BBC What's hepatitis B?

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http://www.bbc.co.uk/health/phys ... s/hepatitisb1.shtml

Inflammation of the liver - hepatitis - has many causes, including several viruses. One of the most common but least known about is hepatitis B, which is 100 times more infectious than HIV.

What is hepatitis B?

Hepatitis B is a viral infection of the liver, which follows a very variable course. The hepatitis B virus (HBV) can cause an acute illness that resolves itself quickly without causing long-term liver damage. However, in about 20% of cases it causes a chronic illness that lasts more than six months, sometimes for life, with symptoms that come and go. In 15-40% of those with chronic infection cirrhosis, liver cancer or liver failure develop, and so the infection may eventually be fatal.

Hepatitis B is not very common in the UK, with new infections occurring in about 7 out of every 100,000 of the population every year, usually in adults. But worldwide it is a major health problem. In Asia and most of Africa most people pick up the infection around the time of birth or during childhood. As a result two billion people worldwide are infected with hepatitis B, with 350 million suffering from chronic HBV infection. It is the 10th leading cause of death worldwide.

The virus is usually transmitted through contact with infected blood or body fluids. Only a tiny amount of blood is needed to transmit the virus because it's so infectious. The hepatitis B virus may also be present in saliva, vaginal secretions, breast milk and other bodily fluids.

In the UK infection commonly occurs through unprotected sexual intercourse, the sharing of contaminated needles by drugs users, accidental injury with a contaminated needle (if needles used for tattooing, body piercing or acupuncture are contaminated) and sharing razors.

In countries where screening of blood products isn't routine, or where medical equipment isn't adequately sterilised, hepatitis B may be transmitted during medical treatment.

Many people contract hepatitis B while on holiday, especially in countries where it is very prevalent, when unprotected sex, experimenting with drugs and accidents needing medical treatment are far more likely.

Symptoms

The incubation period of the hepatitis B virus before symptoms develop is between six weeks and six months. In the acute phase symptoms vary. Roughly one-third of cases have no symptoms - this is called a silent or subclinical infection, or sometimes anicteric infection, meaning there is no jaundice or yellow appearance of the skin and membranes. In another third of cases, the infection causes mild symptoms similar to those of a flu-like illness, with weakness, aches, headache, fever, loss of appetite, diarrhoea, jaundice, nausea and vomiting.

In the final third of cases, the acute phase of infection can cause severe illness that last many months. In addition to the flu-like symptoms, there's abdominal pain, diarrhoea and jaundice.

Jaundice occurs in hepatitis infections because the liver becomes unable to remove a substance called bilirubin from the blood. This is a pigment that builds up in the body, causing the skin and whites of the eyes to turn yellow.

Rarely, rapid liver failure develops, which may need a life-saving liver transplant.

In as many as one in five cases, the infection then goes into a chronic phase, where people may be apparently healthy with no symptoms but carrying and shedding the virus (known as healthy carriers). Alternatively, they may develop a chronic active hepatitis, with similar symptoms to the acute phase of the infection and also fatigue, poor appetite, nausea and abdominal discomfort.

Causes and risk factors

In the UK the people most at risk of contracting hepatitis B are injecting drug users, people who have unprotected sex with different partners, close family members of someone with the infection, babies born to infected mothers and travellers to high-risk countries who come into contact with infected blood and other bodily fluids.

Hepatitis B is considered an occupational hazard for healthcare workers, the police and the emergency services.

Practising safe sex by using condoms and not sharing needles when using drugs can reduce the risk of infection. The same advice applies when travelling.

When having any body piercing, tattoo or acupuncture, make sure the business is registered with the local authority, that the needles used are disposable and that an autoclave is used for any equipment that's sterilised. If the proprietor cannot confirm these, go elsewhere.

Normal social contact carries no risk of infection. You can't catch hepatitis B from toilet seats or by touching an infected person. Clothing with the virus is thought to be killed by a normal hot wash in a washing machine, and by washing-up liquid and hot water for plates and cutlery.

There's an effective vaccination to protect people from hepatitis B infection. It's available from your GP or high street travel centres, who will advise you whether you need it.

Family and other household members of an infected person should be vaccinated against hepatitis B. Healthcare workers, the police, the emergency services and anyone who is likely to come in contact with infected blood through their job should also be vaccinated.

Treatment and recovery

The majority of people with hepatitis B don't need specific treatment other than rest and they eventually make a full recovery. However it is important that the infection is monitored to check whether chronic disease develops, and the person is given advice about the risk of passing the infection on.

If the infection lasts more than six months (chronic hepatitis infection, where the virus continues to actively reproduce in the body) you may need more specific drug treatment to reduce the risk of permanent liver damage (cirrhosis) and liver cancer. Your GP should refer you to a specialist in either liver disease (a hepatologist) or general digestive diseases (a gastroenterologist). They may recommend treatment either with treatment called interferon, or with antiviral drugs.

Interferon (either alpha interferon or longer lasting pegylated interferon) is given as regular injections and helps boost the immune system to fight the infection. The response to interferon is variable, and some people who initially get better get worse again when the treatment is stopped. Others find that the side-effects of interferon mean that they cannot continue with treatment.

Several different antiviral drugs, known as nucleoside analogues, are also now used to treat chronic hepatitis. They are not a cure, but they suppress the virus. These drugs may also have side-effects - although not usually so severe as with interferon - and the virus may become resistant to them.

Occasionally, when there is severe damage to the liver, a liver transplant is recommended.
Advice and supportBritish Liver Trust
Helpline: 0800 652 7330
Email: [email protected]
Website: www.britishlivertrust.org.uk

This article was last medically reviewed by Dr Trisha Macnair in February 2009.

走遍四方

the ABC's of Hepatitis

Hepatitis Facts: Worldwide Snapshot
Basics: Hepatitis A (HAV)
Basics: Hepatitis B (HBV)
Basics: Hepatitis C (HCV)

Hepatitis Facts: Worldwide Snapshot

Hepatitis A Virus (HAV) Infection:
In 2005, there were an estimated 42,000 Hepatitis A infections.
Hepatitis A is the cause of 30 days of missed work and approximately $2,600 in lost wages each year.
Medical care alone for hepatitis A can cost $2,800 for each hospitalized case.
Approximately 100 Americans die each year from Hepatitis A.
The annual cost associated with Hepatitis A is estimated at $200 million in the U.S.
Hepatitis B Virus (HBV) Infection:
HBV is 100 times more infectious than HIV, the virus that can cause AIDS.
Hepatitis B vaccine can provide immunity in over 95% of young healthy adults.
An estimated 350 million people are infected globally with HBV.
Approximately 1 million die each year from complications from HBV.
70% of new cases occur among people between the ages of 15-39.
Every year 5,000 Americans die from cirrhosis and 1,000 from liver cancer due to HBV infections.
22,000 pregnant women in the U.S. are infected with HBV and can transmit it to their newborns.
HBV can live on a dry surface for at least 7 days.
Hepatitis C Virus (HCV) Infection:
3% of the world's population is infected with HCV, or approximately 170 million people. 90% of HCV patients who are in need of treatment today cannot afford it.
80% of affected people can become chronically infected and risk serious long-term clinical disease including cirrhosis and liver cancer.
8 countries – Bolivia, Burundi, Cameroon, Egypt, Guinea, Mongolia, Rwanda, and Tanzania – have an HCV prevalence above 10%.
7 countries/areas – Gabon, Libya, Papua New Guinea, Suriname, Vietnam, Zaire, and the United Nations Relief and Works Agency for Palestine Refugees in the Near East – have an HCV prevalence between 5 and 10%.
In developing countries, the primary sources of HCV infection include transfusion of blood or blood products from unscreened donors; transfusion of blood products that have not undergone viral inactivation; parenteral exposure to blood through the use of contaminated or adequately sterilized instruments and needles used in medical and dental procedures; the use of unsterilized objects for rituals (e.g. circumcision, scarification), traditional medicine (e.g. blood-letting) or other activities that break the skin (e.g. tattooing, ear or body-piercing); and intravenous drug use. Household or sexual contacts of HCV-infected persons are marginally at risk.
In developed countries, persons at risk of HCV infection include recipients of previously unscreened blood, blood products, and organs; intravenous drug users; individuals undergoing chronic hemodialysis; health care workers with percutaneous exposure from contaminated needles or sharps; persons who participate in high-risk sexual practices; and persons undergoing medical or dental procedures with inadequately sterilized instruments. Sexual and household transmission are uncommon.