Hepatitis
INTRODUCTION
Hepatitis,
inflammation of the liver, usually due to acute viral infection. It occurs in
several forms. Lifelong immunity to the causative virus usually follows an
attack, but since several distinct viruses cause the disease—at least five are
now known—immunity to one type does not confer immunity to the others.
HEPATITIS A
Previously known
as infectious hepatitis, hepatitis A is caused mainly by poor sanitation and
lack of hygiene. It is transmitted by food or water contaminated by excreta; by
other objects taken into the mouth; from person to person, including by sexual
contact; or by injection with improperly sterilized hypodermic needles or
needles shared by intravenous (IV) drug users. Outbreaks often occur in army or
refugee camps and in institutions where small children are crowded together.
Shellfish and uncooked food carry risk of infection. This form of the disease
has become more common as a result of increased travel to countries where
hepatitis A is common and where clean water and proper sewage disposal are not
available. Hepatitis A is usually less severe than hepatitis B and patients
generally recover within weeks, whereas hepatitis B can last for months.
HEPATITIS B
Previously called
serum hepatitis, hepatitis B can be transmitted by intimate sexual contact, as
well as from a mother to a foetus or newborn baby. Hepatitis B is also
transmitted by injections transporting a virus-bearing serum, most often during
blood transfusion, by contaminated needles and syringes used medically or for
injecting drugs, and by acupuncture or tattooing. The virus is also present in
other body fluids, such as semen, vaginal fluid, saliva, and tears.
Hepatitis B can cause lifelong infection and lead to cirrhosis
(scarring) of the liver, liver cancer, and liver failure. It causes more than
250,000 deaths each year worldwide with the highest incidence in Africa,
south-eastern Asia, Alaska, China, and the Amazon. In 1993 there were under
1,000 cases reported in the United Kingdom which, compared with the 1984 figure
of 3,000, represents a decline—although many cases go unreported.
In 1965 Baruch Samuel Blumberg, an American research scientist,
identified a viral component (known as the Australia antigen) that determines
whether a sample of blood can transmit hepatitis B. All samples of blood
intended for transfusion are now routinely tested for the antigen; this has
greatly reduced the incidence of post-transfusion hepatitis.
In 1977 an Italian doctor, Mario Rizzetto, identified a virus—now
called the delta hepatitis virus—that cannot replicate on its own and requires
the presence of the hepatitis-B virus to be transmitted. The delta virus occurs
worldwide and has caused major epidemics; this form of the disease, sometimes
called hepatitis D, can also become chronic and lead to liver failure.
HEPATITIS C, E,
AND G
Three more types
of hepatitis have also been identified. Also known as non-A, non-B hepatitis,
hepatitis C is mainly transmitted by infected blood and blood products, by
contaminated syringes, or less commonly, in body fluids through sexual contact.
It is caused by a virus that has now been cloned, and is the most common cause
of post-transfusion hepatitis. About half of hepatitis C sufferers may suffer
persistent infection. There is no vaccine available.
Hepatitis E is, like hepatitis A, transmitted in contaminated
drinking water and can cause an epidemic form of the disease in tropical areas.
There is no vaccine available. Hepatitis G virus is blood-borne; groups at risk
include IV drug users and those who have been infected frequently with hepatitis
C virus.
SYMPTOMS
Symptoms of all
forms begin with fever, usually followed by extreme weakness, loss of appetite,
nausea, vomiting, and muscle pains. The upper abdomen may be painful and tender.
Jaundice (yellowing of the skin and whites of eyes) appears gradually, reaching
maximum intensity at two weeks. Convalescence may take up to six months.
Hepatitis C, however, may be without symptoms. In about 5 per cent of victims
the disease goes on to a chronic form. The fatality rate from all types of
hepatitis is about 1 per cent but may be higher for hepatitis B, especially when
co-infection by delta virus is also present.
PREVENTION AND
TREATMENT
A
Hepatitis A
Vaccines
made from inactivated hepatitis A viruses provide long-term protection against
hepatitis A and are recommended prior to travelling to a large number of
countries; two doses of the vaccine are usually administered. Hepatitis
immunoglobulin (HBIG), a preparation of antibodies (passive immunization), is
sometimes used for short-term protection against hepatitis A and for people who
have already been exposed. It has to be given within two weeks of exposure for
maximum protection.
Hepatitis B
Avoidance
of risk behaviour and immunization of groups most at risk are the main
preventive measures against hepatitis B. An effective vaccine that prevents
hepatitis B is available to groups at risk, from, for example, GUM
(genital-urinary medicine) clinics. Although its use has remained limited
because of its cost, it is recommended for health-care workers, sexually active
homosexual men, and others who may be exposed to blood that may contain the
virus. This genetically engineered hepatitis B vaccine is used as active
immunization (that is, containing a form of the infectious micro-organism to
stimulate antibodies) and is effective for up to five years. It is usually given
as a series of two to three injections over a period of two months, after which
blood antibody levels are checked. In addition to this preventive treatment HBIG
is used as passive immunization vaccine following exposure and is usually
administered in combination with hepatitis B vaccine. For a person who has been
accidentally stuck by a needle contaminated with the virus, administration of
HBIG greatly reduces the chance of developing the illness. HBIG must be given no
later than a week following exposure.
Recombinant alpha interferon, a naturally occurring antiviral
substance now marketed as a genetically engineered drug, has been effective in
treating many patients with chronic hepatitis C and some patients with chronic
hepatitis B. No treatment is available for acute viral hepatitis.