Basic Science Notes

Disease Prevention


-Water borne diseases; cholera, diarrhea, typhoid.

-Sources of clean water

-Water treatment processes

-Immunization against human diseases

Sub-topic 1

Water borne diseases

Diseases caused by unclean (dirty) water are called water borne diseases. The following are some of the water borne diseases.

  • CHOLERA: It is caused by harmful bacteria that inflame the intestine and cause extreme diarrhea. Cholera is the most common diseases that can be contacted by drinking unclean water.

 The symptom of cholera is frequent stooling with vomiting which lead to dehydration. Cholera can be prevented by boiling water before drinking.

    2. DYSENTRY: It can be caused by a one-celled animal called                     

Amoeba or by certain bacteria.

3. DIARRHOEA: the symptom of diarrhea is frequent stooling which leads to dehydration, abdominal pains, bloating of the belly, feverish conditions and cramps. To prevent diarrhea, the food we eat and our drinking water should be hygienic. 

4. TYPHOID: It is caused by bacteria called salmolena typhi. Symptoms of typhoid fever manifest within three weeks of infection.

            Symptoms include feeling cold, serious headache, running stomach,

Constipation, enlarged liver and spleen and high fever. Typhoid fever could be prevented by boiling water before drinking, hygienic handling of food and being immunized against the diseases.

Sources of clean water.

1 Pipe-borne water

2 Spring water.

3 Rain water

4 Deep well water


 Mention three borne diseases.   

List the sources of clean water.

Sub-topic: 2: Water treatment processes

        FILTERATION: – This is the process of removing impurities i.e. mud,                   soil, leaves from water. Filter paper is used in the laboratory while filter beds are used at water co-operations.

CHLORINATION: – Chlorine gas is added to water to kill bacteria. It is harmless to human beings. It is also used to purify the water in swimming pools.

DISTILLATION: – This is a process of obtaining pure water from impure water by using an apparatus called Lie Bib Condenser.

DESALINATION: – This is the process of taking away salt from sea water.

           FLOCCULATION: This is the dissolution and stirring of alum in water to make tiny solid particles suspended in water to stick together (flocculate).

Advantages of using pipe-borne water

1. It is clean and colourless.

2. It is odourless.

3. it is tasteless.

4. It is conveniently available in the home.

5. It is treated to kill disease-causing living organisms.

6. Suspended matter has been removed.

Sub-Topic 3


Immunization is a method of stimulating resistance against specific diseasesin the human body using microorganisms (bacteria or viruses) that have been modified or killed. It is also called vaccination or inoculation. The system in the body that keeps disease-causing organisms from entering our body is called Immune system. Immunization of the child begins during pregnancy. The deadly diseases that require immunization are Polio, chickenpox, Pneumonia, measles, whooping cough, hepatitis, malaria, tuberculosis, cholera, tetanus diphtheria etc.

NO Type  of vaccineTo preventAge givenNo. of time givenMinimum interval between age
1Oral polioPolioAt birth, 6 weeks, 10 weeks, 14 weeks       4       4 weeks
2MeaslesMeasles9 months     1               ——
3BCGTuberculosisAt birth, 0-11 months       1    ——
4DPTDiphthera,  whooping cough, tetanus6 weeks 10 weeks 14 weeks      34 weeks
5TetanusTetanusTT1-Early pregnancy TT2[4 weeks] TT3[6 weeks] TT4[1year] TT5[4 years]             5            4 weeks

Where to get immunization is a reputable hospital e. g government hospital around you.


  1. Name three diseases that are caused by unclean water
  2. What are anti-bodies? Explain how they work
  3. list all the methods of purifying unclean water
  4. What is immunization?

 Reading assignment: read basic science made easy by F.I. Kehinde pages 48-55.

Weekend assignment:

1. List examples of diseases immunization can prevent.

2. Write down the time table for various immunizations.

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