This document discusses viruses and some viral diseases. It defines viruses as being much smaller than bacteria, crystalline in nature, and only able to reproduce inside living cells. It then summarizes three viral diseases: smallpox, which has been eliminated through vaccination; polio, which can paralyze the legs and is prevented by oral vaccination in children; and influenza, a common illness spread through sneezing that resolves within a week with rest and medication.

1. Duration: 95 min Middle School Grade: 6 - 8 CCSS, NGSS
What is a virus?
Viral diseases

2. LEARNING OBJECTIVES

3. virus
They are ultra microscopic organisms much smaller than bacteria
Measured in millimicron (1 millimicron=1/1000 micron)
They can only be seen by electronic microscope and not with compound microscope
Composition:
They become active and reproduce in living cells
only
They are crystalline in nature and have various
shapes and sizes

4. 2. Discussion – Virus, a mortal enemy
1) SMALLPOX
• it is a fatal disease but now has been eliminated
from the world including Pakistan
• Small boils appear on the whole body filled with
pus cells
• The patient must be isolated from rest of family
members
• Its only remedy is vaccine
• The vaccine against smallpox was first to be
discovered

5. 2) POLIO
• This is a disease of infants in which the lower limbs
are damaged making them disable
• Main symptoms: fever, headache and stiffness in
neck
• The legs are paralyzed under severe attack
• It spreads through air and water and children under 5
are victims
• Only remedy is use of polio vaccine at regular
intervals till the age of 5
• Its vaccine is available in form of oral drops
• The government of Pakistan with collaboration with
UNICEF has launched a campaign to vaccinate as
many infants as possible against polio

6. 3) INFLUENZA
• It is a common human disease and not dangerous
and is caused by influenza virus
• The virus spreads through the air and by sneezing
• Symptoms: mild fever, redness of eyes, irritation
in nasals and flow of nose
• This disease automatically diminishes after 4-5
days
• Treatment: complete rest and use of medicine
(drugs)