Why Do We Fall Ill - Class 9 Biology - Extra Questions

(1) Maintaining hygienic conditions.
(2) Awareness about the disease and causal organism.
(3) Balanced diet.
(4) Regular medical check up.

There are two ways to treat an infectious (communicable) disease. These are:
(i) To reduce the effects of the disease : It can be done by providing symptomatic treatment. We can provide treatment that will reduce the symptoms. For instance, we can take medicines that bring down fever, reduce pain or loose motions. We can also have bed rest to conserve our energy. These steps will enable us to focus on healing. However, such a symptom-directed treatment by itself is not sufficient as it will not remove the disease-causing microbes from the body. To cure the disease, we need to kill the microbes.
(ii) To kill the cause of the disease, i.e., pathogens : The most common method to kill disease-causing microbes is to use medicines that  kill microbes. The disease-causing microbes are classified into different groups such as viruses, bacteria, fungi and protozoans. Each of these groups of microbes have some essential biochemical life processes which are peculiar to that group and not shared with the other groups. Our cells have different pathways than the ones used by these microbe groups. Therefore, we find a drug that blocks; for example, the bacterial biochemical path way without affecting our own. This is what is achieved by antibiotics. Similarly, there are drugs that kill protozoans, e.g., malarial parasite.

A vaccine is a biological preparation that provides active acquired immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism or the attenuated pathogen.

A generic drug is a medication created to be the same as an already marketed brand-name drug in dosage form, safety, strength, route of administration, quality, performance characteristics, and intended use. These similarities help to demonstrate bioequivalence, which means that a generic medicine works in the same way and provides the same clinical benefit as its brand-name version. In other words, you can take a generic medicine as an equal substitute for its brand-name counterpart.

Rabies is caused by a virus that affects the central nervous system. Dogs are the most frequently reported rabid domestic animals. The bite of such dogs can spread rabies.

• It is more difficult to make antiviral medicines than making antibiotics because viruses have few biochemical mechanisms of their own.
• They enter the host cells and use their machinery for their life processes. 
• So, antiviral medicines will work against the host body. 
• Antibiotics block bacterial synthesis pathways without affecting the body because bacteria use their own metabolic pathway machinery 
• so, it will not affect the host body.

KALA AZAR - Leishmania

Common cold, Tuberculosis

Cholera

$$\textbf{Concept applied:}$$ Infectious diseases can be prevented by following some basic principles.

(1) General ways of prevention of infectious diseases

(i) Sanitation: Garbage heaps, polluted water, foods exposed to dust and flies are the chief sources of disease-causing organisms. Practicing good hygiene and sanitation can prevent the spread of diseases.

(ii) Eradication of vectors: Vector-borne infections can be prevented by providing clean environments. The breeding places of vectors should be destroyed and adult vectors killed by suitable methods.

(iii) Sterilization: The patient’s surroundings and articles of use should be sterilized. Soap, phenyl, dettol, and antiseptic lotions may be used wherever necessary.

(iv) Isolation: The person suffering from an infectious disease should be kept in isolation so that others do not catch the infection from him or her.

(v) Awareness: People should be educated and made aware of infectious diseases so that they may protect themselves against such infections.

(vi) Proper and sufficient food: Availability of proper (nutritious) and sufficient food to everyone will make people healthy to resist infections.

(2) Specific ways of prevention of infectious diseases

(i) Getting healthy people vaccinated is the specific way of prevention of infectious diseases. 

(ii) A vaccine is the preparation of killed or inactive disease-causing microbe that is injected into the body of a healthy person. 

(iii) The body’s immune system fights off the injected disease-causing agent by producing antibodies. 

(iv) Thus, the body prepares itself to fight the infection without actually getting the infection.

(v) This is the basis of the principle of immunization.

The severity of disease manifestation is determined by several factors. One of the most important factors is the duration of the disease. Some diseases last only for a few days. Eg: Common cold. They are referred to as acute infections. Others may even last for a life time referred to as chronic infection. Eg: Elephantiasis.

There are two basic ways of preventing a disease:
1. General way of preventing an infectious disease is preventing exposure to the pathogens. There are several means by which exposure can be prevented and it depends on the type of microbes.
2. Specific way of preventing a disease is by immunization. Several vaccines have been developed prevent diseases. Eg: MMR, polio, tetanus.

The place of manifestation of disease-causing microbes in the body depends on the entry route of the microbes. For example, the microbes of tuberculosis enter through the nose, so, they infect the lungs. 

(i) Helicobacter pylori causes peptic ulcers
(ii) It was first discovered by two Australian doctors Marshall and Warren in the year 1982.

Fits or unconsciousness targets the Brain.

Boiling and filtration are methods of purifying water which makes it suitable for consumption. Drinking boiled and filtered water can help in prevention of water borne diseases such as typhoid, cholera, etc. Most of the water borne diseases are transmitted through the consumption of contaminated water in some or the other form. 

It is not necessary that the pathogen may affect an organ or tissue depending upon the point of entry.
The statement can be explained by the following example of an HIV virus which is the causative agent for AIDS.
The virus entering through blood or during sexual contact affects the entire immune system by capturing the host machinery thereby leading to various other kinds of infections.

a. Yes, availability of proper and sufficient food would prevent infectious diseases because proper food intake will boost the functioning of the immune system. 
Without proper food supply and nourishment, the immune system will not be able to function properly which may give a door to various diseases.

b. Yes, the general ways of preventing infection mostly relate to preventing exposure because of the following:
i.  For air borne microbes, we can prevent the exposure by staying away from crowded places.
ii. We can prevent exposure to water borne microbes by using safe drinking water
iii. For vector borne, a clean environment stops the exposure to the microbes. 

Antibiotic is a chemical secreted by microorganisms (bacteria or fungi) that kills or hinders the growth of some kinds of bacteria. Examples. Penicillin and streptomycin.

Vaccination is the technique to develop immunity in individuals against specific diseases without infection. Edward Jenner first conceived the idea of vaccination.

(i) Helicobacter pylori - is the bacterium that causes peptic ulcers.
(ii) Marshall and Warren - discovered the pathogen of peptic ulcers for the first time.

The fluid inside and outside cells is not pure water; it contains dissolved substances such as salts and sugars. To prevent cells from shriveling or swelling because of osmosis, it is best to give a patient an intravenous solution with a concentration of dissolved substances that is close to the concentration of dissolved substances in the body's fluids.

A cold is caused by a viral infection. When viruses enter the host body, they take a definite time period, seven days in this case, to complete the life cycle a patient is cured only after the expiry of the period. Medicines taken during this period do not kill the virus, they only prevent secondary infections which may develop due to viral infection.

A generic drug is a pharmaceutical drug which is equivalent to a brand name drug product in its dosage, strength, route of administration, quality, performance, and intended use but does not carry the brand name. The generic drug may differ from the original in non-essential characteristics such as color taste and packaging.