Diseases Essay Research Paper Diseases are any

Diseases Essay, Research Paper

Diseases are 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 has been affected by economic

conditions, wars, and natural disasters. 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: communicable and noncommunicable. Communicable

diseases can spread from one person to another and are caused by

microscopic organisms that invade the body. Noncommunicable 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, and come on suddenly and last for no more than a few weeks. Other

diseases, such as arthritis, are chronic, consistent for months or

years, or reoccur frequently.

Every disease has certain characteristic effects on the body.

Some of these effects, include fever, inflammation, pain,

fatigue, dizziness, nausea, and rashes, are evident to the patient.

These symptoms offer important clues that help doctors and other health

care professionals make a diagnosis. Many times, 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.

Communicable diseases are caused by microscopic organisms.

Physicians refer to these disease-causing organisms as

pathogens. Pathogens that infect humans include a wide variety of

bacteria, viruses, fungi, protozoans, and parasitic worms. Also, it

has been theorized that some proteins called prions may cause

infectious diseases.

Bacteria are microscopic single-celled organisms at least 1

micron long. Some bacteria species are harmless to humans, many

are beneficial. But some are pathogens, including those that cause

cholera, diphtheria, leprosy, plague, pneumonia, strep throat, tetanus,

tuberculosis, and typhoid fever. The bacteria that are harmless and

live in or on you are called resident bateria.

Viruses are tens or hundreds of times smaller than bacteria.

They are not cellular, but consist of a core of genetic

material surrounded by a protective coat of protein. Viruses are able

to survive and reproduce only in the living cells of a host. Once a

virus invades a living cell, it directs the cell to make new virus

particles. These new viruses are released into the surrounding tissues,

and seek out new cells to infect. The roll call of human diseases

caused by viruses includes mumps, measles, influenza, rabies,

hepatitis, poliomyelitis, smallpox, AIDS, and certain types of cancer.

Fungi are a varied group of generally small organisms that get

their food from living or dead organic matter. They germinate

from reproductive cells called spores, which often have a thick,

resistant outer coat that protects against unfavorable environmental

conditions. This enables spores to survive for long periods of time,

which adds to the difficulty of treating fungal infections. Some fungi

are external parasites of humans, causing skin conditions such as

ringworm, athlete’s foot, and jock itch. Other fungi invade internal

tissues. Examples include yeast that infect the genital tract and

several fungi species that cause a type of pneumonia.

Protozoans are single-celled, animal-like organisms that live

in moist environments. The most infamous pathogenic protozoans

are species of the genus Plasmodium, which cause malaria, an infectious

disease responsible for over 2 million deaths worldwide each year.

Members of the genus Trypanosoma produce trypanosomiasis, also known as

African sleeping sickness, and Chagas’ disease. Other protozoans cause

giardiasis, leishmaniasis, and toxoplasmosis.

Some pathogens are spread from one person to another by direct

contact. They leave the first person through body openings,

mucous membranes, and skin wounds, and they enter the second person

through similar channels. The viruses that cause respiratory diseases

such as influenza and the common cold are spread in moisture droplets

when an infected person coughs or sneezes. A hand that was used to

cover the mouth while coughing contains viruses that may be passed to

doorknobs, so that the next person to touch the doorknob has a chance

of picking up the infectious agent. The bacteria that cause some

sexually transmitted diseases, including gonorrhea and syphilis, a

Внимание, отключите Adblock

Вы посетили наш сайт со включенным блокировщиком рекламы!
Ссылка для скачивания станет доступной сразу после отключения Adblock!

Скачать