Popular Science Knowledge

Bacteria are the smallest living things. They are simple organisms that consist of one cell. They exist almost everywhere. They are in the air, water, and soil, as well as in the body of all living creatures. There are thousands of kinds of bacteria. Most of them are harmless to human beings, but some cause diseases such as tuberculosis and pneumonia.

Viruses are also microscopic organisms, but viruses live in the cell of other living things. By themselves, they are lifeless particle that cannot reproduce, but inside a living cell they become active and can multiply hundred of times. Viruses cause many diseases. They infect human beings with such illness as influenza, the common cold, measles, and AIDS(Acquired Immune Deficiency Syndrome).Viruses are tiny. The virus that causes AIDS is so small that 203 million of them could fit on the period at the end of this sentence. Today health official are expressing great concern about our health in the future. They feel that today there is an epidemic of infectious condition that are difficult or impossible to treat, such as AIDS.

In addition to this concern about new life-threatening viral infections, health official have discovered that bacterial infections that were once easily handled by antibiotics now pose a serious threat to our health. Many common bacteria have developed resistance to antibiotics and are evolving into form that are unaffected by all known medications. In a world where antibiotics don't work, the simplest infections are capable of escalating into fatal illness. Every year more people are dying of infections that resist every drug doctors try. The potential ineffectiveness of antibiotics is a frightening prospect.