Hepatitis B

• Abdominal pain
• Dark urine
• Joint pain
• Loss of appetite
• Nausea and vomiting
• Weakness and fatigue
• Yellowing of your skin and the whites of your eyes (jaundice)

Most infants and children with hepatitis B never develop signs and symptoms. The same is true for some adults.

Causes

Hepatitis B infection is caused by the hepatitis B virus (HBV). HBV is passed from person to person through blood, semen or other body fluids. When HBV enters your liver, it invades the liver cells and begins to multiply. This causes inflammation in the liver and leads to the signs and symptoms of hepatitis B infection.

Common ways HBV is transmitted include:

• Sexual contact. You may become infected if you have unprotected sexual contact with an infected partner whose blood, saliva, semen or vaginal secretions enter your body.
• Sharing needles. HBV is easily transmitted through needles and syringes contaminated with infected blood. Sharing intravenous (IV) drug paraphernalia puts you at high risk of hepatitis B.
• Accidental needle sticks. Hepatitis B is a concern for health care workers and anyone else who comes in contact with human blood.
• From mother to child. Pregnant women infected with HBV can pass the virus to their babies during childbirth.

Acute vs. chronic hepatitis B

Hepatitis B infection may be either short-lived (acute hepatitis B) or long lasting (chronic hepatitis B).

• Acute hepatitis B infection lasts less than six months. If the disease is acute, your immune system is usually able to clear the virus from your body, and you should recover completely within a few months. Most people who acquire hepatitis B as adults have an acute infection.
• Chronic hepatitis B infection lasts six months or longer. When your immune system can't fight off the virus, hepatitis B infection may become lifelong, possibly leading to serious illnesses such as cirrhosis and liver cancer. Most infants infected with HBV at birth and many children infected between 1 and 5 years of age become chronically infected. Chronic infection may go undetected for decades until a person becomes seriously ill from liver disease.

Risk factors

Your risk of hepatitis B infection is increased if you:

• Have unprotected sex with more than one partner
• Have unprotected sex with someone who's infected with HBV
• Have a sexually transmitted disease such as gonorrhea or chlamydia
• Are a man who has sexual contact with other men
• Share needles during intravenous (IV) drug use
• Share a household with someone who has a chronic HBV infection
• Have a job that exposes you to human blood
• Receive hemodialysis for end-stage kidney (renal) disease
• Travel to regions with high infection rates of HBV, such as Africa, Central and Southeast Asia, and Eastern Europe

Complications

Having a chronic HBV infection can lead to serious complications, such as:

• Scarring of the liver (cirrhosis). Hepatitis B infection may cause inflammation that leads to extensive scarring of the liver (cirrhosis). Scarring in the liver may impair the liver's ability to function.
• Liver cancer. People with chronic hepatitis B infection have an increased risk of liver cancer.
• Liver failure. Acute liver failure is a condition in which all the vital functions of the liver shut down. When that occurs, a liver transplant is necessary to sustain life.
• Hepatitis D infection. Anyone chronically infected with HBV is also susceptible to infection with another strain of viral hepatitis — hepatitis D. You can't become infected with hepatitis D unless you're already infected with HBV. Having both hepatitis B and hepatitis D makes it more likely you'll develop complications of hepatitis.
• Kidney problems. Hepatitis B infection can cause kidney problems that may lead eventually to kidney failure. Children are more likely to recover from these kidney problems than are adults, who may experience kidney failure.
• Blood vessel inflammation (vasculitis). Inflammation in the blood vessels can cause further complications, though this is a rare complication of hepatitis B infection.

Diagnosis

Screening healthy people for hepatitis B

Doctors sometimes test certain healthy people for hepatitis B infection. This is recommended because hepatitis B infection often begins damaging the liver before it causes signs and symptoms. Testing for hepatitis B infection in people who have a high risk of coming in contact with the virus may help doctors begin treatment or recommend lifestyle changes that may slow liver damage.

People who may want to talk to their doctors about screening for hepatitis B infection include:

• Anyone who lives with a person who has hepatitis B infection
• Anyone who has had sex with a person who has hepatitis B infection
• Anyone with an unexplained, abnormal liver enzyme test
• Babies born to women with hepatitis B
• HIV-positive people
• Immigrants, including internationally adopted children, from areas of the world where hepatitis B is more common, including Asia, the Pacific Islands, Africa and Eastern Europe
• Injection drug users
• Inmates
• Men who have sex with men
• People who have one or more parents from an area of the world where hepatitis B is more common
• People who receive kidney dialysis
• Pregnant women

Blood tests to detect hepatitis B infection

Blood tests used to diagnose hepatitis B infection include:

• A test to determine whether you can easily pass HBV to others. The hepatitis B surface antigen (HBsAg) test looks for hepatitis B surface antigen — part of the outer surface of the virus. Testing positive for this antigen means you have an active hepatitis B infection and can easily pass the virus to others. A negative test means you're probably not currently infected.
• A test to determine whether you're immune to HBV. The antibody to hepatitis B surface antigen (anti-HBs) test determines if you have antibodies to HBV. Having antibodies can be due to a prior HBV infection from which you've recovered. Or, it can mean you may already have been vaccinated. In either case, a positive anti-HBs test means you can't infect others or become infected yourself because you're protected by the vaccine or your own natural immunity.
• A test to determine whether you have had or currently have a hepatitis B infection. Although the antibody to hepatitis B core antigen (anti-HBc) test identifies people who have a chronic infection, the results can sometimes be ambiguous. If you test positive for hepatitis B core antibodies, you may have a chronic infection that you can transmit to others. But you may also be recovering from an acute infection or have a slight immunity to HBV that can't otherwise be detected. How this test is interpreted often depends on the results of the other two tests. When the results are uncertain, you may need to repeat all three tests.

Additional tests to gauge liver health and infection severity

If you receive a diagnosis of hepatitis B, your doctor may perform tests to check the severity of the HBV infection as well as the health of your liver. These tests include:

• A test to determine how likely you are to spread HBV to others. The E antigen blood test looks for the presence of a protein secreted by HBV-infected cells. A positive result means you have high levels of the virus in your blood and can easily infect others. If the test is negative, you have lower blood levels of HBV and are less likely to spread the infection.
• A test to determine how much HBV DNA is in your blood. The hepatitis B DNA test detects parts of HBV DNA in your blood, indicating how much virus is present (viral load). Assessing your viral load can help monitor how well antiviral therapy is working.
• Tests to measure liver function. Liver function tests may gauge the amount of damage that has occurred in your liver cells.

Removing a sample of liver tissue for testing

During a liver biopsy, your doctor inserts a thin needle through your skin and into your liver. A small sample of liver tissue is removed for laboratory analysis. A biopsy may show the extent of any liver damage and may help determine the best treatment for you. 

References:

http://www.who.int/features/qa/76/en/

https://en.wikipedia.org/wiki/Hepatitis

http://www.medicalnewstoday.com/articles/145869.php

http://www.healthline.com/health/hepatitis

https://www.nlm.nih.gov/medlineplus/hepatitis.html

http://www.cdc.gov/hepatitis/

http://www.cdc.gov/hepatitis/hcv/cfaq.htm