Introduction - transmission of viruses, bacteria and parasites


What is a micro-organism?

Living organisms, too small to detect with the naked eye, were first discovered by a Dutch scientist, Antoni van Leeuwenhoek (1632-1723). Van Leeuwenhoek dedicated much of his time to the grinding of magnifying lenses. He produced the best lenses available at that time, with a magnification of approximately 300 times. Van Leeuwenhoek's amazement while observing the world of microbes could be sensed from one of his letters to the Royal Society regarding a rotten tooth: 

‘I removed this stuff from the root cavities, mixed it with clear water and placed it under a microscope. I have to admit that the stuff looks like it is living. But even so, the volume of those tiny creatures was so extraordinarily large that around a billion would be needed to make up a grain of sand.’

What is a virus?

A virus is a piece of DNA or RNA and is much smaller than the smallest known bacterium. Viruses cannot multiply by themselves and do not stay alive outside the host body. The most important weapon of man against viruses is the immune system. This system functions in two ways: It helps us to recover from a virus disease and protects us from a following infection. Some viruses, like HIV, destroy their host’s immune system. Others have learned to ‘hide’ in cells, specially selected for this purpose and sporadically appear at ‘convenient’ moments. Herpes Simplex, for example - this virus lives in the nervous system of as many as 90% of all adults. If your resistance gets weaker or you have had too much sun, this virus causes cold sores on the lips. The third virus category has developed a mechanism which treats every contact with the immune system as a new encounter, like the flu virus, for example.

What is a bacterium?

Bacteria are single-cell organisms which, in contrast to viruses, can multiply without needing a host. One can differentiate between bacteria by the shape; these include spherical bacterium or coccus, rod-shaped bacterium or bacillus and spiral bacterium or spirillum. Under a microscope, bacteria look rather strange. They form little balls, flakes, or worm-like squiggles. Yet bacteria are normal phenomena. More than 600 million bacteria live on our skin alone. Under our armpits, 800 bacteria per square millimetre may exist, while drier spots such as the forearm may be occupied by around 20 bacteria per square millimetre.

There are both harmless and harmful bacteria like the streptococci which cause dental caries. Staphylococci types include those that cause conditions as diverse as boils and pneumonia. The most common venereal disease - chlamydia - is also caused by a bacterium, and this is also true of gonorrhoea and syphilis. Generally the body reacts similarly to both a bacterium or a virus: it starts to create antibodies. Bacterial diseases and disorders can usually be treated effectively with antibiotics.

Infectious diseases are diseases you can catch from other people. These infections may be minor, such as a cold, or more serious infections like AIDS and hepatitis. Fortunately, infection is easy to avoid for most infectious diseases.

Some infectious diseases can be transmitted through normal daily contact. By normal daily contact we mean the usual daily interaction with others, such as talking, eating together, touching people, engaging in sports activities or taking communal showers. Influenza and TB are major infectious diseases that can be transmitted through this sort of daily contact.

Some risky situations may arise in the course of daily contact, such as sharing toothbrushes, shaving equipment (esp. razors) and trimming scissors. Blood particles can stick to these items, and when shared with others, these blood particles can be transmitted from one person to another.

Blood-to-blood contact

Other viruses may only be transmitted via blood-to-blood contact, by which we mean that the blood particles of one individual enter somebody else’s bloodstream. This can happen in various ways:

  • Pricking the skin with a needle or syringe with somebody else’s blood on it
  • Blood can also be transmitted through equipment, such as cotton balls
  • Blood entering an open wound or skin with sores and scratches (such as bites)
  • Blood entering the eyes, mouth or nose

These blood particles may not be visible to the naked eye.

The most common risks stemming from blood-to blood contact concern different ways of using drugs. In order to distribute the small quantities of heroin bought fairly between two or more consumers, two different methods are used. The most dangerous form is needle sharing, i.e. injection equipment (consisting of a syringe and/or a needle) is used by two or more consumers. The heroin powder is dissolved in a spoon, then the whole quantity of liquid heroin is drawn up into a single syringe which is then used by the drug consumers in succession. The contents of the syringe can be divided equally by using the scale lines marked on the syringe (a rarely used technique). This practice is still common among drug users, particularly in prisons.

Using several syringes

The other way of sharing drugs is by dividing the heroin between several syringes. The dissolved powder is divided between different syringes to distribute the quantity in equal amounts. This can be done in either of two ways:

  • Front loading
    • The solution is squirted via the tip of the needle into the second syringe in the opening at the front, and then it is injected.
  • Back loading
    • The plunger of the second syringe is removed and the solution of dissolved heroin is passed to the next syringe via the opening at the back. This technique is mostly applied with insulin syringes where the barrel and the needle form a single unit.

These two forms of drugs sharing are only completely safe if all the equipment used is brand new or has been cleaned and sterilized thoroughly.