A disease is something that upsets the normal working of any living thing. It happens when all or
part of the body is not working correctly. It can be acute (sudden, but short-lived), chronic (long-lasting), malignant (dangerous) or benign (harmless). Some diseases are classified by the body part they affect (such as heart disease), or by the body activity they affect (such as respiratory, or breathing, disease). Yet some other diseases are classified by their cause. These include the diseases caused by the staphylococcus bacteria, such as pneumonia.
Diseases can be either infectious (able to be passed on) or noninfectious. Infectious diseases are
spread by germs such as bacteria and viruses. They include smallpox, polio, flu and measles. Their
spread can be controlled by good sanitation and hygiene, and by vaccination programmes.
Non-infectious diseases may be inherited or they may be caused by such things as eating harmful
substances, poor nutrition or hygiene, getting old or being injured. Endemic diseases are diseases
that occur in a particular area of the world, such as sleeping sickness in Africa. Cancer is a disease
in which malignant cells multiply abnormally, creating growths called tumors.
Germs and diseases
Germs are organisms (living things) that are so small they can only be seen through a microscope
They include viruses, bacteria and fungi.Viruses cause the common cold, influenza (flu), measles,
mumps, chicken-pox and other diseases in humans, foot-and mouth disease in cattle, and mosaic disease, which destroys the leaves of many crop plants.
Bacteria, like viruses, are everywhere around us. They cause several diseases, including food poisoning, whooping cough and tuberculosis (TB) in humans, tetanus (lockjaw) in humans and cattle, and canker in fruit trees.
Fungi cause athlete’s foot, thrush and ringworm in humans, as well as some serious internal
infections. They also cause foot rot in cattle, and many serious plant diseases.
Germs are spread in many different ways. They may be breathed in from the air, or they
can be passed by touch. Germs can easily get into food if it is not prepared or stored in a hygienic
(clean) way. Flies and pets can pass germs into food. Insects such as fleas and mosquitoes may
spread germs when they bite the skin. Germs can get into the body through wounds if they are not
cleaned properly.
Diet and disease
A diet containing vitamins and minerals is essential for good health. Vitamin C, for example, is
needed for healthy blood vessels, skin and gums. The mineral calcium helps bones and teeth,
and iron keeps the blood healthy. Heart disease can be caused by eating too much fat, tooth decay by too much sugar, and too much salt can cause high blood pressure.
Developmental diseases
Sometimes, as a baby is growing inside its mother, parts of its body are not formed properly. The
heart, for instance, may grow with a hole between its right and left sides so that the blood does not
flow correctly.
Inherited diseases
These are passed from parents to their young. The offspring are born with them and cannot be
cured, but treatment can often lessen the harmful effects. An example is haemophilia, in
which the blood clots very slowly.
Mental diseases
These are problems of the mind. They show themselves as unusual behaviour, or by great unhappiness (depression). Mental diseases are treated by doctors called psychiatrists.
Preventing disease
Preventing disease is better than having to cure disease. Infection can be reduced by a healthy way
of life. This includes keeping yourself clean, caring for your teeth, eating a healthy diet, controlling
your weight, not smoking or taking drugs or drinking alcohol, and by taking regular exercise.
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