Before the 17th century, the smallest living creatures anyone knew anything about were the insects. Then along came Anton van Leeuwenhoek and his microscope, and suddenly a whole new world of microorganisms was discovered.
It was Louis Pasteur who first connected these microorganisms with disease - through studies he was doing on silkworms. These disease-causing microscopic creatures, called pathogens, take over some of the body's cells and tissues and use them for their own growth and reproduction, thus damaging or destroying the cells and producing the disease.Although fungi, protozoans and worms can cause diseases, the most common pathogens are bacteria and viruses.
One-celled bacteria rank among the most widespread of all living things. A single grain of soil may contain more than 100 million bacteria. Not all are harmful. Many kinds of bacteria live in the human mouth or intestines or on the skin and seldom cause problems unless they are moved to an organ where they are not normally present. (For example, bacteria that are harmless in the mouth can cause problems in the middle ear.) Most bacterial diseases, such as bacterial pneumonia, gonorrhea and tuberculosis, result when bacteria multiply rapidly in living tissue damaging or killing it. Some bacteria produce toxins harmful to tissues, as in tetanus and botulism.
Viruses are smaller than bacteria, and like bacteria, they are parasites, invading a cell and using the cell's materials to reproduce and grow. Many common diseases, including chicken pox, German measles, measles and mumps, are caused by viruses, which are also responsible for colds, flu and most cases of diarrhea and vomiting.
The way these pathogens spread was not understood until the mid-1800s, when a Hungarian obstetrician named Ignaz Semmelweiss, studying the rates of death from childbed fever in a maternity hospital, realized that the germs were spread when medical personnel came in contact with infected materials. This led Semmelweiss to require all medical students and physicians to wash their hands in chlorinated solutions before delivering babies. It proved to be the determining factor in reducing the death rates in the hospital.
Today we know that germs are spread both by direct and by indirect contact. Hands are the most common spreader of germs. Because they are often warm and moist, hands provide a perfect environment for germs to live. And, because hands are constantly touching things, they pick up germs as well as spread them.
However, the role of surfaces is becoming understood more completely. Studies have shown that the germs that cause respiratory (rhinovirus) and intestinal (rotavirus) illnesses are very effectively transferred from contaminated surfaces to the hand, which then touches the mouth, nose or eyes and transfers the germs to the body. One 1988 study found that you are more likely to pick up viruses from touching contaminated surfaces than from shaking the hand of someone who is infected.
Scientists are also finding that germs can live longer than expected on surfaces. They are finding that most of these germs can live up to three days on moist surfaces, such as tissues, glass or stuffed animals. If the surface remains moist, some germs can live indefinitely. Researchers have also been surprised to find that the rhinovirus can even survive for an hour on a dry surface, such as a pencil, toy or playing card.
They are also finding that only a few viruses are needed to cause an infection. Ingestion of only one to 10 rhinoviruses, for example, are needed to cause diarrhea in healthy adults.
Certain places seem to be hotbeds for spreading diseases and infections.
Child care settings are especially vulnerable. Young children's immune systems are not yet fully developed, and they are coming into contact with new germs for the first time, so the risk of becoming ill is greatly increased. According to a 1990 study cited by the Soap and Detergent Association, a child in group care has at least a 30 percent greater chance of getting diarrhea than a child taken care of at home.
Offices also are high on the list. Using the phone after a co-worker has coughed or sneezed into it can spread rhinovirus from one worker to the other; materials that are touched by an infected person are passed on to another.
But the good news is that many common-sense precautions can help stop the spread of germs. We often fail to protect others from our germs. Covering our mouths when we cough and sneeze can reduce the spread of germs. Taking special precautions with the bedside area when an ill individual is recuperating - such as a night stand or container where tissues are discarded - can help.
Other simple suggestions from the Soap and Detergent Association:
- Maintain a clean environment, including clothes, bedding, dishes and other items that are shared by others.
- When you do have an infectious condition, try to stay away from others and especially avoid touching them.
- Frequent hand-washing is as vital today as it was in Semmelweiss' time to stop the chain of transmission of infections.
You can't completely rid your home of germs, but with proper cleaning and disinfection and other common-sense cleanliness habits, you can help reduce the effect that germs have on you and your family's health.
*****
ADDITIONAL INFORMATION
Some communicable diseases
Disease Period of communicability
AIDS Immediately after infection and as long as virus remains
in body.
Chickenpox From 1 to 2 days before symptoms appear until 6 days
after first rashes form.
German measles Immediately after infection and as long as virus remains
(Rubella) in body.
Influenza When symptoms appear until 7 days after.
Measles From 4 days before rash appears until 5 days after.
Mononucleosis Unknown.
Mumps From 7 days befor until 9 days after symptoms, or until
swelling disappears.
Poliomyelitis Last part of incubation period and first week of acute
illness.
Scarlet fever Beginning of incubation period until 2 or 3 weeks after
symptoms appear.