UNSW. Australia: School students in Victoria, South Australia, and Queensland are
the latest group thought to have eaten frozen berries linked to
hepatitis A, which has now infected 14 people nationally. All food-borne
disease outbreaks are frightening, but the good news for this one is
that hepatitis A is rarely life-threatening.
Hepatitis is
inflammation of the liver and can result from a viral infection by one
of five hepatitis viruses, which are called hepatitis A, B, C, D and E
viruses. The viruses are unrelated to each other but are joined in name
because they all replicate in the liver.
Hepatitis A and E viruses
are probably the least serious, although infection is still harmful. On
average, the blood-borne hepatitis viruses, namely B, C and D are
nastier, mainly because all three can evade the immune system and cause a
life-long infections. This can result in continual liver damage over
decades.
Hepatitis A infection
When someone
is infected by the hepatitis A virus they won’t become ill until two to
seven weeks later. And they’re infectious around two weeks before and
after symptoms.
The infected person will usually experience
general “hepatitis” symptoms (tired, feeling sick, muscle aches, fever)
for up to two weeks before they start to appear yellowish or jaundiced,
as a result of liver damage. Jaundice lasts for between one and three
weeks.
Infection could lead to the liver being enlarged so the
upper right-hand side of the body may feel tender. Even after the
jaundice has faded, hepatitis A infection can leave a patient feeling
tired, off their food and weak for some weeks, or even months.
The
idea of all viruses is to replicate to enormous numbers so they can be
transmitted to new hosts. Hepatitis is no different, and about ten
billion hepatitis A viruses are excreted per gram of feces. That’s why
washing your hands is so important once you’re infected. It only takes
about 1,000 viruses to infect someone – you can do the maths.
The
hepatitis A virus is very common in developing countries, where human
fecal waste often contaminates food and water supplies because
sanitation standards are much lower. But in developed countries, such as
Australia, the United States and the United Kingdom, infection with
hepatitis A is quite rare; few people encounter the virus unless they
travel overseas. This disparity in infection rates between wealthy and
poor countries highlights the need for, and should strengthen efforts
to, generate clean water supplies.
Like most viral infections,
adults fare worse than children. A third of infected adults will get
sick from hepatitis A, so the disease tends to be nastier in Western
countries where mainly adult infections occur.
Only hepatitis A
virus and hepatitis E virus are transmitted through the consumption of
food and water contaminated with human feces. The other three are
transmitted sexually (hepatitis B) or transmitted through virus
contaminated blood (hepatitis B, C, and D).
Other hepatitis viruses
Infection
with any of the five hepatitis viruses generally causes similar
clinical symptoms, which include fever, headache, feeling weak, muscle
aches, and loss of appetite, among other things. But infection with the
hepatitis A virus is different from hepatitis B, C and D viruses because
it seldom results illness lasting for more than a couple of months. In
the vast majority of cases, the virus is eliminated from the body and
the liver totally recovers.
The story is however different for
hepatitis B, C ands D viruses, which can cause lifelong (chronic)
infections in some infected people. A chronic infection is when the
virus remains permanently in the liver because it cannot be removed by
the immune system.
The immune system continually attacks the liver
cells where the virus hides, resulting in their destruction and
ultimately a reduction in the capacity of the liver to do its many
tasks. This means liver damage continues over ten to 20 years and can
lead to serious liver disease and liver cancer. This happens in about a
quarter of those infected with these viruses.
Along with hepatitis
A, hepatitis E also does not cause chronic infection. Having said that,
hepatitis E is very dangerous to pregnant women and can be fatal to
both mother and offspring.
Vaccine and treatment
Vaccines
can protect against hepatitis A and hepatitis B infection, but they
don’t cure infection. Since 1988, all Australian babies get hepatitis B
vaccinations. But as the hepatitis A virus is rare in developed
countries and not life threatening, vaccination is largely offered to
people travelling to places where the virus is endemic. This makes very
good practical sense and it’s cost effective
You should have the
vaccine about a month before you travel because it takes between two and
four weeks for full immune protection, which lasts about 25 years. Just
like mumps and measles, once you’ve had a hepatitis A infection or the
vaccine, you’ll probably be immune for life.
Our main weapon
against hepatitis A virus are immunoglobulins, antibodies that bind to
the virus to prevent further infection of cells. It needs to be
administered two weeks after exposure to be effective. Other than this
there are no real antiviral treatment options for hepatitis A. People
with the virus are clinically supported with management of complications
if they arise.
Treatments can suppress hepatitis B virus
replication, but stopping it will allow the virus to come back. Only
hepatitis C has a treatment that can cure it and these drugs are very
new and very expensive.
Peter White is a Professor in Microbiology and Molecular Biology at UNSW.