Class 12 Biology Human Health Disease Bacterial diseases

Bacterial diseases


  • Caused by Salmonella typhi.
  • Affects small intestine and then migrates to other parts of the body through blood.
  • Transmitted by contaminated food and water.
  • Symptoms- Sustained high fever (39° to 40°C), weakness, stomach pain, constipation, headache and loss of appetite, intestinal perforation and death may occur in severe cases.
  • Typhoid fever is confirmed by Widal test.

fig. Salmonella typhi  


  • Caused by Streptococcus pneumoniae and
  • Affects alveoli of lungs.
  • Transmitted by dropelts released by infected person, sharing glasses and utensils.
  • Common symptoms are fever, chills, cough and headache and in severe cases lips and finger nails turn gray to bluish colour.

fig. Streptococcus pneumonia  

Share these Notes with your friends  

< Prev Next >

You can check our 5-step learning process