I
HERMAPHRODITISM
MAIN TYPES OF VIRAL HEPATITIS
Viral hepatitis type A
(epidemic hepatitis)
Viral hepatitis types
B and C
Transmission
of infection
The virus is present in the faeces of
infected people and is transmitted by
faecal contamination ofwater and
food (such as through poor hygiene in
food handling). Faeces are infective
from two to three weeks before until
about eight days after the onset of
jaundice. Local epidemics can occur.
These viruses are present in the
blood and other body fluids of infected
people, manyofwhom appear to be
in normal health. Infection is spread
sexually or by sharing hypodermic
needles; in the past itwas spread
by use of contaminated blood and
blood products.
Groups at
particular
risk
Travellers to areas where hygiene
standards are poor and prevalence of
the virus is high (such as parts of
Asia, Africa, or South America) are
most at risk.
Those most at risk are male
homosexuals, people with multiple
sexual partners, intravenous drug
users, healthcare workers, or babies
born to mothers with the virus.
Incubation
period
This lasts for 15-40 days after the
virus has entered the body.
This lasts for i-6months (type B) and
6-12 months (type C) after infection.
Symptoms
and outlook
In many cases there are no
symptoms. There may be nausea,
vomiting, malaise, and a mild flulike
illness with jaundice, lasting about
two to three weeks. The condition
never progresses to chronic hepatitis.
Symptoms are similar to those ofthe
type A virus, although they may be
more severe. Up to ten per cent of
adults with type B and up to 70 per
centwith type C develop chronic
hepatitis, with continuing illness and
eventual cirrhosis ofthe liver.
Preventive
measures
Travellers should take advice about
the need for immunization for travel
to a given destination. Active
immunization involves two doses of
the hepatitis A vaccine, given six to
12 months apart; this provides
immunity for up to ten years.
Measures include the screening of
blood donors, treatment of donated
blood, and safe sex. Intravenous drug
users should not share needles.
Immunization against hepatitis B may
be offered to people at high risk of
contracting the virus (such as babies of
infected mothers, healthcare workers,
and drug users). Travellers should take
advice about the need for immunization
for their destination. The vaccine is
given in three doses; the second dose
is given one month after the first, and
the third six months after the first.
herald patch
A s i n g l e p i n k p a t c h w i t h a s c a l y e d g e
t h a t a p p e a r s o n t h e s k i n o f t h e t r u n k . A
h e r a l d
p a t c h
d e v e l o p s
a b o u t
a
w e e k
b e f o r e t h e f u l l r a s h o f t h e s k i n d i s o r d e r
p i t y r i a s i s r o s e a
b r e a k s o u t .
herbal medicine
S y s t e m s o f m e d i c a l t r e a t m e n t i n w h i c h
v a r i o u s p a r t s o f d i f f e r e n t p l a n t s a r e u s e d
t o p r o m o t e h e a l t h a n d t o t r e a t s y m p t o m s
o f i l l n e s s . H e r b a l m e d i c i n e i s a f o r m o f
c o m p l e m e n t a r y m e d i c i n e
.
H e r b a l r e m e d i e s
a r e a l s o u s e d i n t r e a t m e n t s s u c h a s
h o m e -
o p a t h y
a n d
C h i n e s e m e d i c i n e
.
A l t h o u g h h e r b a l m e d i c i n e i s t h o u g h t
b y s o m e t o b e
h a r m l e s s b e c a u s e i t i s
n a t u r a l , s o m e h e r b a l r e m e d i e s c o n t a i n
s i g n i f i c a n t a m o u n t s o f p h a r m a l o g i c a l l y
a c t i v e s u b s t a n c e s t h a t m a y i n t e r a c t w i t h
o t h e r d r u g s o r a f f e c t o t h e r m e d i c a l c o n -
d i t i o n s . H e r b a l r e m e d i e s s h o u l d o n l y b e
u s e d o n t h e a d v i c e o f a n a p p r o v e d p r a c -
t i t i o n e r ; a p a t i e n t s h o u l d a l w a y s i n f o r m
h i s o r h e r d o c t o r o f a n y h e r b a l m
e d i -
c i n e h e o r s h e i s u s i n g .
herd immunity
P r o t e c t i o n o f a w h o l e c o m m u n i t y f r o m
a n
i n f e c t i o u s
d i s e a s e
a s
a
r e s u l t
o f
i m m u n i t y i n a m a j o r i t y , b u t n o t a l l , o f
t h a t c o m m u n i t y . S u c h i m m u n i t y m a y b e
n a t u r a l l y a c q u i r e d
o r m a y b e
i n d u c e d
b y
i m m u n i z a t i o n
.
F o r e x a m p l e , v a c c i n a -
t i o n
o f m
o r e
t h a n
8 5
p e r
c e n t
o f a
p o p u l a t i o n a g a i n s t d i p h t h e r i a w i l l p r e -
v e n t t h e s p r e a d o f t h e d i s e a s e , s h o u l d i t
o c c u r , d u e t o a n i n s u f f i c i e n t n u m b e r o f
s u s c e p t i b l e
p e o p l e w h o
c o u l d
c a t c h i t
a n d p a s s i t o n t o o t h e r s . A s a r e s u l t , e v e n
t h o s e p e o p l e w i t h o u t i m m u n i t y r e c e i v e
a d e g r e e o f p r o t e c t i o n f r o m b e i n g p a r t
o f a n i m m u n e p o p u l a t i o n .
hereditary haemorrhagic
telangiectasia
A n i n h e r i t e d c o n d i t i o n i n w h i c h c a p i l -
l a r i e s ( t i n y b l o o d v e s s e l s ) i n t h e s k i n a n d
i n t h e m u c o u s m e m b r a n e s o f a r e a s s u c h
a s t h e n o s e , m o u t h , a n d g a s t r o i n t e s t i n a l
t r a c t a r e d i s t e n d e d a n d p r o n e t o r e c u r -
r e n t b l e e d i n g . T h e c o n d i t i o n c a n r e s u l t i n
i r o n
d e f i c i e n c y
a n a e m i a
( s e e
a n a e m i a ,
i r o n d e f i c i e n c y
) . H e r e d i t a r y h a e m o r r h a g i c
t e l a n g i e c t a s i a s h o w s a n a u t o s o m a l d o m i -
n a n t p a t t e r n o f i n h e r i t a n c e ( s e e
g e n e t i c
d i s o r d e r s
) . ( S e e a l s o
t e l a n g i e c t a s i a
. )
hereditary spherocytosis
S e e
s p h e r o c y t o s i s , h e r e d i t a r y .
heredity
T h e t r a n s m i s s i o n o f t r a i t s a n d d i s o r d e r s
t h r o u g h g e n e t i c m e c h a n i s m s . E a c h i n d i -
v i d u a l i n h e r i t s a c o m
b i n a t i o n o f
g e n e s
v i a t h e s p e r m a n d e g g c e l l s f r o m w h i c h
h e
o r
s h e
i s
d e r i v e d . T h e
i n t e r a c t i o n
o f t h e g e n e s d e t e r m i n e s i n h e r i t e d c h a r -
a c t e r i s t i c s ,
i n c l u d i n g ,
i n
s o m e
c a s e s ,
d i s o r d e r s o r s u s c e p t i b i l i t y t o d i s o r d e r s .
( S e e a l s o
g e n e t i c d i s o r d e r s
;
i n h e r i t a n c e
.)
heritability
A
m e a s u r e
o f t h e
e x t e n t
t o
w h i c h
a
d i s e a s e o r d i s o r d e r i s t h e r e s u l t o f i n h e r -
i t e d
f a c t o r s ,
a s
o p p o s e d
t o
e n v i r o n -
m e n t a l i n f l u e n c e s s u c h a s d i e t a n d c l i -
m a t e . C e r t a i n d i s o r d e r s ( s u c h a s
h a e m o -
p h i l i a
o r
c y s t i c f i b r o s i s
)
a r e
k n o w n
t o
b e c a u s e d e n t i r e l y b y h e r e d i t a r y f a c t o r s .
I n c o n t r a s t , o t h e r s a r e c a u s e d w h o l l y b y
e n v i r o n m e n t a l f a c t o r s . H o w e v e r , e x i s t i n g
b e t w e e n t h e s e e x t r e m e s a r e m a n y d i s o r -
d e r s
( s u c h
a s
s c h i z o p h r e n i a
)
i n
w h i c h
b o t h i n h e r i t a n c e a n d e n v i r o n m e n t p r o b -
a b l y p l a y a p a r t .
A r o u g h e s t i m a t e
o f h e r i t a b i l i t y c a n
b e o b t a i n e d f r o m t h e k n o w n i n c i d e n c e
o f a d i s o r d e r i n t h e f i r s t - d e g r e e r e l a t i v e s
( p a r e n t s o r s i b l i n g s )
o f a f f e c t e d p e o p l e
c o m p a r e d w i t h t h e i n c i d e n c e o f t h e d i s -
o r d e r i n a p o p u l a t i o n e x p o s e d t o s i m i l a r
e n v i r o n m e n t a l
i n f l u e n c e s .
E s t i m a t e s
o f
h e r i t a b i l i t y
a r e
u s e f u l
i n
g e n e t i c c o u n -
s e l l i n g
.
( S e e a l s o
g e n e t i c d i s o r d e r s
.)
hermaphroditism
A
c o n g e n i t a l
d i s o r d e r i n w h i c h
g o n a d s
( t e s t e s o r o v a r i e s ) o f b o t h s e x e s a r e p r e -
s e n t
w i t h i n
o n e
i n d i v i d u a l ,
a n d
i n
H
377
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