These NCERT Solutions for Class 9 Science Chapter 13 Why Do We Fall Ill Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.
Why Do We Fall Ill NCERT Solutions for Class 9 Science Chapter 13
Class 9 Science Chapter 13 Why Do We Fall Ill InText Questions and Answers
State any two conditions essential for good health.
The two conditions essential for good health are:
- An individual must have better health facilities and more professionals to deal with health problems.
- All basic necessary conditions to prevent diseases must be present. For example, proper garbage collection and disposal, clearing of drains, supply of healthy drinking water, etc.
State any two conditions essential for being free of disease.
The two conditions essential for being free of diseases are:
- Personal hygiene and cleanliness are necessary to stay away from diseases.
- Individuals should take a balanced diet that contains carbohydrates, fats, proteins, vitamins, fibres, and proper quantity of water.
Are the answers to the above questions necessarily the same or different? Why?
No. The answers to the above questions may not necessarily be the same. This is because a disease free state is not the same as being healthy. Good health is the ability of an individual to realise his or her full potential. Individuals can have poor health without having any identifiable disease. Also, health is related to society and community, whereas having a disease is about an individual sick person. Hence, the conditions for good health and for being disease free can be same or even different.
List any three reasons why you would think that you are sick and ought to see a doctor. If only one of these symptoms were present, would you still go to the doctor? Why or why not?
Symptoms such as a headache, stomach pain, nausea, vomiting, fever, etc., make us feel that we are sick and must visit a doctor. These symptoms basically indicate that there might be a disease, but we cannot predict the kind of disease. Therefore, it becomes necessary to visit a doctor so that the disease can be identified and can be treated with proper medication.
However, if only one of these symptoms is present, we usually do not visit a doctor. This is because such symptoms do not have much effect on our general health and ability to work. However, if a person is experiencing these symptoms for quite sometime, then he needs to visit a doctor for proper treatment.
In which of the following case do you think the long-term effects on your health are likely to be most unpleasant?
- If you get jaundice,
- If you get lice,
- If you get acne.
Jaundice is a disease that can cause long-term effects on our health. It is a chronic disease that lasts for a long period of time. Jaundice does not spread rapidly, but it develops slowly over a period of time.
Why are we normally advised to take bland and nourishing food when we are sick?
We are normally advised to consume bland and nourishing food when we are sick so that we can get the nutrients and energy quickly to fight off the foreign disease-causing agents.
What are the different means by which infectious diseases are spread?
Diseases can be spread through various means such as air, water, sexual contact, blood, and vector.
- Certain disease-causing micro-organisms are expelled in air by coughing, sneezing, talking, etc. These micro-organisms can travel through dust particles or water droplets in air to reach other people. For example, tuberculosis, pneumonia, etc. spread through air.
- Sometimes causal micro-organisms get mixed with drinking water and spread water borne diseases. Cholera for example is waterborne disease.
- Sexual act between two people can lead to the transfer of diseases such as syphilis, gonorrhoea, AIDS, etc.
- Certain diseases such as AIDS can spread via blood-to-blood contact during blood transfusion or pregnancy.
- Certain diseases spread by animals called vectors. For example mosquitoes spread malaria.
What precautions can you take in your school to reduce the incidence of infectious diseases?
Precautions to reduce incidence of infectious diseases are:
- Stay away from the diseased person.
- Cover your mouth or nose while coughing or sneezing to prevent the spread of disease.
- Drink safe water.
- Keep the environment clean to prevent mosquitoes from breeding.
What is immunization?
Immunizations defined as protection of the body from communicable diseases by administration of some agent that mimics the microbe. This suspension of killed microbes that mimics the disease-causing microbes is known as vaccines.
What are the immunization programmes available at the nearest health centre in your locality? Which of these diseases are the major health problems in your area?
The immunization programmes available at the nearest health centre are DPT (Diphtheria, Pertusis, and Tetanus), polio vaccine, hepatitis B, MMR (Measles, Mumps, and Rubella), jaundice, typhoid, etc.
Of all these diseases, jaundice and typhoid are major health problems.
Class 9 Science Chapter 13 Why Do We Fall Ill Textbook Questions and Answers
How many times did you fall ill in the last one year? What were the illnesses?
(a) Think of one change you could-make in your habits in order to avoid any of /most of the above illnesses.
(b) Think of one change you would wish for in your surroundings in order to avoid any of/most of the above illnesses.
This varies from person to person. Some people fall ill several times in a year, while others do not fall ill at all. A person’s immune system and hygiene-related habits play a major role in determining the person’s health.
A doctor/nurse/health worker is exposed to more sick people than others in the community. Find out how she/he avoids getting sick herself/himself.
The following precautions must be taken by a doctor/ nurse/ health-worker:
- Wearing a mask when in contact with a diseased person.
- Keeping yourself covered while moving around an infected place.
- Drinking safe water.
- Eating healthy and nutritious food.
- Ensuring proper cleanliness and personal hygiene.
Conduct a survey in your neighbourhood to find out what the three most common diseases are. Suggest three steps that could be taken by your local authorities to bring down the incidence of these diseases.
Three most common diseases are:
Steps to be taken to bring down the incidence of these diseases are:
- Proper disposal of sewage.,
- Ensuring supply of safe drinking water.
- Providing a clean environment and preventing mosquitoes from breeding.
A baby is not able to tell her/his caretakers that she/he is sick. What would help us to find out
(a) that the baby is sick?
(b) what is the sickness?
(a) The baby is sick can be determined by his/ her behavioural changes such as constant crying of baby, improper intake of food, frequent mood changes, etc.
(b) The sickness is determined by symptoms or indications that can be seen in the baby. The symptoms include vomiting, fever, loose motion, paleness in the toe body, etc.
Under which of the following conditions is a person most likely to fall sick?
(a) when she is recovering from malaria.
(b) when she has recovered from malaria and is taking care of someone suffering from chickenpox.
(c) when she is on a four-day fast after recovering from malaria and is taking care of someone suffering from chickenpox.
(c) A person is more likely to fall sick when she is cm a four day fast after recovering from malaria and is taking care of someone who is suffering from chickenpox. This is because she is fasting during recovery, and her immune system is so weak that it is not able to protect its own body from any foreign infection. If she is taking care of someone suffering from chickenpox, then she has more chances of getting infected from chickenpox virus and will get sick again with this disease.
Under which of the following conditions are you most likely to fall sick?
(a) when you are taking examinations.
(b) when you have travelled by bus and train for today.
(c) when your friend is suffering from measles.
(c) You are more likely to fall sick when your friend is suffering from measles. This is because measles is highly contagious and can easily spread through respiration i.e., through air. Thus, if your friend is suffering from measles, stay away from him otherwise you might easily get infected with the disease.
Class 9 Science Chapter 13 Why Do We Fall Ill Additional Important Questions and Answers
Choose the correct option:
Which one of the following is not a viral disease?
Which one of the following is not a bacterial disease?
Which one of the following diseases is not transmitted by mosquitoes?
(a) Brain fever
Which one of the following disease is caused by bacteria?
Which one of the following diseases is caused by protozoans?
Which one of the following has a long-term effect on the health of an individual?
(a) Common cold
(c) Chewing tobacco
(c) Chewing tobacco
Which of the following can make you ill if you come in contact with an infected person?
(a) High blood pressure
(b) Genetic abnormalities
(d) Blood cancer
AIDS cannot be transmitted by
(a) sexual contact
(d) blood transfusion
Making anti-viral drugs is more difficult than making anti-bacterial medicines because
(a) viruses make use of host machinery
(b) viruses are on the borderline of living and non-living
(c) viruses have very few biochemical mechanisms of their own
(d) viruses have a protein coat
(c) viruses have very few biochemical mechanisms of their own
Which one of the following causes kala-azar?
If you live in a overcrowded and poorly ventilated house, it is possible that you may suffer from which of the following diseases
(c) Airborne diseases
(c) Airborne diseases
Which disease is not transmitted by mosquitoes?
(c) Brain fever or encephalitis
Which one of the following is not important for individual health?
(a) Living in clean space
(b) Good economic condition
(c) Social equality and harmony
(d) Living in a large and well furnished house
(d) Living in a large and well furnished house
Choose the wrong statement
(a) High blood pressure is caused by excessive weight and lack of exercise.
(b) Cancers can be caused by genetic abnormalities
(c) Peptic ulcers are caused by eating acidic food
(d) Acne in not caused by staphylococci
(c) Peptic ulcers are caused by eating acidic food
We should not allow mosquitoes to breed in our surroundings because they
(a) multiply very fast and cause pollution
(b) are vectors for many diseases
(c) bite and cause skin diseases
(d) are not important insects
(b) are vectors for many diseases
Very Short Answer Questions
Write the full form of AIDS.
AIDS stand for Acquired immunodeficiency syndrome.
Name the three diseases for which a child is vaccinated with DPT?
DPT is vaccine for diphtheria, whooping cough and tetanus.
Which body cells contribute to the immunity against the infection?
WBC, particularly the phagocytes and lymphocytes.
Which diseases are more fatal, acute or chronic? Why?
Acute diseases are more fatal than chronic because of their quick manifestations.
Give three examples of each the followings:
(a) Waterborne disease
(b) Airborne disease
(a) Typhoid, cholera and jaundice.
(b) Tuberculosis, influenza and common cold
(c) AIDS, syphilis and gonorrhea
Give three examples of each of the followings:
(a) Viral disease
(b) Bacterial diseases
(c) Protozoan diseases
Viral diseases: Chickenpox, polio and measles Bacterial disease: Typhoid, cholera and tuberculosis Protozoan diseases : Malaria, sleeping sickness and kala-azar
Give three examples of each of the followings:
(a) Disease transmitted by water
(b) Diseases transmitted by air
(c) Diseases transmitted by vector
(a) Cholera, typhoid and jaundice.
(b) Tuberculosis, meningitis and polio.
(c) Malaria, Sleeping sickness and dengue.
Name the nutrients which contribute to the body’s immunity.
Vitamins and minerals
Which disease you expect a person to suffer from if he joins an overcrowded place?
Which is the commonly found element in the most of antibiotics?
Short Answer Type Questions
What do you mean by health?
Health is a state of being well enough to function well physically, mentally and socially and not merely the absence of disease. In order to keep good health, we need to take food full of nutrients, maintain good personal and domestic hygiene and regular exercise, sleep and relaxation. Our social environment and public cleanliness is also necessary for good individual health.
What do you mean by a disease?
The word disease mean disturbed ease or not at ease. Disease literally means being uncomfortable. When we talk of a disease, we find a specific and particular cause for discomfort.
Is it possible to be in poor health without actually suffering from a particular disease?
Yes, it is possible for a person to be in a poor health without actually suffering from a particular disease. Simply not being diseased is not same as being healthy. In order to keep healthy, we need to be happy if we mistreat each other or are afraid of each other, we can not be healthy. Good health for a dancer means he should be able to stretch his body into different but graceful positions. If the dancer is not suffering from any disease but he is not able to stretch his body according to the dance, he will not be considered in a good health.
How do we know that there is a disease?
How do we know that there is something wrong with the body?
When there is a disease, either the functioning or the appearance of one or more system of the body will change for the worse. These changes give rise to symptoms and sign of disease. So, a headache, cough, loose motion and wound with pus are all symptoms. These indicate that there may be a disease.
Signs of disease are what physicians will look for on the basis of symptoms. Signs will give a little indication of presence of a disease. Physician will also get laboratory tests done to pinpoint the disease further.
What are acute and chronic diseases? Give examples.
Acute diseases: The diseases which last for a short periods of time, are called acute diseases. example : Common cold, influenza, typhoid fever, cholera etc. These diseases if not treated well in time can be fatal. Chronic diseases: Some diseases which last for a long time i.e. one year or more or in’ some cases even as much as lifetime. Examples : Tuberculosis, elephantitis, AIDS, cancers etc. Chronic disease causes prolonged general poor health.
A baby is suffering from loose motions. What are the immediate and contributory causes?
- The immediate cause of loose motions is an infection with a virus or bacteria.
- The lack of good nourishment or poor nourishment and genetic difference are the other contributory causes of the disease. Because without virus, the genetic difference and poor nourishment alone would not lead to loose motions.
- The poor public services such as supply of uncleaned drinking water in the area where the family lives, is the third possible cause of disease.
What are infectious diseases and non infectious diseases? Give examples?
Infectious diseases. Diseases where microorganism or microbes are the immediate causes are called inflectious diseases. This is because these microbes can spread in the community, and the diseases they cause will spread with them. Example: common cold, influenza, dengue fever, cholera, tuberculosis and anthrax etc.
Non-infectious diseases: These are diseases that are neither caused by infectious agents like microbes nor can spread in the community. Instead, the cause of disease are mostly internal i. e. malfunctioning of body organs.
Example : High blood pressure, Cancer, Stones in different body organs, etc.
Name the different diseases caused by the following organisms.
|Name of Organism||Diseases|
|(i) Virus||Common cold, influenza, dangue fever and AIDS.|
|(ii) Bacteria||Typhoid fever, cholera, tuberculosis and anthrax|
|(iii) Fungi||Many skin diseases like ringworm and athlete foot.|
|(iv) Protozoans||Malaria Sleeping sickness and kala-azar.|
|(v) Worms of different kinds||Elephantiasis, loose motions and other intestinal infection like taeniasis, ascariasis.|
How does cholera spread from an infected person to a healthy person?
Cholera spread from one person to another through water. This occurs if tire excreta from one person suffering from cholera, get mixed with drinking water used by the other healthy people living nearby. The cholera causing microbe Vibrio cholerae will enter new host through the water, they drink and cause disease in them.
How is the AIDS transmitted from one person to another?
AIDS is transmitted from a person to another by the following ways,
- By sexual contact from an infected partner to another.
- The AIDS virus can also spread through blood-to-blood contact with infected person.
- It can also spread from an infected mother to her baby during pregnancy or through breastfeeding.
Give some ways in which AIDS does not spread from one person to another.
AIDS does not spread from one person to another in the following ways.
AIDS is not transmitted by handshakes or hugs or sports like wrestling, or by any of the other ways, we touch each other socially.
How does malaria spread from one person to another person?
Malaria spread from infected person to healthy person by the bite of a female anopheles mosquito. These insects carry the infecting agent plasmodium from sick person to another healthy person and transfer disease from person to person.
What are air borne diseases? Give examples.
The diseases which spread from infected person to healthy person through air are called air borne diseases. For example. Common cold, pneumonia and tuberculosis.
How do the sign and symptoms of a disease depend upon the organ affected by microbes? Explain with example.
The signs and symptoms depends upon the tissues or organ which the microbe targets. For example if the lungs are targeted, 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 headache, vomiting, fits or unconsciousness.
What is AIDS? What is die cause of this disease? What are effects of HIV-AIDS?
AIDS (Acquired Immuno Deficiency Syndrome) is a chronic fatal disease in which immune system of the body is seriously affected. The cause of this disease is a virus which is known as HIV (Human Immuno Deficiency Virus). Many 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. Similarly minor gut infections can produce major diarrhoea, with blood loss. Ultimately, it is these other infections that kill person suffering from HIV-AIDS.
How does the severity of disease manifestations depend upon number of microbes in the body?
The severity of disease depends upon the number of microbes in the body. If the number of microbes is very small, the disease manifestations may be minor, or may go unnoticed. But if the number of microbes is very large, the disease can be severe enough to be life threatening.
Explain why is it harder to make antiviral medicines than antibacteria medicines.
One reason why making antiviral medicines is harder than making anti bacterial 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 there are few virus specific targets to aim at. But bacterial synthesis pathways are different from that used by our cells. So we can easily find a drug that blocks the multiplication of bacteria without affecting our body. This is achieved by antibiotics.
Why is prevention of diseases better than their cure? Give three reason.
Prevention of diseases is better than their cure because
- If someone has a disease, their body functions are damaged and may never recover completely.
- The treatment of disease will take time, which means that person suffering from a disease is likely tube Wed ridden for sometime even if we can give proper treatment.
- The disease, from which a person is suffering, may spread to other person.
What type of drugs should be given to a patient suffering from diseases caused by bacteria and why?
Antibiotics should be given to a patient suffering from diseases caused by bacteria because they commonly blocks the biochemical pathways important for bacteria. Bacteria make cell-wall to protect themselves. The antibiotic penicillin blocks the bacterial processes that build the cell-wall. As a result growing bacteria became unable to make cell-walls and die easily.
What type of diseases are caused by the following.
(a) If lungs are infected by bacteria.
(b) If liver is infected by virus.
(c) If brain is infected by the virus.
(c) Japanese encephalitis or meningitis.
What are the principles of treatment?
The principles of treatment are as follows:
- First the doctor should know the cause of the diseases by examining the patient.
- The doctor should provide treatment that reduce the effect of the disease.
- The doctor should prescribe drugs which can kill the microbes or stop the proliferation of disease causing microbes.
What are two general ways to prevent diseases.?
General ways to prevent diseases are as follows:
- By preventing exposure to infectious microbes.
- The second basic principle of prevention of infection disease is the availability of proper and sufficient food for everyone, so that the functioning of the immune system remain good.
What is the specific way of preventing infectious diseases?
The specific way of prevention of infectious disease is to strengthen the immune system of the body by giving some vaccines. Many vaccines are now available for preventing a whole range of inflections diseases and provide a disease specific means of preventions. There are vaccines against tetanus, diphtheria, measles, polio and many others.
There is a vaccine for hepatitis A, in the market. But the majority of children in many parts of India are already immune to hepatitis A by the time they are five years old? Why is it so?
Some hepatitis viruses, which cause jaundice are transmitted through water. The majority of the children in many parts of India are exposed to the hepatitis A virus through water the time they are five years old. So, they become immune to hepatitis A.
If you had chickenpox once, there is no chance of suffering from it again. Why?
This happens because when the immune system first sees an infectious agent or microbe, it responds against it and then remembers it specifically. So, the next time that particular microbe, or its close relatives enter the body, the immune system responds with even greater vigour. This eliminates the infection even more quickly then the first time around. So, having the disease once is a means of preventing subsequent attacks of the same disease.
Name the physician who discovered the vaccine against smallpox and cowpox?
English physician named Edward Jenner, discovered the vaccine against smallpox. Dr. Jenner realised that milkmaids who had cowpox did not catch the smallpox even during epidemics. Cowpox is a very mild disease. Jenner tried deliberately giving cowpox virus to the people and found that they were now resistant to smallpox. This was because smallpox virus is closely related to cowpox virus. In this way Dr. Jenner discovered the vaccine against smallpox.
Long Answer Type Questions
Why do we fall ill? What does disease look like.
There are many tissues in the body. These tissues make up organ systems that carry out body functions. Each of the organ systems has specific organs as its parts, and it has particular functions. For example digestive system has the stomach and intestine, and it helps to digest food taken in from outside the body. The musculoskeletal system, which is made up of bones and muscles, holds the body parts together and helps the body move.
When there is any disease either the functioning or the appearance of one or more systems of the body will change for the worse. These changes give rise to symptoms and sign of diseases. Symptoms of disease are the things we feel as being wrong, i.e, if our digestive system is not good, we have loose motion or constipation or pain in the stomach or some gastric trouble.
If our lungs are infected than we loose our weight, become short of breath, feel tired all the time, have fever, cough. These symptoms indicate the tuberculosis of lungs. If we have headache it means just examination stress for any other type of stress or, very rarely, it may mean meningitides or any of the other disease on the basis of certain laboratory test.
Only symptoms do not indicate what the disease is. On the basis of symptoms, the physician get laboratory test i.e. blood sugar, blood pressure, x-ray of a certain organ etc. to pinpoint the disease further.
What do you mean by the (a) immediate cause and (b) contributory cause of a particular disease ? Explain with the help of an example.
There are many causes of a particular disease. These causes inlude:
(a) Immediate cause. Immediate cause of a particular disease may be a infectious agents mostly microorganism such as virus, bacteria, worms or protozoans etc. The disease where microbes are the immediate cause are called infectious diseases.
In some diseases immediate cause are not infectious agent such as some cancer. These are caused by genetic abnormalities or heart diseases caused by malfunctioning of heart.
(b) Contributory causes. The microbes can spread in the community due to unhygienic condition or poor nourishment. Thus, unhygienic conditions, poor nourishment are the contributory causes.
Example. If there is baby suffering from loose motions, we can say that the cause of the loose motions is an infection with a virus. So, the immediate cause of the disease is a virus. We find that this virus came through unclean drinking water. But many babies must have had this unclean water. So, why is it that only one baby developed loose motion while the other babies did not.
One reason for the infection is that baby is not healthy because he is not well nourished and does not get balanced diet. So, genetic difference, lack of good nourishment and unclean drinking water are contributory causes of loose motion. Without the virus, the poor nourishment or genetic difference alone may not lead to loose motion.
What are the different types of infectious micro-organisms which cause infectious diseases? Also give the diagrams and the diseases caused by some of these organisms.
Organism that can cause disease are found in a wide range of categories of classification. Some of these are viruses, bacteria, fungi, single-celled animals or protozoans and worms of different kind.
(i) Virus: All virus live inside host cells and multiply very quickly. The diseases caused by viruses are common cold, influenza, dengue fever SARS and AIDS.
The picture of the SARS virus coming out of the surface of an infected cell is shown below.
(ii) Bacteria: Bacteria are organism which are closely related to each other which means many important life process are similar in the bacteria group. Diseases like typhoid fever, cholera, tuberculosis and anthrax are caused by bacteria.
The picture of staphylococci, the bacteria which can cause acne, is shown below.
(iii) Protozoans: Protozoans are single celled animals. These microbes causes many familiar diseases such as malaria and kala-azar. Some protozoa also cause sleeping sickness. The protozoa, leishmania is shown in the figure causes kalaazar. The organism is oval shaped and each has one long whip-like structure.
(iv) Worms: Some worms like roundworm, tapeworm live in the intestine. Ascariasis and Taeniasis diseases are caused by the roundworm and tapeworm respectively. The disease elephantiasis is also caused by a species of worms.
The pictures below shows the roundworm. This type of roundworm live in small intestine.
How do infectious diseases spread from infected person to healthy person? Give any four ways with examples.
Many microbial agents can commonly move from an affected person to someone else (healthy person) in different ways. These diseases can be communicated from one person to another, so these diseases are called communicable diseases. These communicable diseases can spread by the following ways.
(i) By air. Common cold, preumonia and tuberculosis spread through air from one person to another. This occurs through the little droplets thrown out by an infected person who sneezes or coughs. Some one standing close by can breathe in these droplets and the microbes get a chance to start new infection. Obviously, the more crowded our living conditions are, the more likely it is that such air bone diseases will spread.
(ii) By water. The diseases like cholera, jaundice spread through water. This occurs if the excreta from some one suffering from an infectious disease, such as cholera, get mixed with the drinking water used by the people living nearby. The cholera causing microbes will enter new hosts through the water they drink and cause diseases in them.
(iii) By sexual contact. Some diseases like HIV- AIDS are transmitted by sexual contact from one partner to the other. However, such sexually transmitted diseases do not spread by physical contact such as hand shakes or hugs or sports like wrestlings.
(iv) By Blood to Blood contact: The AIDS virus can also spread through blood-to-blood contact from an infected people. It can also spread from an infected mother to her baby through breast feeding or during pregenancy.
(v) By other creature or animals. Many diseases are transmitted from infected people to the other healthy people through other animals. These animals carry the infecting agents from a sick person to another potential host or healthy person. These animals are called vectors.
The commonest vectors are mosquitoes. The female mosquitoes need highly nutritious food in the form of blood in order to be able to lay mature eggs. Thus, the malaria causing microbes entering through a mosquito bite, will go to the liver and then to the red blood cells. The virus causing Japanese encephalitis or brain fever also enter through mosquito bite.
What are the principles of treatment of infectious diseases? Explain with the help of examples.
There are two ways to treat an infectious diseases:
(i) One would be to reduce the effect of the disease; we can provide the treatment that will reduce the symptoms. The symptoms are usually because of inflammation. For example, we can take medicine that bring down the fever, reduce pain or loose motions. We can take bed rest so that we can conserve our energy. But this kind of symptom-directed treatment by itself will not make the infecting microbes go away and the disease will not be cured.
(ii) The second way is to use medicine that kill the microbes which are main cause of disease. Microbe are classified in different categories. As each groups of microbes have some essential biochemical life process which is peculiar to that group and not shared with the other group. These pathways or processes are not used by us either.
For example : Our cells may make new substances by a mechanism different from that used by the bacteria or virus. We have to find a drug that blocks the bacterial synthesis pathway without affecting our own. The antibiotic drugs blocks the synthesis pathways related to the bacteria. Similarly, there are drugs which kill the protozoa such as malarial parasite. There are antiviral drugs also which can keep HIV infection under control.
What are the principles of preventing infectious diseases?
The principles of preventing infectious diseases are as follows:
1. The general way of preventing infectious diseases mostly relate to the preventing of exposure to the infectious microbes.
For Example: In case of airborne microbes, we can prevent ourselves by providing living condition that are not over crowded. For water home microbes, we can prevent exposure by providing safe drinking water. The. drinking water should be filtered and free from any microbial contamination.
For vector-borne diseases, we require clean environment or we can say that the public hygiene is the basic key to prevention of infectious diseases. Clean environ-ment would not allow any mosquito breeding. We can prevent the spreading of disease like malaria and Japanese fever etc.
2. The second basic principle of prevention of infectious diseases is the availability of proper and sufficient food for everyone. The functioning of our immune system in our body will not be good if proper and sufficient nourishment food is not available. The immune cell manage to kill the microbes. If the number of infecting microbes are controlled, the manifestation of disease will be minor.
3. The infectious diseases can be prevented by immunisation. In general, we befool the immune systems to develop a memory for a particular infection by putting something, that mimic the microbes we want to vaccinate against, into the body. This does not actually cause the disease but this would prevent any subsequent exposure to the infecting microbe from turning into actual disease.
Many such vaccines e.g. vaccines against tetanus, diptheria, measles, polio etc. are available. These provide a disease-specific means of prevention.