wart, plantarA hard, horny, and rough-
surfaced area on the sole of the foot
caused by a virus called a papillomavirus.
Plantar warts, also known as verrucas,
may occur singly or in clusters. The wart
is flattened and forced into the skin and
may cause discomfort or pain when
walking. Infection is usually acquired
from contaminated floors in swimming
pools and communal showers.
Many plantar warts disappear without
treatment, but some persist for years or
recur. They can be removed by cryo-
surgeryor by applying plasters or gel
containing salicylic acid.
warts, genitalFleshy, painless, usually
soft lumps that grow in and around the
entrance of the vagina, around the anus,
and on the penis. Genital warts are
transmitted by sexual contact and are
caused by a papillomavirus. There may
be an interval of from a few weeks up to
18 months between time of infection
and the appearance of the warts.
Genital warts have been linked with
the development of cervical cancer (see
cervix, cancer of). They may be removed
by cryosurgeryor by the application of
the drug podophyllin, but there is a ten-
dency for them to recur.
wasp stingsSee insect stings.
waterA simple compound that is essen-
tial forall life. Its molecular structure is
H 2 O (2 atoms of hydrogen bonded to 1
of oxygen). Water is the most common
substance in the body, accounting for
about 99 per cent of all molecules, but
a smaller percentage of total body
weight. Approximately 2 thirds of the
body’s water content is contained with-
in the body cells, and the remaining
third is extracellular (found, for example,
in the blood plasma, lymph, and cere-
brospinaland tissue fluid).
Water provides the medium in which
all metabolic reactions take place (see
metabolism), and transports substances
around the body. The blood plasma car-
ries water to all body tissues, and excess
water from tissues for elimination via
the liver, kidneys, lungs,and skin. The
passage of water in the tissue fluid into
and out of cells takes place by osmosis.
Water is taken into the body in food
and drink and is lost in urineand faeces,as exhaled water vapour, and by sweat-
ing (see dehydration). The amount of
water excreted in urine is regulated by
the kidneys (see also ADH). Extra water
is needed to excrete excess amounts of
substances, such as sugar or salt, in the
blood, and high water intake is essen-
tial in hot climates where a large amount
of water is lost in sweat.
In some disorders, such as kidney fail-
ureor heart failure, insufficient water is
excreted in the urine, resulting in oedema.
water-borne infectionA disease caus-
ed by infective or parasitic organisms
transmitted via water. Infections can be
contracted if infected water is drunk, if
it contaminates food, or if individuals
swim or wade in it. Worldwide, contami-
nation of drinking water is an important
mode of transmission for various dis-
eases including hepatitis A, many viral
and bacterial causes of diarrhoea, typhoid
fever, cholera, amoebiasis, and some
types of worm infestation.
Swimming in polluted water should
be avoided because, if swallowed, there
is a risk of contracting disease. In addi-
tion, a form of leptospirosisis caused
by contact with water contaminated by
rat’s urine. In tropical countries, there is
also a risk of contracting schistosomiasis
(bilharzia), which is a serious disease
caused by a fluke that can burrow through
the swimmer’s skin.
waterbrashThe sudden filling of the
mouth with tasteless saliva. It is not to
be confused with acid reflux(the regur-
gitation of gastric juices), which has an
unpleasant, sour taste. Waterbrash is
normally accompanied by other symp-
toms, and usually indicates a disorder
of the upper gastrointestinal tract.
Waterhouse–Friderichsen syndrome
A serious condition caused by infection
of the bloodstream by bacteria of the
meningococcus group. The main features
are bleeding into the skin, low blood
pressure, and shock. Without urgent
medical treatment, coma and death fol-
low in a few hours. The syndrome is
often associated with meningitis.
watering eyeAn increase in volume of
the tear film, usually producing epiph-
ora (overflow of tears). Watering may
be caused by excess tear productionWART, PLANTAR WATERING EYEW