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Note on Viruses

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  • Virology: The branch of science which deals with the study of a virus is called virology.
  • Virus: Virus is the smallest Non-Protoplasmic body which often causes disease.
  • Some of the viruses are rich in minerals and vitamins. E.g. Smallpox virus contains (Riboflavin and Biotin)
  • Size of virus: 25 nanometer to 250 nanometers 1nm=10-9m
  • The virus is the obligatory parasite. The virus can reproduce only inside the living host so they are called obligatory parasites.
  • The virus is called borderline between living and non-living thing. Virus behaves like living thing inside the living host but behaves like non-living thing outside of the host. So, it is called borderline between living and non-living thing.

Living characters of a virus:

  • They are made up of nucleic acid i.e. DNA and RNA.
  • They can reproduce inside the living cells.
  • They can cause diseases.

Non-living characters of a virus:

  • They do not perform metabolic activities like digestion, respiration etc.
  • They can be crystallized.
  • They become inactive outside the living cells.

The virus is host-specific: It is because certain types of viruses attack only the certain type of host cell. So, they are said to be host-specific for e.g. Rhino virus attacks only the nasal tissues but cannot infect the blood.

Classification of a virus:

Plant virus: The virus that attacks plant is called plant virus. E.g. - TMV (Tobacco Mosaic Virus) is one of the e.g. of a plant virus. Plant viruses are less host-specific because they can attack not only the particular plant but different species of plants.

Animal virus: The virus, that attacks animals tissues is called an animal virus.

Bacteriophages: The virus that infects bacteria is known as bacteriophages. Actually, bacteriophages are the eater of bacteria.

Bacteriophage virus

S.N Name of the disease/incubation period Causative agent Mode of transmission Symptoms Affected organs or Control measures
1 Common cold (1-3) days. Rhino virus (Droplet infection.) (Direct or indirect contact.) (Runny nose.) (Sneezing and Coughing.) (Headache and Watery eyes.) Upper parts of respiratory tract. (Taking antibiotics.) (Take vaccination.)
2 Measles (10-12) days Paramyxo virus (Droplet infection.) (Direct contact.) (Kissing.) (Runny nose.) (Dizziness.) (Sore throat.) Mouth, skin, respiratory tract, intestine. (Vaccination) MMR.
3 Polio (9-14) days Polio virus (Through faeces.) (Nasal secretes.) (High fever.) (Headache.) (Paralysis.) Pharynx, blood, intestine, spinal cord (Vaccination) Polio Drops.
4 Mumps (12-26) days Paramyxo virus (Droplet infection.) (Through faeces.) (Swelling of the paratid.) (Swelling of breasts.) (Severe fever.) Testes of male, breasts of female. (Vaccination) MMR
5 Rabies (14 days too many months.) Rhabdo virus (Bite of rabid animal.) (Through saliva.) (Fear of water.) (Headache.) (High fever.) Spinal cord Salivary. (vaccination)
6 AIDS (15-75 months.) Retro virus (Unsafe sexual intercourse.) (Infected blood transfusion.) (Fever.) (Cough.) (Pneumonia.) Blood (Avoiding unsafe sexual contact.) (Avoiding use of drugs.)


It stands for Acquired Immune Deficiency Syndrome as immunity power of the body is drastically reduced. (HIV/AIDS) itself is not a disease but promotes many diseases. Due to AIDS, the immune system of the body is totally reduced. As a result, the disease-fighting capacity of the person become weak and s/he will be very likely to be attacked by the germs of other diseases. Therefore, we say that (HIV/AIDS) is not a disease in itself. The person dies off due to her/his poor immunity power.

  • Virus is the smallest Non-Protoplasmic body which often cause disease.
  • The branch of science which deals with the study of virus is called virology.
  • Virus has both living and non-living characters.
  • Rhino virus causes common cold.
  • Paramyxo virus causes measles and mumps.
  • Polio virus causes polio.
  • Retro virus causes aids.

Very Short Questions

Virus is the smallest micro organism. As they survive and reproduce only inside other organisms, viruses are called obligatory parasites.

The two characteristics of virus that make it living are:

  1. They have genetic material, DNA and RNA
  2. They reproduce in large numbers while inside the other organisms.

  1. They do not have a cellular structure.
  2. They do not synthesize proteins.

There are two types of virus. The virus that has DNA as its genetic material is called DNA virus e.g. Bacteriophage. The virus that has RNA as its genetic material is called RNA virus e.g. HIV.

The three preventive measures of AIDS are-

  1. The needle to be used should be sterilized or a new one. Used needles should not be used again.
  2. Sex relation with AIDS patients or unsafe sexual relation should be avoided.
  3. HIV free blood should be used during blood transfusion.

A preventive measure for polio is the administering of polio drops. Rabies can be prevented by using anti-rabies vaccine.

The full form of AIDS is Acquired Immuno Deficiency Syndrome. The four main methods by which the virus that causes AIDS gets transmitted from one person to another are:

  1. Through the transfusion of blood contaminated with AIDS virus.
  2. Through unsafe sex relationship.
  3. Through the use of virus infected needles.
  4. Through AIDS infected mother to the child.

Polio virus attacks nervous system and affects the motor nerve resulting in high fever and stiff neck. When virus weakens the musculature, polio victims become paralyzed.

The person suffering from AIDS may die of any other disease because AIDS makes immune system very weak and the body cannot fight against any invading organisms.

As the dog or human infected with rabies virus has fear of water, rabies is called hydrophobia.

Any virus that has RNA as its genetic material and is involved in making DNA from RNA is called a retro virus. HIV is a retro virus.

The structure that covers the genetic material of the virus is called capsid. It is made up of small protein units called capsomeres.

Based on the nature of host cells, there are three types of virus- Animal virus (attacks animals), plant virus (attacks plants) and Bacteriophages (attacks bacteria).

HIV- Human Immunodeficiency Virus AIDS- Acquired Immunodeficiency Syndrome DNA- Deoxy ribo Nucleic Acid RNA- Ribo Nucleic Acid

In some people, the T cells decline and opportunistic infections that signal AIDS develop soon after. But, most people do not develop symptoms for 10-12 years and a few remain symptom-free for much longer. As with most diseases, early medical care can help prolong a persons life.

You cannot tell by looking at someone whether he or she is infected with HIV or has AIDS. An infected person can appear completely healthy. But, anyone infected with HIV can infect other people, even if he or she has no symptoms.

The viruses are called host species because they attack only a particular type of host or a particular type of tissue. Generally, virus that attack a particular type of host do not attack other types of hosts.

Virus is the smallest microorganism. As they survive and reproduce only inside other organisms, viruses are called obligatory parasites.

The causes of the given diseases are:-

  1. Common Cold - Rhino virus
  2. Mumps- Paramyxo virus
  3. Measles- Paramyxo virus

The preventive measures are:

  1. Common Cold - It can be prevented by controlling the spread of droplets, taking rest and avoiding cold.
  2. Mumps - It can prevented by controlling the spread of droplets during sneezing.
  3. Measles - It can be prevented by using anti-measles vaccine.

As the virus of AIDS (HIV) is found only in body fluids, AIDS does not transmit through kissing.

The modes of transmission of the given diseases are:-

  1. Rhino virus = It is transmitted through nasal secretion and sneezing.
  2. Paramyxo virus = It is transmitted through saliva and nasal secretion.
  3. Polio virus = It is transmitted through saliva, nasal secretion and stool.
  4. Rabies virus = It is transmitted through saliva.
  5. HIV = It is transmitted through unsafe sex, contaminated blood and virus infected syringe.

The organs or parts of the body that are affected in the given diseases are:

  1. Common Cold - Upper respiratory tract.
  2. Mumps- Respiratory tract, salivary glands and whole body through blood.
  3. Measles- Mouth, respiratory tract, skin an intestine.
  4. Polio- Pharynx, intestine, blood and spinal cord.
  5. Rabies- Spinal cord.
  6. AIDS- Skin, blood and brain.

AIDS is a disease in which body's immune system breaks down and is unable to fight off infections, known as 'opportunistic infections' and other illness that take advantages of weakened immune system.

The two differences between a virus and other living things are:

A virus
Other living things
  1. A virus has no cellular structure.
  1. Other living things have a cellular structure.
  1. A virus cannot synthesize proteins on its own.
  1. Other living things can synthesize their own proteins.

The smallpox virus contains vitamins like riboflavin and biotin.

The study of virus called virology

  • AIDS full name is ______.

    Acquired Immuno Deficiency Syndrome
    Acquired Immune Deficiency System
    Acquired Immunity Deficiency Syndrome
    None of above
  • The virus that infects bacteria is known as ______.

    Plant virus
    Animal virus
  • Which one of the following is living characters of virus?

    Made up of nucleic acid i.e. DNA and RNA.

    Cause diseases.

    All of them

    Reproduce inside the living cells.

  • Who discovered virus?

    Adolf Mayer
    Adam Mayer
    Adolf Mendeleev
    William Mayer
  • What is the full form of TMV?

    Tomato Minor Virus
    Tobacco Minor Virus
    Tobacco Mosaic Virus
    Turnip Mosiac Virus
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Forum Time Replies Report
Common cold can transfer through kiss and hug but not AIDS


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Virus is biological puzzle.Why??Answer it as soon as you can...

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Is it possible to reproduce virus in artificial medium?

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Every HIV infected people do not suffer from AIDS??? Plz ans me fast.....

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