Human Physiology, Diseases, Poliomyelitis or Polio, Diseases Caused by Bacteria

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Human Physiology, Diseases

Measles or Rubella

Causal organism: Myxovirus

Mode of Spread

  • By direct contact with patient.

  • By coughing or sneezing.


Since the incubation period of this virus is 10 days, therefore first symptom appears after 10 days. The symptoms are:

  • Fever, dry cough and running nose.

  • Inflammation of the respiratory mucous membrane.

  • Loss of appetite.

  • Pink or red rashes or eruption appear on the face, neck and trunk. These rashes last for 4-7 days and the marks of dark pigmentation left thereafter disappear after a few days.

  • Vomiting.

  • Eyes become sensitive to light.

  • Contract pneumonia as a secondary infection.

Prevention and Control

  • Passive immunity can be attained by injecting of gamma globulin. This immunity thus developed lasts for only three to four weeks.

  • Isolation of patient and personal hygiene are important to prevent the spread of infection.

  • Use of glycerine or carbonized oil prevents its further spread.

Poliomyelitis or Polio

Causal organism: Entero- virus

Mode of Spread

  • By contaminated food and water.

  • By intestinal discharge of diseased person.

  • Insects and flies play an important role in the transmission of viruses.

Site of Infection

  • The virus enters the intestine through contaminated food. It multiplies in the intestine through contaminated food. It multiplies in the intestine from where it reaches the nervous system through the blood stream i.e., circulatory system.

  • In the spinal cord it causes inflammation of motor cells which control the movement of voluntary muscles. In the absence of nervous control, the muscles wither away and get paralysed.


  • The initial symptoms of the disease are occurrence of fever and stiffness of neck. Due to stiffness of neck, the head cannot bend forward and downward.

  • Skeletal muscles get weakened and paralysed.

  • Movement of limbs becomes weak and finally stops as the muscles fail to contract.

Prevention and Control

  • Poliomyelitis vaccine is quite safe and effective against this disease.

  • All children should be immunised in the beginning of infancy to ensure complete safety against the disease.

  • The immunity can be maintained if booster dose is given every few years. Other viral diseases are Rabies, Small Pox, Trachoma, Influenza etc.

Diseases Caused by Bacteria

Following are some of the important Bacterial diseases in man.


Causal organism: Vibrio cholerae

Mode of Spread

  • By contaminated food and water.

  • By inhalation of droplets expelled by diseased person through coughing, speaking, sneezing or sputum.

  • Flies are the main carrier of these bacteria and spread the disease.

  • Epidemic of cholera usually occurs during fairs and after flood and other such natural calamities.


Since the incubation period of these bacteria is 2- 3 days, therefore symptoms will appear after 2-3 days of infection. The various symptoms of this disease are:

  • Vomiting and acute diarrhoea with rice water stools resulting in dehydration and loss of minerals from body. In acute cases death may also occur.

  • Muscular cramps.

  • Suppression of urine.

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