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What are communicable diseases, and how do they spread?

Class 8 ScienceNCERT chapter: Health: The Ultimate Treasureइसे हिंदी में पढ़ें

Exam-ready answer

Communicable diseases are diseases caused by microorganisms that can pass from an infected person to a healthy person. They spread through air (tuberculosis, common cold), through contaminated water and food (cholera, typhoid), through direct contact with an infected person or their things, and through carriers such as mosquitoes (malaria, dengue). Diseases like diabetes are non-communicable.

Explanation

Some diseases are caused by pathogens such as bacteria, viruses, protozoa and fungi. When these microbes leave an infected person and reach a healthy one, the disease spreads. Such diseases are called communicable or infectious diseases. Diseases like diabetes or high blood pressure are not caused by microbes and do not spread from person to person, so they are non-communicable.

Air is a common route. When an infected person coughs or sneezes, tiny droplets carrying microbes spread in the air and are breathed in by others, as in the common cold and tuberculosis. Water and food can carry microbes when they are contaminated with sewage or handled with dirty hands, causing cholera and typhoid. Some infections spread by touching an infected person or sharing their towels and utensils.

Carriers or vectors are animals that transmit microbes. The female Anopheles mosquito carries the malaria parasite, and the Aedes mosquito carries the dengue virus. Houseflies carry germs from garbage to uncovered food. Covering the nose while sneezing, washing hands, drinking clean water, covering food and not letting water collect around the house all help break these routes.

Points to remember

  1. Communicable disease: a disease caused by microorganisms that spreads from an infected person to a healthy person.
  2. Air-borne: common cold, tuberculosis — spread by droplets from coughing and sneezing.
  3. Water/food-borne: cholera, typhoid — spread through contaminated water and food.
  4. Vector-borne: malaria (female Anopheles mosquito), dengue (Aedes mosquito); houseflies carry germs to food.
  5. Non-communicable diseases like diabetes do not spread from person to person.

Exam tip

Make a small table with three columns — mode of spread, example disease and one prevention step — it is quick to write and easy for the examiner to mark.

Questions students also ask

How can we prevent the spread of communicable diseases?
Wash hands with soap, cover the mouth and nose while coughing or sneezing, drink clean water, keep food covered, keep surroundings clean, stop water from collecting so mosquitoes cannot breed, and get vaccinated on time.
What is a carrier or vector?
A carrier or vector is an organism that carries disease-causing microbes from one person to another without being the main cause of the illness. Mosquitoes and houseflies are common examples.
Is tuberculosis a communicable disease?
Yes. Tuberculosis is caused by bacteria and spreads through the air when an infected person coughs or sneezes. It can be treated, so anyone with a long-lasting cough should see a doctor.

Chapter labels help you find the topic in your textbook. Check your own edition: chapter names and order can change. These are Know.it explanations, not official NCERT solutions.