Chapter 13-Why Do We Fall Ill?

Health and its Failure

THE SIGNIFICANCE OF ‘HEALTH’

==Being healthy means having enough physical, mental, and social capacity to carry out daily activities.==

PERSONAL AND COMMUNITY ISSUES BOTH MATTER FOR HEALTH

• Every organism's health will be influenced by its environment or surrounds. The physical environment is a part of the environment. In a cyclone, for instance, there are numerous ways that health is at risk.
• We reside in towns, cities, or rural areas. In these settings, even our physical environment are influenced by our social surroundings.
• The likelihood of poor health rises if there is a lot of trash dumped in our streets or if there is stagnant open drainwater near our homes.As a result, maintaining a clean environment is crucial for personal health.

DISTINCTIONS BETWEEN ‘HEALTHY’ AND ‘DISEASE-FREE’

• Disease, in other words, literally means being uncomfortable.We can easily see that it is possible to be in poor health without actually suffering from a particular disease.
• Simply not being diseased is not the same as being healthy.we can be in poor health without there being a simple cause in the form of an identifiable disease..
• This is the reason why, when we think about health, we think about societies and communities. On the other hand, when we think about disease, we think about individual sufferers.’

Disease and Its Causes

WHAT DOES DISEASE LOOK LIKE?

• When there is a disease, either the functioning of one or more systems of the body will change for the worse.
• These changes give rise to symptoms and signs of disease.
• Symptoms of disease are the things we feel as being ‘wrong’. So we have a headache, we have cough,we have a wound with pus; these are all symptoms.
• Signs of disease are what physicians will look for on the basis of the symptoms. Signs will give a little more definite indication of the presence of a particular disease.
• Physicians will also get laboratory tests done to pinpoint the disease further.

ACUTE AND CHRONIC DISEASES

• Different disease symptoms will occur depending on a variety of factors.
• Acute diseases are those that only last for incredibly short periods of time.We all know from experience that the common cold lasts only a few days.
• Chronic diseases are conditions that can persist for a very long time, even a lifetime.. An example is the infection causing elephantiasis, which is very common in some parts of India.

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 health. This is because all functions of the body are necessary for being healthy.
• An acute illness, which ends quickly, won't have time to have a significant impact on overall health, whereas a chronic illness will.o. As an example,cough and cold, which all of us have from time to time. Most of us get better and become well within a week or so. And there are no lasting effects on our health
• If we get infected with a chronic disease such as tuberculosis of the lungs, then being ill over the years does make us lose weight and feel tired all the time.
• Chronic diseases therefore, have very drastic long-term effects on people’s health as compared to acute diseases.

Causes of Diseases

• There are immediate and contributory causes for every disease. Additionally, most diseases have multiple causes rather than just one.

INFECTIOUS AND NON-INFECTIOUS CAUSES

The immediate causes of disease as belonging to two distinct types-

• One group of causes is the infectious agents, mostly microbes or micro-organisms. Diseases where microbes are the immediate causes are called infectious diseases. This is because the microbes can spread in the community, and the diseases they cause will spread with them.
• On the other hand, some illnesses are not brought on by infectious agents. Although their sources can vary, they are not external factors like microorganisms that can spread around the neighbourhood. Instead, internal, non-infectious factors predominate. For instance, genetic anomalies can result in cancer. Both being overweight and not exercising enough might raise blood pressure. Diabetes is also not infectious.

Infectious Diseases

• ==Diseases where microbes are the immediate causes are called infectious diseases.==
• This is because the microbes can spread in the community, and the diseases they cause will spread with them.

INFECTIOUS AGENTS

• Disease-causing organisms can be found in a wide variety of these classification categories.

• They include viruses, bacteria, fungus, single-celled animals, and protozoans, among other types of organisms.

• Multicellular creatures like various types of worms can also cause some diseases

• Common examples of diseases caused by viruses are the common cold, influenza, dengue fever and AIDS. Diseases like typhoid fever, cholera, tuberculosis and anthrax are caused by bacteria.

• Many common skin infections are caused by different kinds of fungi.

• Protozoan microbes cause many familiar diseases, such as malaria and kalaazar.

• All of us have also come across intestinal worm infections, as well as diseases like elephantiasis caused by diffferent species of worms.

ANTIBIOTICS

• Antibiotics frequently obstruct vital bacterial metabolic pathways.
• For instance, many bacteria build a cell wall to defend themselves.
• The bacterial cellwall-building mechanisms are inhibited by the antibiotic penicillin.
• As a result, the developing bacteria are unable to construct cell walls and quickly perish.
  Penicillin cannot have such an impact on human cells since they don't produce cell walls.
  Penicillin will have this effect on any bacterial cell-wall-producing mechanisms.
  Similar to how various antibiotics combat multiple bacterial species as opposed to only one.

MEANS OF SPREAD

Many microbial agents can commonly move from an affected person to someone else in a variety of ways. In other words, they can be ‘communicated’, and so are also called communicable diseases.

• These infectious bacteria have the ability to travel via the air. This happens as a result of the microscopic droplets that an infected individual coughs or sneezes release . These droplets can be inhaled by someone nearby, giving the bacteria a chance to establish a new infection. The common cold, coronavirus disease (COVID-19), pneumonia, and tuberculosis are a few examples of such illnesses that spread through the air.

• Diseases can also be spread through water. This occurs if the excreta from someone suffering from an infectious gut disease, such as cholera, get mixed with the drinking water used by people living nearby. The choleracausing microbes will enter a healthy person through the water they drink and cause disease in them. Such diseases are much more likely to spread in the absence of safe supplies of drinking water

• The sexual act is one of the closest physical contact two people can have with each other. Not surprisingly, there are microbial infections such as syphilis or AIDS that are transmitted by sexual contact from one partner to the other. However, such sexually transmitted diseases are not spread by casual physical contact. Casual physical contacts include handshakes or hugs or sports, like wrestling, or by any of the other ways in which we touch each other socially. Other than the sexual contact, the virus causing AIDS (HIV) can also spread through blood-to-blood contact with infected people or from an infected mother to her baby during pregnancy or through breast feeding. , in HIV infection, the virus goes to the immune system and damages its function. Thus, many of the effects of HIV-AIDS are because the body can no longer fight off the many minor infections that we face everyday. Instead, every small cold can become pneumonia.

It is inevitable that other animals will spread numerous diseases. Animals spread infectious substances from a sick person to a potential host. Thus, these creatures are the intermediaries and are referred to as vectors.

• Thus the intermediaries and are called vectors.
• The commonest vectors we all know are mosquitoes.
• In many species of mosquitoes, the females need highly nutritious food in the form of blood in order to be able to lay mature eggs.
• Mosquitoes feed on many warm-blooded animals, including us. In this way, they can transfer diseases from person to person

ORGAN-SPECIFIC AND TISSUESPECIFIC MANIFESTATIONS

• Microbes of various kinds appear to have evolved to target particular body parts.
• This selection is partially influenced by their site of entry.
• They are most likely to reach the lungs if they enter from the air through the nose.
  The microorganisms that cause tuberculosis exhibit this.
• They can remain in the stomach lining, much like the germs that cause typhoid, if they enter by the mouth.
• Alternatively, like viruses that cause jaundice, they may enter the liver.
• But this needn’t always be the case. An infection like HIV, that comes into the body via the sexual organs, will spread to lymph nodes all over the body.
• Malaria-causing microbes, entering through a mosquito bite, will go to the liver, and then to the red blood cells.

Virus causing Japanese encephalitis

• The virus causing Japanese encephalitis, or brain fever, will similarly enter through a mosquito bite.
• But it goes on to infect the brain.
• The signs and symptoms of a disease will thus depend on the tissue or organ which the microbe targets.
• If the lungs are the targets, then symptoms will be cough and breathlessness. If the liver is targeted, there will be jaundice.
• If the brain is the target, we will observe headaches, vomiting, fits or unconsciousness.
• We can imagine what the symptoms and signs of an infection will be if we know what the target tissue or organ is, and the functions that are carried out by this tissue or organ.

SWELLING OR FEVER IN A DISEASE

• In addition to these tissue-specific effects of infectious disease, there will be other common effects too. Most of these common effects depend on the fact that the body’s immune system is activated in response to infection.
• An active immune system recruits many cells to the affected tissue to kill off the disease-causing microbes.
• This recruitment process is called inflammation.
• As a part of this process, there are local effects such as swelling and pain, and general effects such as fever.

PRINCIPLES OF TREATMENT

• we can provide treatment that will reduce the symptoms. The symptoms are usually because of inflammation. For example, we can take medicines that bring down fever, reduce pain or loose motions. We can take bed rest so that we can conserve our energy. This will enable us to have more of it available to focus on healing.

• How do we kill microbes? One way is to use medicines that kill microbes. We have seen earlier that microbes can be classified into different categories. They are viruses, bacteria, fungi or protozoa. Each of these groups of organisms will have some essential biochemical life process which is peculiar to that group and not shared with the other groups. These processes may be pathways for the synthesis of new substances or respiration. These pathways will not be used by us either. For example, our cells may make new substances by a mechanism different from that used by bacteria. We have to find a drug that blocks the bacterial synthesis pathway without affecting our own. This is what is achieved by the antibiotics that we are all familiar with. Similarly, there are drugs that kill protozoa such as the malarial parasite.

• One reason why making anti-viral medicines is harder than making antibacterial medicines is that viruses have few biochemical mechanisms of their own. They enter our cells and use our machinery for their life processes. This means that there are relatively few virus-specific targets to aim at. Despite this limitation, there are now effective anti-viral drugs, for example, the drugs that keep HIV infection under control.

PRINCIPLES OF PREVENTION

• Prevention of disease is more desirable than its successful treatment.
• Infectious diseases can be prevented by public health hygiene measures that reduce exposure to infectious agents.
• Infectious diseases can also be prevented by using immunisation.
• Effective prevention of infectious diseases in the community requires that everyone should have access to public hygiene and immunisation.