Biology IX | Health and Diseases | Part 1

Health and Diseases | Part 1

Human Diseases

Definition :

Disease may be defined as a disorder in the physical, physiological, psychological or social state of a person caused either due to nutritional deficiency, hormonal disorder, genetic disorder, pathogen or any other reason.

Types of Diseases

Diseases are broadly grouped into two categories :

a. Congenital diseases

b. Acquired diseases

Congenital Diseases :

These diseases are those which are present since birth. They are caused due to a genetic abnormality or due to metabolic disorders or malfunctioning of any organ or organ system. These disease may be inherited.

Acquired Diseases :

These diseases are those which develop after birth. These can be broadly classified into two types :

(a) Communicable (Infectious) Diseases

These are caused by the attack of microorganism (Pathogens) such as bacteria, viruses, fungi or protozoans. The causal organism of the disease can be transmitted from one person to another by means of air, water, food, physical contact and insects (vectors). Hence, these are called communicable diseases that are communicated from diseases person to healthy person.

(b) Non-Communicable (Non-Infectious) Diseases

The diseases which do not spread from infected person to healthy person are known as non-communicable or non-infectious diseases, such as diabetes, arthritis, heart diseases, cancer, etc. Many non-communicable diseases are due to nutritional deficiency.

Disease caused by Protozoa

Malaria :

Health experts estimate that bout 300 million people are infected with malaria every year and more than 2 million die annually due to malaria. Malaria is caused by a protozoan parasite Plasmodium. This spreads through the bite of an insect vector-female anopheles mosquito which feeds on human blood (male anopheles mosquito feed upon plant juices).

Symptoms :

Headache, nausea, muscular pains and high fever are the main symptoms of malaria. Each malarial attack is of 6 – 10 hours and consists of three states : cold stage feeling very cold and shivering), hot stage (high fever, faster respiration and heart beat) and sweating stage (in which temperature goes down to normal). Malaria may also secondarily cause enlargement of spleen and liver.

Macculoch (1827) proposed the name malaria. Laveran (1880) discovered the malarial parasite Plasmodium in the blood of malarial patient.


1. Use wire-guaze on doors and windows to prevent entry of mosquitoes.

2. Use insect-repellents to prevent mosquito-bite.

3. Sleep under mosquito net.

4. Mosquito larvae should be killed by sprinkling kerosene oil, Cambusia, minnows, trouts and birds (ducks) etc.

5. Kill adult mosquitoes by spraying insecticides

6. Destroy mosquito-breeding places

Control :

A drug named quinine (extracted from the bark of Cinchona tree) is used to treat a person suffering from malaria.

Disease caused by Viruses

Influenza (Flu) :

Symptoms of influenza (Flue) are common cold, cough and fever. It is an air borne disease. The cause disease is a virus called Myxovirus influenzae.

Symptoms :

Sneezing, coughing, fever, etc. are the main symptoms of this disease.

Prevention :

Try to keep away from flue patients.

Control :

There is no effective control for influenza.

Jaundice / Hepatitis :

Jaundice or hepatitis is the disease of liver. Jaundice is caused by viral infection. The types of hepatitis are : Hepatitis – A, B, C, D, E or G Disease is spread mostly by food and water contaminated with hepatitis.


(i) High temperature, headache and joint pains.

(ii) Loss of appetite with a feeling of nausea and vomiting.

(iii) Dark yellow urine and light-coloured stool after 3 to 10 days.


(i) Use chlorinated, boiled and ozonised water.

(ii) Hepatitis – B vaccine should be taken to prevent the disease.


(i) Interferon injection administered on the advice of the doctor will control the disease.

(ii) Adequate rest is essential for an early cure.


Acquired Immuno Deficiency Syndrome (AIDS) is a fatal disease in which immune system of the body is seriously affected. It was first detected in June 1981 in USA. The cause of the disease is a retrovirus-HIV (human immuno deficiency virus). The disease is transmitted from an infected person to healthy person through sexual contact, blood transfusion, use of contaminated needles or blade, or razors and other equipment of barbers and also from infected mother to the foetus.


(i) Decreased count of blood platelets causing haemorrhage and fever.

(ii) Sweating at night and weight loss

(iii) Severe damage to brain which may lead to loss of memory, ability to speak and even think

(iv) Patient becomes susceptible to other infections due to breakdown of immune system


Educating the people for the following :

(i) No common razor should be used.

(ii) A blood donor should be first tested HIV negative.

(iii) Disposable needles and syringes should be used

(iv) Sexual contact with unknown people should be avoided.

Control :

Till date there is no effective treatment for AIDS.


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