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Chapter Contents Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph. 011-47623456 Common Diseases in Humans Immunity AIDS Cancer Drugs and Alcohol Abuse Health Health does not simply mean ‘absence of disease’ or ‘physical fitness’. It is defined as a state of complete physical, mental and social well being. Health can be affected by (i) Genetic disorders : Deficiencies with which a child is born or deficiencies/defects which the child inherits from parents birth. (ii) Infections, (iii) Life style including food and water (balanced diet) we take, rest and exercise (yoga) we give to our bodies or habits that we have or lack. Note : Hippocrates is called father of medicine. William Harvey disproved the ‘good humor’ hypothesis. Disease When the functioning of one or more organs or systems of the body is adversely affected, characterised by various signs and symptoms, we say, that we are not healthy, i.e., we have a disease. Disease can be broadly classified into two categories: (A) Congenital Diseases : These diseases occur at birth and may result from metabolic disorders or defects in development. (B) Acquired diseases : These diseases develop after birth and can be divided into two main categories : (i) Infectious diseases/Communicable diseases : Diseases which are easily transmitted from one person to another are called infectious diseases. Infectious diseases are very common and some of the infectious diseases like AIDS are fatal. (ii) Non-infectious diseases/Non-communicable diseases : These diseases are not spread to other persons. Among non-infectious diseases, cancer is the major cause of death. Chapter 16 Human Health and Disease
2 Human Health and Disease NEET Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph. 011-47623456 Pathogen A wide range of organisms could cause diseases in man. Such disease causing organisms are called pathogens e.g., bacteria, viruses, fungi, protozoans, helminths etc. Most parasites are therefore pathogens as they cause harm to the host body by living in or on them. The pathogens can enter our body by various means, multiply and interfere with normal vital activities, resulting in morphological and functional damage. Pathogens have to adapt to life within the environment of the host. For example, the pathogens that enter the gut must know a way of surviving in the stomach at low pH and resisting the various digestive enzymes. COMMON DISEASES IN HUMANS A. Bacterial Diseases (i) Typhoid: (Enteric fever) Pathogen: Salmonella typhi (A Gram negative bacterium) Mode of transmission: These pathogens generally enter the small intestine through contaminated food & water and migrate to other organs through blood. Symptoms: Sustained high fever (39° to 40°C), weakness, stomach pain, constipation, headache, and loss of appetite are some of the common symptoms of this disease. Intestinal perforation and death may occur in severe cases. Test: Typhoid fever could be confirmed by Widal test. Note : Mary Mallon was carrier of typhoid who spread the disease through the food she prepared. Hence was nicknamed, Typhoid Mary. (ii) Pneumonia: Pathogen: Bacteria like Streptococcus pneumoniae and Haemophilus influenzae. Mode of transmission: A healthy person acquires the infection by inhaling the droplets / aerosols released by an infected person or even by sharing glasses and utensils with an infected person. Symptoms: In pneumonia, infection occurs in alveoli of the lungs. As a result of the infection, the alveoli gets filled with fluid leading to severe problems in respiration. The symptoms of pneumonia are fever, chills, cough and headache. In severe cases, the lips and finger nails may turn gray to bluish in colour. (iii) Plague/Bubonic plague: (Black death) Pathogen: Yersinia pestis Mode of infection: It is primarily a disease of rodents but can accidently affect man. It spreads from rat to rat through rat flea (Xenopsylla). But when the infected rats die, the fleas leave their body and could bite man injecting plague pathogens into his blood. Symptoms: It is characterised by high fever and a bubo (lump) in the groin or the armpit. Red patches appear on skin which turn black and ultimately lead to death (black death). Wayson–stain test helps to detect plague. (iv) Tuberculosis (TB) : It is also called Koch’s disease. It is caused by Mycobacterium tuberculosis. The bacteria damages the tissues and releases a toxin named tuberculin which produces the disease. It affects the lungs, lymph nodes, bones and joints. Incubation period is quite variable. Symptoms of pulmonary (lungs) tuberculosis are fever, cough, sputum containing blood, pain in the chest and loss of weight, excessive fatigue, loss of appetite, rise of temperature in the evening, hoarseness of throat, night sweating and rapid pulse. BCG vaccine gives considerable protection against tuberculosis. TB can be detected using Mantoux test.
NEET Human Health and Disease 3 Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph. 011-47623456 (v) Leprosy (Hansen’s Disease) : This disease is caused by Mycobacterium leprae, which was discovered by Hansen. Symptoms of leprosy include appearance of light coloured patches on the skin, thickening of the nerves, partial or total loss of sensation in the affected parts of the body. These are accompanied by fever, pain, ulcers and skin eruptions. Deformities of toes and fingers may also develop. The bacilli leave the body in nasal discharge, from the throat during coughing, sneezing or speaking and through broken skin lesions. The patient is treated with DDS (diamino diphenyl sulphone). (vi) Cholera : This is an acute infectious disease caused by Vibrio cholerae. These may get into a healthy person with contaminated food and water. The patient starts passing stools frequently, which are white like rice-water and vomits repeatedly. Since, a large quantity of fluid and salts are rapidly lost through stools and vomit, therefore, the most important treatment is to replace the lost fluid and salts equally by oral rehydration therapy. (vii) Diphtheria : This disease is caused by Corynebacterium diphtheriae usually affecting children upto five years of age. It may start with sore throat, chills with mild fever, sometimes vomiting and headache. Throat or tonsils show a grey membrane which may spread down and cause hoarseness and difficulty in breathing. The most important preventive measure-against this disease is that all babies should be immunised within the first six weeks of birth using DPT vaccine. (viii) Tetanus (Lock Jaw) : It is caused by Clostridium tetani which produces a neurotoxin tetanospasmin which acts at neuromuscular junction. The first indications of this disease are irritability and restlessness, stiffness of neck and difficulty in chewing and swallowing. Subsequently, spasms of muscles of the jaw and face take place and thus “Lock Jaw” occurs. There is severe pain. It is often a fatal disease. The toxin mainly affects ‘voluntary muscles’. Tetanus organisms live in the intestine of horses and other animals without doing any harm. Anti tetanus serum (ATS) injection should be administered in case of an injury. B. Viral Diseases (i) Common cold/Rhinitis : Pathogen: Rhino virus. Mode of infection: It is one of the most infectious human diseases, transmitted through inhalation of droplets resulting from cough or sneeze of an infected person, either inhaled directly or transmitted through contaminated objects such as pens, books, cups, door knobs, computer keyboard etc. (fomite borne). Symptoms: Rhino virus infects the nose and respiratory passage but not the lungs. (Upper Respiratory tract infection) It is characterised by nasal congestion and discharge, sore throat, hoarseness, cough, headache, fatigue, etc., which usually lasts for 3-7 days. (ii) Influenza : It is commonly known as “Flu” and is highly infectious. The disease is caused by various types of influenza viruses (e.g., Myxovirus influenzae). It causes fever and pain all over the body and affects the nose, throat and air passages as in common cold. It starts with fever, headache, sore throat, cold with sneezing and pain all over the body with restlessness. In neglected cases, complications like pneumonia, bronchitis and ear infections may develop. (iii) Small Pox : This disease is caused by a small pox virus named Variola virus (ds DNA virus). The virus is present in the oral and nasal discharges of the patients and is ejected during the acts of coughing, sneezing, fomites etc., and infects the healthy people. It is highly infectious disease starting with high fever, chill, backache and headache, followed by appearance of rash on the third day of illness. The rash appears first on the face followed by rest of the body. It is more on the face and limbs and less on the trunk. The rash starts as a small reddish spot which change into papules. These in turn change into small vesicles containing clear fluid. Vesicles change into pustules. Finally, a scab is formed and it falls off by the third week. These scabs leave deep pits or scars known as pock marks. Many children may become blind and develop discharge from the ear. Vaccination against small pox is one of the best preventive remedies available today. This was discovered by Edward Jenner in 1798. Small-pox has been eradicated from the world.
4 Human Health and Disease NEET Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph. 011-47623456 (iv) Chicken Pox : This disease is caused by a virus of chicken-pox named Varicella zoster (dsDNA virus) which is passed out in the discharges of the respiratory tract of an infected person directly as droplets or through contaminated articles used by the patient. It is a mild but highly infectious disease causing slight fever and a rash which undergoes changes into Chicken-pox vesicles, pustules and finally a dark brown scab which falls off leaving no scar unlike smallpox. The rash comes out in crops and with each fresh crop, there may be slight fever again. The rash first appears on the trunk and there are more lesions on the trunk than on the face and limbs. Vaccination against chicken-pox is now available. The most common late complication of chicken-pox is shingles caused by reactivation of Varicella zoster. (v) Measles (Rubeola Disease) : It is caused by Rubeola virus (RNA virus) which is passed out in the secretions of nose and throat of the infected persons as droplets or in articles soiled by these secretions. The disease starts with catarrh of the nose and throat, and fever. It is a highly infectious disease causing, inflammation of the air passages and a rash all over the body. The rash which is slightly pinkish in colour first appears on the back of the ear and face, and spreads downwards on the body. It attacks especially the children below the age of 5 years and those who have escaped may be attacked in the later years of life. The eyes are red and watery, and the face is flushed. (vi) Mumps (Infectious Parotitis) : It is an infectious disease causing fever, difficulty in opening the mouth and painful swelling of the parotid glands which lie just below the lobe of the ears. It is caused by Paramyxovirus (RNA virus), which comes out in the saliva of the infected person. The A boy with mumps patient should take complete bed rest till the swelling subsides in order to avoid complications. Usually, there are no complications, but in some cases there may be pain and swelling of the testes (orchitis) or pain in the abdomen. (vii) Rabies (Hydrophobia) : It is caused by a virus called Rhabdo virus. It is mostly introduced in humans by the bite of rabid (mad) dogs. It can also be injected by the bite of jackals, wolves, cats etc., Incubation period is from 10 days to one year. Fear of water is the most important characteristic symptom of this disease. Other symptoms are excess salivation, severe headache, high fever, alternating periods of excitement and depression, inability to swallow food and even fluids due to choked throat. The virus destroys the brain and spinal cord. Rabies is 100% fatal. There should be compulsory immunisation of dog and cat population. (viii) Poliomyelitis : This disease was called infantile paralysis. But it is now known that the disease may occur at any age. This disease spreads mainly through intestinal discharges. It may also spread through contaminated food or drink and by flies or other insects that may contaminate food or drink. Polio virus (ss RNA) usually enters the body via alimentary canal where it multiplies and reaches the nervous system (spinal cord) through the blood stream. Its incubation period is 7-14 days. It produces inflammation of the nervous system. The earliest sign of this disease is involvement of the central nervous system causing inability to bend the head forward. Stiffness of the neck is an important sign. Paralysis starts following the weakness of particular skeletal muscles. The attack of paralysis begins with high fever, headache, chills, pain all over the body. If muscles of larynx and pharynx are involved it proves fatal. Within two to three days the paralysis reaches its maximum. There is no sure cure for polio. The patient should be kept isolated. He should be given complete rest. An adequate arrangement for proper disposal of urine and faeces of the patient must be provided because they contain polio virus. Overcrowding of children in schools, playgrounds and cinema should be avoided. Polio is preventable. Polio vaccine is safe and effective. Now-a-days multiple vaccines are used against polio, diphtheria, whooping cough and tetanus simultaneously.