infarctionDeath of an area of tissue
due to ischaemia (lack of blood supply).
Common examples include myocardial
infarction, which is also known as heart
attack, and pulmonary infarction, which
is lung damage caused by a pulmonary
embolism – a blood clot that has moved
into a vessel in the lung and is obstruct-
ing the flow of blood. (See also necrosis.)
infectionThe establishment in the body
of disease-causing microorganisms (such
as bacteria, viruses, or fungi). The organ-
isms reproduce and cause disease by
direct damage to cells or by releasing
toxins. This normally provokes the im-
mune system into responding, which
accounts for many common symptoms.
Infection can be localized within a par-
ticular area or tissue, as in a boil, or be
systemic (spread throughout the body),
as in influenza. Weakness, aching joints,
and fever are expressions of systemic
infectious disease. Localized infection
may result from the spread of organisms
through wounds, or during surgery. Lo-
calized infection is generally associated
with pain, redness, swelling, and forma-
tion of a pus-filled abscess at the site of
infection, and a rise in temperature.
Many minor infections are dealt with by
the immune system and need no speci-
fic treatment. Severe systemic infections
may need treatment with drugs such as
antibacterialsor antivirals. A localized
infection that has produced pus may be
drained surgically.
infection, congenitalInfection acquired
in the uterus or during birth. Many micro-
organisms can pass from the mother, by
way of the placenta, into the circulation
of the growing fetus. Particularly ser-
ious infections acquired in the uterus
are rubella, syphilis, toxoplasmosis, and
cytomegalovirus; all these infections may
cause intrauterine growth retardation.
Rubella that occurs in early pregnancy
may cause deafness, congenital heart
disease, and eye disorders. Some infec-
tions in later pregnancy, particularly with
a herpesvirus, may alsodamage the
fetus severely. A woman infected with
HIVrisks passing on the virus to her baby
during pregnancy, but the risk can be
reduced by use of antiretroviral drugs
during the pregnancy.Infections acquired during birth are
almost always the result of microorgan-
isms in the mother’s vaginal secretions
or uterine fluid. Premature rupture of the
membranes is associated with increased
risk of infection, particularly streptococ-
cal. Conditions that can be acquired
during delivery include herpes, chlamy-
dial infections, and gonorrhoea.
Treatment of the baby depends on the
type of infection. Some birth defects
caused by infection (such as certain
types of heart defect) can be treated;
others (such as congenital deafness) are
usually not treatable.
infectious diseaseAny illness caused
by a specific microorganism. The most
important disease-causing organisms are
viruses, bacteria, including rickettsiae,
chlamydiae, and mycoplasmas, and fungi.
Others are protozoaand worms.
In developed countries, infectious dis-
eases are generally less of a threat than
in the past because of better methods to
control the spread of disease organisms
(such as better sanitation and water puri-
fication); effective drugs; immunization;
and better general health and nutrition.
For most infectious diseases, there is a
time gap between the entry of the micro-
organisms into the body and the 1st
appearance of symptoms. This incuba-
tion period, during which an infected
person is likely to pass the microorgan-
ism to others, may be a few hours, a few
days, or, in some cases, months.
Antibiotics and other antimicrobial
drugs are the mainstay of treatment for
bacterial infection. For viral infection,
however, drug treatment is restricted to
severe infections.
infectious mononucleosisSee mono-
nucleosis, infectious.
inferiority complexA neurotic state of
mind that develops because of repeated
hurts or failures in the past. Inferiority
complex arises from a conflict between
the positive wish to be recognized as
someone worthwhile and the haunting
fear of frustration and failure. Attempts
to compensate for the sense of worth-
lessness may take the form of
aggression and violence, or an over-
zealous involvement in activities. (See
also superiority complex.)INFARCTION INFERIORITY COMPLEXI