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Why Do We Fall ILL

Chapter: Why do We Fall ILL


Cell, which is defined as the basic structural and functional unit of life is made up of a variety of organic substances like proteins, carbohydrates, fats or lipids. . Living cell is an active place where some or the other activity is always happening.  Cells keep moving from one place to another. Even in cells that do not show any movement, there is repair going on and new cells are being made. Cluster of cells form tissues and these tissues are organized into specialized organs for performing various activities – for example- the heart beats, the lungs breathe, the kidney filters urine, the brain thinks. All these activities are interconnected. For all these interconnected activities, energy and raw materials are to be provided from outside the body. In other words, food is necessary for the proper functioning of cells and tissues. Anything that prevents proper functioning of cells and tissues will lead to lack of proper activity of the body.

Health and its Failure:

Significance of Health:

All of us like to remain fit and healthy. All of us know about the drawback of eating fast food and sedentary lifestyle. We often see people jogging or going for walks, practicing yoga or surya namaskar, early in the morning, before the start of the hectic day. Filtered and boiled water is preferred even in villages. We frequently hear words such as healthy habits, healthy diet and healthy lifestyle or the proverb “Health is wealth”. According to the World Health Organization (WHO), “Health is a state of complete physical, mental, social well-being of a person and not just the absence of diseases.”

Personal and Community issues (both matter for health):

Good health of an individual is the combined effort of the individual, the community and the society in which he or she lives and his or her physical environment.

Health means a state of physical, mental and social well-being, so it cannot be something that each one of us can achieve entirely on our own. The health of all organisms will depend on their surroundings, which includes their physical environment. But even more importantly, human beings live in societies.  Therefore, the environment is an important factor controlling an individual’s health. All of us live in villages, towns or cities. In such places, even our physical environment is decided by our social environment.

What would happen if no agency is ensuring that garbage is collected and disposed? What would happen if no one takes responsibility for clearing the drains and ensuring that water doesn’t collect in the streets or open spaces?

If there is a great deal of garbage strewn in our streets or if there is poor drainage system, the possibility of poor health increases. Therefore, keeping public places clean is important for individual health. We need food for being healthy and food has to be earned by doing work. For this, the opportunity to do work must be available. Therefore, Good economic conditions and jobs are also needed for individual health.

Distinction between Disease-free and Healthy:

The word disease means being uncomfortable. We talk of disease when we find a specific cause for discomfort. It is possible to be in poor health without actually suffering from a particular disease. Simply not having a disease doesn’t mean that the individual is healthy. ‘Good health’ for a singer may mean being able to sing without any disturbance in the voice. On the other hand, good health for an athlete may be being able to stretch his body without any problem. We can be said to have a poor health condition without knowing the cause of identifiable disease. This is the reason why when we think about health, societies and communities come into our mind. On the other hand, when we think about diseases, we think about individual sufferers.

Disease and its cause:

Disease is a condition of the body in which the vital functions are disturbed physiologically or psychologically. Specific symptoms and signs are associated with each disease.

The point of entry of the pathogen and its target tissue in the body may not be same. Example: Hepatitis virus enters through mouth and produces disease in the liver. Polio virus enters through mouth and affects the nervous system.

Signs and Symptoms of the Disease:

Symptoms of the diseases are the changes in our body that makes one feel sick or unwell. It is a feeling that is noticed by the patient indicating the presence of a sign of abnormality. It doesn’t pinpoint what the disease is. Example: headache may be the result of examination stress, an eye defect or tumor or a symptom of a many other diseases. Symptoms cannot be verified or measured; they are subjective to a particular patient. Example: Aches and pain, itching, cough, cold, etc.

Signs of a disease are what the medical practitioners look for on the basis of the symptoms. Signs give definite indications of the presence of a particular disease. The symptoms of different diseases may be the same but signs of different diseases are different. Signs of a disease can be verified or measured by a doctor. Hence, they are objective. Example: Blood pressure, Pulse rate, etc. The symptoms depend upon the target of pathogens in the human body. Example: when liver is the target, there is jaundice; when lungs are the target, the symptoms are cough and breathlessness. In addition to these specific effects, there can be other common effects or symptoms. Some of the effects are due to the body’s immune system, which fights off the disease-producing microbes. Because of infections, the immune system is activated and sends many white blood cells to the affected tissues to kill the microbes. This causes inflammation that leads to usual effects like swelling and pain and fever. To confirm the disease, a doctor carries out confirmatory tests like the blood test, urine, stool or even an x-ray.

Types of Diseases:

Diseases can be broadly classified in two different ways:

1. Types based on the time for which the disease lasts:

a. Chronic Diseases: Diseases that last for a long time, some times, even a lifetime. For example ; Diabetes and Tuberculosis.

b. Acute Diseases: Diseases that last for a shorter duration. As it gets cured fast, it doesn’t get time to cause major damage to the general health of the person. Example: Common cold.

2. Types based on the cause of the disease:

a. Diseases caused due to infectious agent or pathogen is called Communicable or Infectious disease. They are caused due to microbes like bacteria, fungi, virus, protozoa, etc. These diseases spread quickly and widely where, good community health is not maintained.  Examples are: Influenza, Amoebic dysentery.

b. Diseases, which are caused due to internal non-infectious reasons are called Non-Communicable or Non-Infectious disease. Such a disease is restricted to the person who is affected. Example: Genetic abnormalities, Wearing out of tissues e.g. - Arthritis, Deficiency disease e.g. - Night blindness and Degenerative diseases.

Chronic Diseases and Poor Health:

Acute and chronic diseases have different effects on our health. Any disease that causes poor functioning of some part of the body will affect our general health also. This is because each and every function is necessary to maintain general health. However, an acute disease, from which we recover soon, will not have time to cause any adverse effects on our general health unlike a chronic disease. Example: If we get infected with a chronic disease such as tuberculosis of the lungs, then being ill for a long time makes us lose weight and feel tired all the time.

Infectious and Non-infectious causes of Diseases:

When we think about a disease, it is important for us to keep public health and community health in mind. The immediate causes of the disease belong to two distinct groups. One group that causes diseases are the infectious agents that are mostly microbes and the other group is non-infectious agents. For example; high blood pressure is caused by excessive weight and lack of exercise and the other example is cancers, which are caused by genetic abnormalities. Diseases that are caused by microbes are called as infectious diseases. Diseases caused by microbes are said to be communicable, i.e. they spread from person to person in the community.


Infectious Agents: Microorganisms that cause diseases are viruses, fungi and protozoans. Some of the common examples are as follows- common cold, influenza, dengue fever and AIDS are caused by viruses. Bacteria cause diseases like typhoid, cholera, anthrax etc. Most of the skin infections are caused by fungi. Some familiar diseases like malaria and kala-azar are caused by the protozoans. Apart from these microorganisms, multicellular organisms like worms of different types also cause some of the diseases. Most of the intestinal infections and diseases like elephantiasis are caused by some special worms. Members of the groups like virus and bacteria have many characters including the biological characters in common. For example, all the members of the virus group live inside the host, whereas members of bacterial family do not. Taxonomically, all members of the bacterial family are closely related to each other than with the members of the virus family. Therefore, we can say that, when a drug blocks its activity, one of the members in the bacterial group is found to be effective against many other members of this group but the same drug may not be effective against viruses. For example antibiotics like penicillin are effective against bacteria but not against virus. Even in the cases where we get a bacterial infection along with a viral infection, we find the antibiotics working only against bacterial part of the infection but not against a viral infection.

Means of spread: An infectious disease spreads through air, water and food or by vectors (insects and animals) and through sexual contact. Diseases that are transmitted through air spread easily. This occurs through the little droplets expelled by an infected person when sneezed or coughed. Someone nearby can breathe in these droplets, and microbes get entry in to his or her body. Examples of such air-borne diseases are tuberculosis, Pneumonia, Swine Flu, etc. We live in an environment along with other living beings apart from us. It is inevitable that many diseases are transmitted to us by them. These animals are thus the intermediaries and are called vectors. The most common vector we all know is the mosquito. The female anopheles mosquito needs nutritious food in the form of blood in order to lay eggs. While sucking the blood, they infect the person with germs present in their body thus spreading malaria in healthy humans.

Diseases are also spread through water, for example if the excreta of a person suffering with cholera are mixed with the drinking water used by people living around ,then we can observe the disease spreading. The microorganism that causes cholera will enter into the new host through this water. Therefore, it is very important to maintain hygiene when it comes to drinking water and ensure safety while supplying it to public. Sexual contact is one of the closest means of keeping two people physically very close to each other. Diseases like AIDS and syphilis are spread through sexual contact. But we also have to keep in mind that sexually transmitted diseases are not spread through casual physical contact like handshaking or hugging or by any other casual means of contact. AIDS virus can spread from mother to her baby through breast feeding or during pregnancy.

Organ specific and Tissue specific manifestations: The disease causing microorganisms can enter body through different ways. Since the body is large compared to the microbes, there are many possible places, organs or tissues where the microbes could go. Different species of microbes use different routes for their entry into the body. If they enter from air via the nose, they are most likely to attack lungs. For example; tuberculosis. If the bacteria enter through mouth, it stays in the gut lining, causing diseases like typhoid. Sometimes the microbes entering through mouth could go to the liver and cause jaundice. Viral infection like HIV enters the body via the sexual organs and they spread through the entire body to lymph nodes. The signs and symptoms of the disease will depend on the tissue or organ attacked by the microbe. For example; if the target organ is lungs, then the symptoms would be cough and cold and if the target organ is liver, it could be jaundice. In addition to these issues, specific effects could also be there. Most of these common effects are due to  the response of the immune system to any infection. When any micro organism enters the body, the immune system responds by producing an effect like inflammation which will later result in fever. These effects are common to any microorganism. Therefore, they are called as common effects. It is very important to note that the severity of the disease depends on the number of microbes in the body.

Principles of Treatment:

There are two different ways to treat an infectious disease. One way is to reduce the effects of the disease and the other way is to kill the causes of the disease. By reducing the symptoms of the disease, we can reduce the effects of the disease too. For example, when we take medicines for fever, the medicines will bring down the temperature along with a decrease in the pain. But we cannot kill the microbe causing the disease, by using medicines for reducing the symptoms or signs of the disease. In order to cure the disease, we need to kill the microbes.

How do we kill microbes?

We can kill the microbes by using an appropriate medicine that could kill them. Microbes are basically classified as – viruses, bacteria, fungi and protozoa. The biochemical life process of organisms in one group varies with the organisms of the other group. We have to use a drug that can block these pathways as these pathways are the means for the synthesis of new substances. For example, we can use an antibiotic like penicillin to kill bacteria. The antibiotics kill the bacteria by blocking the cell wall synthesis pathway. Similarly, there are drugs for protozoa and fungi also. But making an anti viral medicine is very difficult since viruses enter our cells and use our cellular machinery for their life processes.

Principles of Prevention:

There are two different ways to prevent a disease. One is the general way and the other is specific to each disease. The general ways of preventing a disease include preventing ourselves from exposure to microbes. We can prevent our body from the exposure to microbes by living in places that are not over crowded, by drinking treated water, by maintaining a clean and healthy environment. Public hygiene is a basic factor for preventing infectious diseases. In addition to maintaining a good and healthy environment, our immune system is also one of the general ways to prevent infectious diseases. Our immune system is specialized with some type of cells and organs that can fight microbes. The cells in our immune system get activated and start fighting once any infectious agent enters our body. The functioning of the immune system will not be good if proper and sufficient amount of food is not available. Hence, proper availability of food is the second basic principle for the prevention of diseases. Specific way to prevent a disease is a peculiar property of our immune system that fights against microbes. For example, diseases like small pox are no longer seen today but in earlier days, this was the most dreadfully spreading disease. There were a group of people who suffered from small pox once and survived it, they did not get this disease second time. It was because of their immune system. Our immune system has a memory i.e. it recognizes the microbes it attacks for the first time and when the same microbe attacks again , it responds very quickly as it remembers the microbe. In recent times, we have vaccines to prevent certain diseases. Diseases like polio have been completely eradicated because of such vaccines.