a chicken embryo) and examining the resulting pock lesions under defined temperature conditions. Strains may be characterized by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis. Serologic tests and enzyme linked immunosorbent assays (ELISA), which measure variola virus-specific immunoglobulin and antigen have also been developed to assist in the diagnosis of infection.
Chickenpox was commonly confused with smallpox in the immediate post-eradication era. Chickenpox and smallpox can be distinguished by several methods. Unlike smallpox, chickenpox does not usually affect the palms and soles. Additionally, chickenpox pustules are of varying size due to variations in the timing of pustule eruption: smallpox pustules are all very nearly the same size since the viral effect progresses more uniformly. A variety of laboratory methods are available for detecting chickenpox in evaluation of suspected smallpox cases.
2.6. PREVENTION AND TREATMENT:
There is no proven treatment for smallpox disease, but some antiviral drugs may help treat it or prevent it from getting worse. There also is a vaccine to protect people from smallpox. If there were a smallpox outbreak, health officials would use the smallpox vaccine to control it.
2.6.1. SMALLPOX VACCINE:
Before contact with the virus, the vaccine can protect you from getting sick.
Within 3 days of being exposed to the virus, the vaccine might protect you from getting the disease. If you still get the disease, you might get much less sick than an unvaccinated person would.
Within 4 to 7 days of being exposed to the virus, the vaccine likely gives you some protection from the disease. If you still get the disease, you might not get as sick as an unvaccinated person would.
Once an individual have developed the smallpox rash, the vaccine will not protect him. Currently, the smallpox vaccine is not available to the general public because smallpox has been eradicated, and the virus no longer exists in nature.
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