Q.Explain the Viral diseases in human beings.

Viral diseases of humans include AIDS, hepatitis, polio, rabies, influenza, common cold, measles, mumps, chicken pox, small pox, dengue and chikungunya — caused by viruses, spread by contact/droplets/vectors/contaminated food, and largely prevented by vaccination and hygiene.

Viruses are extremely small, obligate intracellular parasites — they can multiply only inside living host cells. They cause a large number of human diseases. Since viruses are not affected by ordinary antibiotics, prevention (vaccination, hygiene, vector control) is the main line of defence, and interferons are the promising antiviral agents.

Important viral diseases in human beings:

1. AIDS (Acquired Immuno Deficiency Syndrome): caused by the Human Immunodeficiency Virus (HIV), which destroys helper T-cells and weakens immunity. Spread by unprotected sex, infected blood transfusion, shared needles, and mother to child. There is no cure; prevention is by safe practices.
2. Hepatitis: inflammation of the liver caused by hepatitis viruses (A, B, C, etc.), leading to jaundice, fever and weakness. Hepatitis A and E spread by contaminated food/water; B and C by blood and body fluids. Vaccines exist for A and B.
3. Poliomyelitis (Polio): caused by the polio virus; it attacks the nervous system and can paralyse limbs, mainly in children. Spread through contaminated food/water. Prevented by the polio vaccine (OPV/IPV).
4. Rabies (Hydrophobia): caused by the rabies virus, transmitted by the bite of a rabid dog or other infected animal. It affects the central nervous system, causing fear of water (hydrophobia), and is almost always fatal once symptoms appear. Prevented by anti-rabies vaccination.
5. Influenza (Flu): caused by the influenza virus; a contagious respiratory disease with fever, cold, cough and body ache, spread by droplets.
6. Common cold: caused by rhinoviruses; mild infection of the upper respiratory tract with running nose, sneezing and sore throat.
7. Measles, Mumps, Chicken pox and Small pox: viral fevers with characteristic rashes/swellings, spread by droplets or contact. Measles (measles virus), mumps (mumps virus, swollen salivary glands), chicken pox (Varicella virus). Small pox (Variola) has been eradicated worldwide by vaccination. Preventable by vaccines (e.g. MMR). …