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Diseases and First Aid — BIOLOGY STD 8 — Question

ICSE BoardEnglish MediumSTD 8BIOLOGYDiseases and First Aid5 Marks
Question
Describe the ways in which communicable diseases are transmitted through various indirect methods.
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Answer

Indirect methods of transmission of communicable diseases :
$1.$Using items used by the infected persons : The healthy persons may be infected by using the articles like towel, hankey, utensils, bedding used by the patient infected by the communicable diseases. Diseases like tuberculosis, ring worm; common cold, influenza are transmitted by this method.
$2.$Contaminated food and water : Diseases like dysentery, cholera spread through the contaminated food and water. Flies sitting on the food, if taken by a healthy person may be infected by the germs which may cause vomiting and loose motions. Similarly water and food infected by entamoeba may cause dysentery to persons who may take contaminated food.
$3.$Vectors or carriers : Organisms like mosquitoes and house flies, ticks carry germs from the source of infection and pass on the germs to the normal persons and thus they are infected by diseases like malaria, cholera, plague. These organisms which carry the disease are called vectors and are not infected themselves.
Mosquitoes suck blood and carry the disease causing protozoans from infected persons to healthy persons.
Similarly houseflies carry the germs from garbage and sewage to the food. If this food is taken by the persons they become prey to typhoid and other diseases.
$4.$Air : One sneeze from a person infected by cold may give billions of germs which are carried by air and may infect the healthy person. Tuberculosis passes from one person to other by coughing or sneezing of the infected person.
These germs remain suspended in the air and persons may be infected by these spores or germs. Common cold, measles, diptheria, chicken pox.

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