VIRUS
Virus is a small substance made of nucleic acids and proteins. Viruses cannot live freely in nature. They can exist only inside other cells. They can take over the metabolism of the host cell, produce more viruses and ultimately kill the host cell.
Differences between Virus and Bacteria
| Virus | Bacteria |
|---|---|
| Very small | Large |
| Visible only under an electron microscope | Visible under a light microscope |
| Non-cellular | Single-celled |
| Have no metabolism | Have metabolism |
| Do not take in any food | Take in food by absorption |
| Do not grow and divide | Grow and divide to produce more bacteria |
| Can be crystallized | Cannot be crystallized |
| Command the host cell to produce virus | Self-reproducing |
| All produce diseases in man, animals or plants | Some harmless, some useful and some disease-producing |
Also Read Bacteria ~ Useful & Harmful Bacteria
Common Viral Diseases
Poliomyelitis (Polio virus):
| Incubation Period | 7–14 days |
| Mode of Transmission | Excreta or secretion of the nose; incubates in the intestine, passes to the brain through the blood vessels |
| Symptoms | Muscle paralysis of legs Common cold, sore throat, fever, fatigue, headache, vomiting and reddening of the throat |
| Preventive Measures | Vaccination, polio vaccine |
Mumps (Myxovirus parotitis):
| Incubation Period | 12–26 days |
| Mode of Transmission | Contact, contaminated food or milk and air |
| Symptoms | 1. Characteristic painful swelling of salivary glands 2. Pain while opening the mouth, earache, headache and fever |
| Preventive Measures | 1. Avoid sexual contact 2. Vaccination of gamma globulin 3. Complete isolation |
Rabies (Rhabdovirus):
| Incubation Period | 30 days or more |
| Mode of Transmission | Mad dog bite (canine disease) |
| Symptoms | 1. Hydrophobia 2. Attacks the central nervous system |
| Preventive Measures | Immunization of the dog |
AIDS (HIV) ~ Read here
Chicken pox ~ Read here
Hepatitis (Hepatitis A ) ~ Read here
Hepatitis (Hepatitis B ) ~ Read here
Hepatitis (Hepatitis C ) ~ Read here
Hepatitis (Hepatitis D ) ~ Read here
Hepatitis (Hepatitis E ) ~ Read here
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