Class 9 Science Chapter 13 Why do we fall ill?
Disease is a state in which, body or organs of body show variation. Such changes are called symptoms. Therefore, symptoms indicates presence of disease. However, it does not show what the disease is. Diseases can be either acute or chronic.
Acute diseases
Diseases which last for short period of time is called acute disease. For example, common cold, fever, eye infections, pain, etc.
Chronic diseases
Diseases which last for long time is called as chronic diseases. For example, Kidney disease, heart disease, respiratory disease, etc. Also, it causes prolonged weakness in the body. For example, if person suffers from tuberculosis, the person can face weight loss and long period of weakness providing bad health.
Causes of disease
Diseases can be caused due to various reasons like drinking unclean water or eating contaminated food, lack of nourishment to body, genetic differences carried from parents to children, etc. Therefore, cause of diseases is classified as either non infectious disease or infectious diseases.
Disease
Non infectious disease
Diseases which are not caused by microbes are called noninfectious diseases. Noninfectious diseases do not spread by coming in contact with sick person. For example, High or low blood pressure, heart disease,etc.
Infectious disease
Diseases which are caused by microbes are called infectious disease. Such diseases are spread by coming in contact with sick person. Hence, these microbes are called infectious agents. However, infectious agent can be bacteria, virus, fungi, protozoa, and worms.
| Infectious Agent | Diseases |
|---|---|
| Virus | Dengue fever, Common cold, etc |
| Bacteria | Cholera, Typhoid, Tuberculosis, etc |
| Fungi | Skin diseases like ringworm |
| Protozoa | Malaria, Kala azar, etc |
| Worms | Ascariasis, Elephantiasis, etc |
Therefore, such diseases are cured by killing the infectious agents. As a result, medicines like antibiotics are used to cure bacterial diseases, antivirals are used to cure viral diseases, anti fungal are used to cure fungal diseases. Thus, these medicines stops the growth by killing the infectious agents.
Coronavirus 2019 or COVID 19 is a disease caused due to new strain of coronaviruses which is infectious. There are different types of coronaviruses cause respiratory and sometimes gastrointestinal problems. Respiratory problems include common cold, pneumonia and in many individuals symptoms can be mild. The World Health Organisation (WHO) has declared COVID-19 as pandemic. Hence, it is important to take preventive measures. Social distancing and isolation may lead to boredom, stress and anxiety in people. Checkout https://www.betterhelp.com/advice/general/covid-19-coronavirus-news-ease-symptoms-of-boredom-depression-anxiety-and-chronic-mental-health-while-indoors/ to know more about mental health in coronavirus pandemic.
Modes of Spread of Diseases
Microbes can be spread through air, water, by sexual transmission, or through animals.
- Airborne diseases: Diseases which spread through air are called airborne disease. For example, if person suffers from cold, through the sneeze of such person microbes are thrown out of body. However, if healthy person breathe in this air, person may catch this infection.
- Waterborne diseases: Diseases which spread through water are called waterborne disease. For example, if waste of infected person suffering from cholera is entered in sources of drinking water, and this water is used for drinking purpose then, healthy person easily catch this infection.
- Sexual diseases: Diseases which are spread by sexual contact are called sexual disease. For example, AIDS. It is transferred from infected person to another person during sexual contact. Such disease are also transferred from pregnant mother to baby or while providing nourishment to baby or through blood donation.
- Animal borne diseases: Diseases spread through animals are called animal borne disease. For example. When mosquito bites a person suffering from malaria it carries infectious agent. When this mosquito bites healthy person infectious agent gets inject in healthy person’s body causing malaria.
Keywords: Acute diseases, Chronic diseases, Infectious diseases, Non infectious diseases, Air borne diseases, Water borne diseases, Sexual diseases, Animal borne diseases.
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