DESECRIPTION
Infectious Agent:All types of VH are caused by RNA virus except HBV, which is caused by DNA virus
.
Water-related Diseases:
Hepatitis, a broad term for inflammation of the liver, has a number ofinfectious and non-infectious causes. Two of the viruses that cause hepatitis
(hepatitis A and E) can be transmitted through water and food; hygiene is
therefore important in their control.
The disease and how it affects people
Among the infectious causes, hepatitis A and hepatitis E are associated with
inadequate water supplies and poor sanitation and hygiene, leading to infection
and inflammation of the liver. The illness starts with an abrupt onset of fever,
body weakness, loss of appetite, nausea and abdominal discomfort, followed by
jaundice within a few days.
The disease may range from mild (lasting 1-2 weeks) to severe
disabling disease (lasting several months). In areas highly endemic for
hepatitis A, most infections occur during early childhood. The majority of cases
may not show any symptoms; fatal cases due to fulminant acute hepatitis are
rare. Nearly all patients recover completely with no long-term effects.
The cause:
Hepatitis A and E viruses, while unrelated to one another, are both transmitted
via the fecal-oral route, most often through contaminated water and from person
to person. Hepatitis A could also be transmitted via food contaminated by
infected food-handlers, uncooked foods, or foods handled after cooking.
Hepatitis A has also caused outbreaks transmitted through injecting or
non-injecting drug use.
Distribution
Both hepatitis A and E are found worldwide. Hepatitis A is particularly frequent
in countries with poor sanitary and hygienic conditions (in Africa, Asia, and
Central and South America). Countries with economies in transition and some
regions of industrialized countries where sanitary conditions are sub-standard
are also highly affected, e.g.in southern and eastern Europe and some parts of
the Middle East. Outbreaks of hepatitis E have occurred in Algeria, Bangladesh,
China, Ethiopia, Indonesia, Iran, Libyan, Mexico, Nepal, Pakistan, Somalia .
Scope of the Problem
The mortality rate is low (0.2% of icteric cases) and the disease ultimately
resolves. Occasionally, extensive necrosis of the liver occurs during the first
6-8 weeks of illness. In such cases, high fever, marked abdominal pain,
vomiting, jaundice, and hepatic encephalopathy (with coma and seizures) are the
signs of fulminant hepatitis, leading to death in 70-90% of the patients. In
these cases mortality is highly correlated with increasing age, and survival is
uncommon over 50 years of age. Among patients with chronic hepatitis B or C or
underlying liver disease, who are super infected with hepatitis A virus, the
mortality rate increases considerably.
Improved economic and sanitary conditions may lead to a higher disease incidence
in older age groups, with higher reported rates of clinically evident hepatitis
A. In countries with very low hepatitis A infection rates, the disease may occur
among specific risk groups such as travelers.
Hepatitis E: is mainly found in young to middle-aged adults. Women in the
third trimester of pregnancy are especially susceptible to acute fulminant
hepatitis arising from hepatitis E infection.
Symptoms can return over the following 6–9 months and include:
Fatigue ,Fever, Abdominal pain ,Nausea ,Diarrhea ,Appetite loss ,Depression
,Jaundice, Sharp pains in the right-upper quadrant of the abdomen ,Weight loss
,Itching
Bile is removed from blood stream and excreted in urine giving a dark amber
color
Feces tend to be light in color due to lack of bilirubin in bile
Strong aversion to cigarette smoking
Pathogenesis
Following ingestion, HAV enters the bloodstream through the epithelium of the
oropharynx or intestine. The blood carries the virus to its target, the liver,
and multiplies within hepatocytes and Kupffer cells (liver macrophages).
Virions are secreted into the bile and released in stool. HAV is excreted in
large quantities approximately 11 days prior to appearance of symptoms or
anti-HAV IgM antibodies in the blood.
The incubation period is 15–50 days and mortality is less than 0.5%.
Diagnosis
Serum IgG, IgM and ALT following Hepatitis A virus infection
Although HAV is excreted in the feces towards the end of the incubation period,
specific diagnosis is made by the detection of HAV-specific IgM antibodies in
the blood. IgM antibody is only present in the blood following an acute
hepatitis A infection. It is detectable from one to two weeks after the initial
infection and persists for up to 14 weeks.
The presence of IgG antibody in the blood means that the acute stage of the
illness is past and the person is immune to further infection. IgG antibody to
HAV is also found in the blood following vaccination and tests for immunity to
the virus are based on the detection of this antibody.
During the acute stage of the infection, the liver enzyme alanine transferase
(ALT) is present in the blood at levels much higher than is normal. The enzyme
comes from the liver cells that have been damaged by the virus.
Hepatitis A virus is present in the blood, (viremia), and feces of infected
people up to two weeks before clinical illness develops.
Treatment
There is no specific treatment for hepatitis A. Sufferers are advised to rest,
avoid fatty foods and alcohol (these may be poorly tolerated for some additional
months during the recovery phase and cause minor relapses), eat a well-balanced
diet, and stay hydrated. Approximately 6–10% of people diagnosed with
hepatitis A may experience one or more symptomatic relapse(s) for up to 40 weeks
after contracting this disease.
Prognosis
The United States Centers for Disease Control and Prevention (CDC) in 1991
reported a low mortality rate for hepatitis A of 4 deaths per 1000 cases for the
general population but a higher rate of 17.5 per 1000 in those aged 50 and over.
Death usually occurs when the patient contracts Hepatitis A while already
suffering from another form of Hepatitis, such as Hepatitis B or Hepatitis C
Hepatitis E is a viral hepatitis (liver inflammation) caused by infection with a
virus called hepatitis E virus (HEV). HEV is a positive-sense single-stranded
RNA virus. HEV has a fecal-oral transmission route. Infection with this virus
was first documented in 1955 during an outbreak in New Delhi, India
Epidemiology
The incidence of hepatitis E is highest in juveniles and adults between the ages
of 15 and 40. Though children often contract this infection as well, they less
frequently become symptomatic. Mortality rates are generally low, for Hepatitis
E is a «self-limiting» disease, in that it usually goes away by itself and the
patient recovers. However, during the duration of the infection (usually several
weeks), the disease severely impairs a person’s ability to work, care for
family members, and obtain food. Hepatitis E occasionally develops into an acute
severe liver disease, and is fatal in about 2% of all cases
Clinically, it is comparable to hepatitis A, but in pregnant women the disease
is more often severe and is associated with a clinical syndrome called fulminant
hepatic failure. Pregnant women, especially those in the third trimester, suffer
an elevated mortality rate from the disease of around 20%.
Although there is one serotype of this virus, four distinct genotypes have been
reported. Genotypes 1 and 2 are restricted to humans and often associated with
large outbreaks and epidemics in developing countries with poor sanitation
conditions. Genotypes 3 and 4 infect humans, pigs and other animal species and
have been responsible for sporadic cases of hepatitis E in both developing and
industrialized countries.
Patterns
Hepatitis E is prevalent in most developing countries, and common in any country
with a hot climate. It is widespread in Southeast Asia, northern and central
Africa, India, and Central America. It is spread mainly through fecal
contamination of water supplies or food; person-to-person transmission is
uncommon. Outbreaks of epidemic Hepatitis E most commonly occur after heavy
rainfalls and monsoons because of their disruption of water supplies. Major
outbreaks have occurred in New Delhi, India (30,000 cases in 1955-1956), Burma
(20,000 cases in 1976-1977), Kashmir, India (52,000 cases in 1978), Kanpur,
India (79,000 cases in 1991), and China (100,000 cases between 1986 and 1988).
Prevention
Improving sanitation is the most important measure, which consists of proper
treatment and disposal of human waste, higher standards for public water
supplies, improved personal hygiene procedures and sanitary food preparation.
Thus, prevention strategies of this disease require large-scale international
financing of water supply and water treatment projects. A vaccine based on
recombinant viral proteins has been developed and recently tested in a high-risk
population (military personnel of a developing country). The vaccine appeared to
be effective and safe, but further studies are needed to assess the long-term
protection and the cost-effectiveness of hepatitis E vaccination.
In Iraq 2005- 2006 :
Hepatitis A: is hyper-endemic in Iraq, with no gender differences. Serologic
evidence of previous exposure to the infective agent is present in the majority
of general population (96.4%). It is a disease of childhood. After the second
decade of life no obvious increase in its prevalence is noticed.
. Hepatitis E: is endemic in Iraq with a prevalence of its serologic marker (IgG
antibody) of 20.3%. Males have a slightly higher prevalence rate. A steady
increase in prevalence is observed with advancing age.
Hepatitis A vaccines
Techniques for growing HAV in cell culture have made it possible to generate
sufficient amounts of virus for vaccine production. Several inactivated or live
attenuated vaccines against hepatitis A have been developed, but only four
inactivated hepatitis A vaccines are currently available internationally. All
four vaccines are similar in terms of efficacy and side-effect profile. The
vaccines are given parenterally, as a two-dose series, 6-18 months apart. The
dose of vaccine, vaccination schedule, ages for which the vaccine is licensed,
and whether there is a pediatric and adult formulation varies from manufacturer
to manufacturer. No vaccine is licensed for children younger than one year of
age.
A combination vaccine containing inactivated hepatitis A and recombinant
hepatitis B vaccines has been licensed since 1996 for use in children aged one
year or older in several countries. The combination vaccine is given as a
three-dose series, using a 0, 1, 6 month schedule.
Hepatitis A vaccines are all highly immunogenic. Nearly 100% of adults will
develop protective levels of antibody within one month after a single dose of
vaccine. Similar results are obtained with children and adolescents in both
developing and developed countries.