Viruses , smaller than any other organisms, are too small to be seen with ordinary light microscopes unless aggregated to form inclusion bodies. Virus particles called virions, ( not cells), at their simplest ( as in virus of poliomyelitis ) are < 0.03micrometre in diameter - consisting of a genome nusleic acid core with a surrounding capsid protein coat. The nucleic acid found in a virus of any given type is either RNA or DNA, but not both as in bacteria or other cellular organisms. Viruses increase in number not by fission but by replication inside host cells that they have invaded, and are thus obligate intracellular parasites. Outside of living cells viruses exist as inert macromolecules. Some of the commonest infectious diseases in the world are virus diseases, and virus infections may be dealt with under four headings for the sake of clinical convenience.

i) Virus diseases with prominent skin rashes ; - such as measles, rubella, chickenpox, smallpox.

ii) Virus infections of the respiratory tract ;- such as the common cold, influenza, mumps.

iii) Virus infections of the nervous system ;- such as poliomyelitis, meningitis, rabies.

iv) other virus infections , e.g. glandular fever (kissing disease) , and A.I.D.S

Some viral infections can be prevented by vaccination; and anti-viral drugs are often helpful in the treatment of conditions, such as those caused by the herpes virus.     

 #                Thus there are a vast number of microbes of many different types , some of which are beneficial, some harmless, while others cause disease and death to human beings. An understanding of these micro-organisms is essential for nurses to be able to apply principles of asepsis and infection prevention and control. Principles of personal, hospital and community hygiene are based on microbiology. Personal health-related matters such as bathing, room ventilation and eating habits etc - as well as the major public services of water supply, drainage and sanitation all touch upon concerns of microbiological interest. In hospital, because of lowered resistance of sick patients and greater concentrations of pathogenic organisms, faulty hygiene is more likely to cause serious outbreaks of infections spreading rapidly among patients and staff.                         

                    Microbial disease can be prevented by (a) eliminating sources of the responsible organisms ; (b) preventing transmission of the responsible organisms ; (c) raising the resistance of potential hosts so that they are not susceptible to the attacks of the organisms: and procedures for disinfection and / or sterilization should be widely understood. Before changing patients' surgical dressings it is important to 'scrub up' in a systematic manner. Nails are washed , then backs of hands & fingers, webs between fingers at the back, and finally the front of hands and fingers. Masks are worn to prevent bacteria from the wearer's respiratory tract reaching susceptible people; and they can also protect the wearer from infection, e.g. when nursing patients with open tuberculosis. Everything possible should be done to prevent staff to patient or patient to patient transference of microbes. It is recommended that spacing between bed centres should be > 8feet, and corridors between bed rows > 10ft wide.

                    Those particularly vulnerable include newborn infants and premature babies , mothers during labour, surgical patients - especially during operations or wound dressing -, patients with deep-seated systemic diseases or invasive catheters in situ ; patients undergoing renal dialysis ( c.f. algae above ) , and those immobilised for orthopaedic reasons. Correct disposal of infected instruments & linen, clinical waste and used sharps ; as well as the regular cleansing of ordinary cutlery, crockery and food utensils all require awareness of risks of transmission and possible routes of infection. Whilst it is immediately apparent the advantages to be gained from expanding knowledge and cleanliness through microbiological discovery - there is little that can be argued on behalf of ignorance and dirtiness in either nursing practice or health care.