Human Disease
/ human deases books
Human Disease, in medicine, any harmful
change that interferes with the normal appearance, structure, or
function of the body or any of its parts. Since time immemorial,
disease has played a role in the history of societies. It has affected-and
been affected by-economic conditions, wars, and natural disasters.
Indeed, the impact of disease can be far greater than better-known
calamities. An epidemic of influenza that swept the globe in 1918
killed between 20 million and 40 million people. Within a few months,
more than 500,000 Americans died-more than were killed during World
War I (1914-1918), World War II (1939-1945), the Korean War (1950-1953),
and the Vietnam War (1959-1975) combined.
Diseases have diverse causes, which can be classified into two broad
groups: infectious and noninfectious. Infectious diseases can spread
from one person to another and are caused by microscopic organisms
that invade the body. Noninfectious diseases are not communicated
from person to person and do not have, or are not known to involve,
infectious agents. Some diseases, such as the common cold, are acute,
coming on suddenly and lasting for no more than a few weeks. Other
diseases, such as arthritis, are chronic, persisting for months
or years, or recurring frequently.
Every disease has certain characteristic effects on the body. Some
of these effects, called symptoms and signs, include fever, inflammation,
pain, fatigue, dizziness, nausea, and rashes, and are readily apparent
to the patient. These symptoms offer important clues that help physicians
and other health care professionals make a diagnosis. Many times,
however, the symptoms point to several possible disorders. In those
cases, doctors rely on medical tests, such as blood examinations
and X rays, to confirm the diagnosis.
The course of a disease-that is, the path it follows from onset
to end-can vary tremendously, depending largely on the individual
and the treatment he or she receives. For example, otherwise healthy
people usually recover quickly from a bout of pneumonia if given
proper treatment, whereas pneumonia often proves fatal to people
with a weakened immune system and to those who do not receive prompt,
effective treatment. Some diseases run a different course depending
on the patient’s age. Chicken pox, for instance, is usually
mild in childhood but severe in adults. In the United States, only
about 5 percent of chicken pox cases occur in people over the age
of 20, but these cases account for 50 percent of all deaths from
the disease
Scientists, public health officials, and other members of the medical
community work diligently to try to prevent disease epidemics. The
battle is constant and is fought on many fronts. There have been
many victories. Once-devastating diseases such as smallpox and diphtheria
have been virtually eradicated, and many other diseases that once
conferred automatic death sentences can now be either cured or controlled.
At the same time, however, new killers have emerged. Acquired immunodeficiency
syndrome (AIDS) and hantavirus pulmonary syndrome are among at least
30 diseases that have been identified by scientists since the early
1970s. Other growing challenges, particularly in the affluent societies
of industrialized nations, are so-called diseases of choice, such
as alcohol abuse, drug abuse, or obesity, that result from addictive
behavior, poor eating habits, or insufficient exercise.
Complicating matters further are societal changes. Increased international
travel accelerates the spread of both new and old diseases: A person
infected with an unusual virus on one continent can arrive-with
the virus-on another continent in a matter of hours. Ships, planes,
and trucks can transport disease-carrying organisms just as easily.
In 1985 tires imported into Texas from Asia carried larvae of the
Asian tiger mosquito, which is a carrier of dengue fever and other
tropical diseases. Within five years, Asian tiger mosquitoes were
living in 17 states. Changing dietary habits and the availability
in local supermarkets of foods from all parts of the world contribute
to an increase in food-borne illnesses. Some researchers worry that
growing populations and the resulting crowded living conditions
will increase the risk of epidemics
|
