Harmful microorganisms

• Some of the microorganisms cause diseases in human beings, plants and animals. Such disease-causing microorganisms are called Pathogen.
• The diseases which are caused due to entry of a pathogen into a living system are known as infectious diseases.
• These pathogens can enter the body via different means.

Means of Spread:

Air:

• Air contains micro organisms or pathogens.
• These pathogens can enter the body by the infected air we breathe in and suffer from the diseases like cold, cough etc.

Spread through air

Water:

• Water gets contaminated due to addition of waste or mixing of sewage water in fresh water bodies.
• If the water that we use for drinking or other purposes contains pathogen than we may get infected and suffer from the diseases like dysentery, diarrhoea etc.

Spread through water

Vectors:

• Vectors are the animals that can carry the pathogen from a patient and transmit it to the healthy person.
• For example: houseflies, mosquitoes, dogs etc.

• Houseflies sit on garbage or unclean surfaces, from where the pathogen sticks to its legs. Further when it sits on clean surface or food it drops the infectants (bacteria) over there. Now if we consume such infected food the pathogen enters the body and causes disease like food poisoning.
• Mosquitoes suck the blood from a patient suffering from malaria and carry the malarial parasite- plasmodium (protozoa). Further when it bites the healthy person it transmits the pathogen into it and thus spreads the disease malaria.

• Many other animals can spread other diseases in different ways and are thus known as carriers of disease causing micro organisms.

Direct Contact:

• If we come in direct contact with the infected person we can also get infected.
• Such direct contact includes handshake, hug, kiss, or a sexual contact.

• The examples of such diseases are chicken pox, skin infection, AIDS etc.

Indirect Contact:

• Indirect contact means use of or sharing articles of infected person like food, water, handkerchief etc.
• The examples of such diseases are chicken pox, cough, cold etc.

Some Common Human Diseases caused by Microorganisms:

Disease - causing Microorganisms in Animals:

• Anthrax is a dangerous human and cattle disease caused by a bacterium.
• Foot and mouth disease of cattle is caused by a FMDV virus.

Disease - causing Microorganisms in Plants:

• Several microorganisms cause diseases in plants like wheat, rice, potato, sugarcane, orange, apple and others.
• This can lead to reduced yield of crop.

Some Common Plant Diseases caused by Microorganisms:

General Preventive Measures for Control of Diseases in Humans:

• Keep the surroundings clean.
• Don’t allow water to get collected in the surroundings.
• Keep the patient in isolated conditions.
•  Keep the personal belongings of the patient away from those of the others.
• Maintain personal hygiene and good sanitary habits.
•  Consume properly cooked food and boiled drinking water.
• Drink boiled drinking water.
• Use mosquito net and repellents.
•  Spray insecticides and control breeding of mosquitoes by not allowing water to collect in the surrounding.
• Vaccination to be given at suitable age.