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What Communicable Diseases Are
- Caused by biological agents or pathogens
- Include viruses, bacteria and protozoa
- Also helminthes, nematodes and fungi
- They spread rapidly from person to person
- Also called infectious diseases
- caused by a virus
- spreads through contaminated air
- passes to a healthy person
- caused by bacteria
- spreads by infected food or water
- communicated to healthy people
- They spread by physical contact, indirect contact, water, air, food and insects.
- Examples: cold, cholera, chickenpox, TB, malaria, COVID-19, AIDS.
- Because they pass from a diseased to a healthy person, they are infectious.
Transmission of Communicable Diseases
- Pathogens enter through air, water or food
- Also by contact with an infected person
- Insects can carry them too
- Insects that spread disease are vectors
- Sharing infected needles also spreads them
- spreads through mosquito bites
- the mosquito is a vector
- caused by a protozoan
- spreads by sharing infected needles
- also by physical contact
- passes from infected to healthy person
- Five ways: air, infected food/water, insect bites, infected needles, physical contact.
- Using an infected person's towel or utensils can spread disease.
- Insects such as mosquitoes acting as carriers are called vectors.
Diseases by Various Pathogens
- Different microbes cause different diseases
- Bacteria cause TB and typhoid
- Viruses cause cold and measles
- Protozoa cause malaria and dysentery
- Fungi cause ringworm and athlete's foot
- common cold infects respiratory tract
- measles affects skin and respiratory tract
- prevented by covering mouth and nose
- typhoid and cholera infect the intestine
- spread by contaminated food and water
- prevented by drinking boiled water
- Hepatitis A is a virus that infects the liver.
- Chickenpox affects the skin; tuberculosis affects the lungs.
- Yellow fever, chikungunya and dengue are spread by mosquitoes.
Prevention of Communicable Diseases
- Cover mouth and nose while sneezing
- Keep food covered and water clean
- Use mosquito nets and repellents
- Use only disposable syringes
- Avoid contact with an infected person
- cover mouth with a handkerchief
- keep distance from a sick person
- fewer microbes reach the air
- use mosquito nets while sleeping
- fix wire mesh on windows
- remove stagnant water nearby
- An infected person's towel and utensils should be washed separately with soap and hot water.
- Some diseases can be prevented by vaccination at the proper time.
- Keeping safe distance from a sick person reduces spread.
Name the following: The microorganism which causes common cold.
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Explanation
- Common cold is caused by a virus and spreads through air.
Name the following: The site of infection by measles.
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Explanation
- Measles is caused by a virus affecting the skin and respiratory tract.
Name the following: The insect which causes yellow fever.
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Explanation
- Yellow fever is a viral disease transmitted by mosquito.
Fill in the blank: Malaria is a type of ________ disease.
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Explanation
- Malaria spreads from person to person through a mosquito vector.
Fill in the blank: The insects which spread diseases are called ________.
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Explanation
- A mosquito carrying malaria is an example of a vector.
Fill in the blank: ________ is spread through injection needles or sexual contact.
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Explanation
- AIDS spreads by sharing infected needles or by physical contact.
Fill in the blank: Tuberculosis is caused by ________.
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Explanation
- Tuberculosis (TB) is a bacterial disease affecting the lungs.
Fill in the blank: Hepatitis A virus infects the ________.
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Explanation
- Hepatitis A spreads through contaminated food and water.
Match the pathogen to the disease it causes: (a) Fungi (b) Roundworm (c) Virus (d) Protozoa (e) Bacteria — with (i) Chickenpox (ii) Cholera (iii) Food poisoning (iv) Ascariasis (v) Malaria.
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Explanation
- Fungi → Food poisoning.
- Roundworm → Ascariasis.
- Virus → Chickenpox.
- Protozoa → Malaria.
- Bacteria → Cholera.
Classify the following diseases into communicable and non-communicable: Diphtheria, Swine flu, High blood pressure, Measles, Diabetes, Hypertension, Typhoid, Chickenpox, Giardia.
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Explanation
- Communicable: Diphtheria, Swine flu, Measles, Typhoid, Chickenpox, Giardia.
- Non-communicable: High blood pressure, Diabetes, Hypertension.
Which disease(s) among the following may spread if drinking water gets contaminated by the excreta from an infected person? Hepatitis A, Tuberculosis, Poliomyelitis, Cholera, Chickenpox. (NCERT Book Question)
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Explanation
- These spread through contaminated food and water.
- Tuberculosis and chickenpox spread through air, not water.
State the differences between communicable and non-communicable diseases.
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Explanation
- Communicable are caused by attack of pathogens; non-communicable by factors other than living pathogens.
- Communicable are due to external factors; non-communicable mostly due to internal factors.
- Communicable pass from a sick to a healthy person; non-communicable cannot pass between people.
- Communicable spread by contact, air, water or vectors; non-communicable have no transmission (but hereditary ones pass parent to offspring).
- Community hygiene reduces communicable diseases but is ineffective for non-communicable ones.
- Examples — communicable: cold, cholera, TB; non-communicable: diabetes, hypertension, goitre.
Name any five human diseases caused by microorganisms. Also name the causative microorganisms and mode of transmission for each of these diseases.
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Explanation
- Common cold — virus — through air.
- Tuberculosis — bacteria — through air.
- Cholera — bacteria — through contaminated food and water.
- Malaria — protozoa — through mosquito (insect) bite.
- Hepatitis A — virus — through contaminated food and water.
State the various ways of preventing the occurrence and spreading of communicable diseases.
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Explanation
- Cover mouth and nose with a handkerchief while sneezing and keep distance from a sick person.
- Keep food covered and drink clean, safe water.
- Use mosquito nets, wire mesh and repellents against mosquito bites.
- Use only disposable syringes and needles for injections.
- Avoid physical contact and sharing items with an infected person; wash their items separately with soap and hot water.
- Get vaccinated at the proper time.
Which among the following will act as a vector?
- (a) mosquito
- (b) virus
- (c) protozoa
- (d) fungi
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Explanation
- A vector is an insect that carries pathogens; the mosquito is a vector.
Which disease is spread by contaminated food and water?
- (a) pertussis
- (b) cholera
- (c) malaria
- (d) tuberculosis
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Explanation
- Cholera spreads through contaminated food and water and infects the intestine.
The carrier of malaria-causing protozoan is:
- (a) mosquito
- (b) cockroach
- (c) housefly
- (d) spider
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Explanation
- The mosquito is the vector that carries the malarial protozoan.
Which of the following is not a communicable disease?
- (a) cholera
- (b) cancer
- (c) chickenpox
- (d) malaria
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Explanation
- Cancer is non-communicable; it does not spread from person to person.
Which part of the body is affected by chickenpox?
- (a) eyes
- (b) respiratory tract
- (c) skin
- (d) lungs
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Explanation
- Chickenpox is a viral disease that affects the skin with rashes and blisters.
Which of the following diseases is transmitted by mosquito and can cause jaundice?
- (a) influenza
- (b) hepatitis A
- (c) malaria
- (d) yellow fever
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Explanation
- Yellow fever spreads by mosquito and its symptoms include jaundice.
