About Infectious Diseases
diseases are caused by microscopic organisms, including
bacteria, viruses, fungi and animal parasites, that penetrate
the body’s natural barriers and multiply to create symptoms
that can range from mild to deadly.
Although progress has been made in eradication or
control of many infectious diseases, humankind remains
vulnerable to a wide array of new and resurgent diseases.
The problem is complicated by the rapid biological
processes that result in the emergence of new, potentially
dangerous bacteria, viruses, fungi and parasites, many of
which may be resistant to available antibiotics and other
such as population crowding and easy travel also make us more
vulnerable to the spread of infectious agents.
Some infections, such as measles, malaria, typhus and
yellow fever, affect the entire body.
Other infections, however, affect only one organ or
system of the body. The
most frequent local infections, including the common cold,
occur in the upper respiratory tract.
Other common sites of infection include the digestive
tract, the lungs, the reproductive and urinary tracts, and the
eyes and ears. Local
infections can cause serious illnesses if they affect vital
organs such as the heart, brain or liver.
They also can spread through the blood stream to cause
widespread symptoms. The
outcome of any infection depends on the number and virulence
of infectious agents, and the response of the immune system.
A compromised immune system, which can result from
diseases such as AIDS or treatment of diseases such as cancer,
may allow organisms that are ordinarily harmless to
proliferate and cause life-threatening illness.
Common ways in which infectious agents enter the body
are through skin-to-skin contact, inhalation of airborne
microbes, ingestion of contaminated food or water, entry
through broken skin, insect bites, sexual contact, and
transmission from mothers to their unborn children via the
birth canal and placenta.
Modern vaccines are among our most effective strategies
to prevent disease. Many
devastating diseases can now be prevented through aggressive
immunization programs. In the United States, it is recommended that all children be
vaccinated against diphtheria, pertussis (whooping cough),
tetanus, polio, measles, rubella (German measles), mumps,
Haemophilus influenzae type B (a common cause of pneumonia and
meningitis in infants), hepatitis B and varicella
to foreign countries may require vaccinations against yellow
fever, cholera, typhoid fever and hepatitis.
Measures that assure clean water supplies, adequate
sewage treatment, and sanitary handling of food and milk also
are important to control the spread of infectious disease.
The fight against infectious diseases requires
worldwide surveillance by physicians, scientists and public
health officials who gather information on communicable
diseases, report new or resurgent outbreaks of disease, and
develop standards and guidelines for treating and controlling
development of antibiotics and other disease-fighting drugs
has played an important role in the fight against infectious
diseases, but some microorganisms develop resistance to the
drugs used against them.
Modern physicians should prescribe antibiotics
more widely these drugs are used, the more likely it is that
antibiotic-resistant strains of microorganisms will emerge