1. Viruses And How They Work

2. What is a virus?  A non-living particle – reproduces by using a host cell  A VERY small particle – 17 to 300 nanometers long (and remember = 1 nm is 1/1 000 000 000 of a meter)  They are a thousand times smaller than a bacteria!  Unlike a cell, they cannot be seen by a light microscope.

3. What do they look like?  They are of MANY different shapes  They all have a capsid or a protective protein coat  Have a set of genetic instructions DNA or RNA  Some may have a lipid membrane and are called enveloped viruses

4. What are they missing?  There is an absence of organelles  There are no enzymes (proteins) needed to carry out the life processes  They only have one or two enzymes that decode their genetic information  Blocking these enzymes is effective treatment in a disease like AIDS from the HIV virus

5. Viral Infections  Viruses enter through openings – nose, mouth, eye etc  Upon entering they will find a host cell to infect  the influenza virus attack the lining of the respiratory system while HIV attacks the T-cells of the immune system

6. Lytic cycle – The basic steps  Attachment to host – proteins to recognize hosts or some have membranes that are dissolved into the host  Genetic material from virus released into the cell – injected if capsid remains on the exterior of the host  Host enzymes are recruited to do the work – making new genetic pieces or protein coats and capsids  Enzymes make new viral parts  Assembly of the new parts to make new virus particles  New particles break FREE – pinch out through the membrane or breaking open the host cell

7. Inside the cell  One virus creates more that lyse open the cell and new cells are attacked  This loss of host cells inside the respiratory tract allows sinus fluids to flow – the runny nose of the cold!  Viral particles spread to the bloodstream and lungs – resulting in cough and fever  Muscle cells can be attacked and you have the aches of the flu!

8. The Lysogenic Cycle  Some viruses do NOT reproduce right away  The viral genetic information mixes with the host DNA and can remain dormant for a long period of time, reproducing as part of the host DNA – there are no symptoms of the disease at this time – can last for years – HIV and Chicken Pox  A genetic signal or trigger will initiate the takeover of the viral DNA reproducing the genetic code and capsids and the lytic cycle starts which ends in the release of the new virus particles

9. Prevention and Treatments  Spread through carrier organisms, infected persons, the air and on surfaces in the environment  To reduce the spread – cover your mouth when you sneeze or cough – wash hands often- avoidance of others body fluids  Taking care in the presence of peoples with weakened immune systems  Medicines do NOT include antibiotics, but immunization is suggested, (vaccines are modified on a regular basis due to mutations)  Taking care of yourself when infected  Using medicines that block the enzymes of the host cells that have been recruited by the virus particle