Overview
Hepatitis B Virus (HBV) is a serious viral infection that mainly affects the liver. It is caused by a DNA virus belonging to the Hepadnaviridae family. HBV infection can be either acute (short-term) or chronic (long-term). Acute infections may clear on their own, but chronic infections may stay in the body for years and increase the risk of severe liver diseases like cirrhosis, liver failure, and hepatocellular carcinoma (liver cancer).
HBV spreads through infected blood, unprotected sexual contact, sharing needles, tattoo equipment, razors, or from an infected mother to her baby during childbirth. Because the virus directly targets liver cells, early diagnosis and regular monitoring are important for controlling complications.
How HBV Enters and Behaves in the Body
HBV is not produced naturally in the body. It enters from an external source (another infected person). Once inside, the virus specifically attacks hepatocytes (liver cells). Inside these cells, HBV uses the body’s cellular machinery to:
- Multiply
- Produce viral proteins
- Create new viral particles
These newly created viruses then spread to more liver cells, continuing the infection cycle.
Why Understanding HBV Is Important
Even though HBV has no useful function in the human body (it is a harmful pathogen), learning about HBV is medically important because it helps:
- Understand how the virus damages the liver.
- Diagnose acute and chronic hepatitis B infections.
- Monitor disease progression and risk of cirrhosis or liver cancer.
- Guide doctors in choosing the right treatment.
- Improve vaccination strategies and prevention programs.
- Identify people at high risk so early care can be provided.
Causes of Low or Negative HBV Levels
A low or negative HBV test result usually means:
- No active infection currently.
- Successful response to the hepatitis B vaccine.
- Recovery from a past HBV infection, where the body has created protective antibodies.
- Good immunity and no complications.
This state is considered normal and healthy.
Symptoms of Low or Negative HBV Levels
If HBV is absent in the body, there are no symptoms, because the virus is not causing any damage. A negative result simply means you are not infected.
Causes of High or Positive HBV Levels
HBV levels become high or positive due to:
1. Acute Hepatitis B Infection
This occurs soon after exposure to the virus. Symptoms appear within weeks to months.
2. Chronic Hepatitis B Infection
If the virus stays in the body for more than 6 months, it becomes chronic. This is more common in people infected at birth or early childhood.
3. Reactivation of Old HBV Infection
In people who had past infection, the virus may become active again during:
- Cancer treatment
- HIV infection
- Organ transplant
- Long-term steroid therapy
(because immunity becomes weak)
Symptoms When HBV Levels Are High
Symptoms may differ depending on whether the infection is acute or chronic.
Common Symptoms Include:
- Weakness and fatigue
- Loss of appetite
- Fever (sometimes)
- Nausea or vomiting
- Yellowing of skin and eyes (jaundice)
- Dark-colored urine
- Pale or clay-colored stools
- Pain on the right upper side of the abdomen (liver area)
Chronic HBV Symptoms
Many people with chronic HBV remain symptomless for years. But silent damage continues, increasing the risk of:
- Cirrhosis
- Liver failure
- Liver cancer
This is why regular monitoring is important even if symptoms are not present.
Reference Ranges and Interpretation
HBV is diagnosed by measuring several markers in the blood. No single test gives complete information. Doctors usually check a combination of these:
1. HBsAg (Hepatitis B Surface Antigen)
- Positive: Active HBV infection (acute or chronic)
- Negative: No infection
2. Anti-HBs (Hepatitis B Surface Antibody)
- Positive: Immunity due to past infection or vaccination
- Negative: Not immune
3. HBeAg (Hepatitis B e Antigen)
- Positive: High infectivity (virus is multiplying quickly)
4. Anti-HBe
- Positive: Lower infectivity
5. HBV DNA
- Measures viral load, that is, how much virus is in the blood.
Higher levels mean active virus replication.
6. Anti-HBc (Core Antibody)
Indicates past or current infection.
Interpretation is done by combining all the markers together.
Sample Type Used for HBV Testing
- Blood sample (serum or plasma) is typically used.
- A liver biopsy may be recommended if severe liver disease is suspected.
- Ultrasound, FibroScan, or CT scan may be used to assess liver condition.
Test Preparation
Most HBV tests do not require fasting. However:
- Avoid alcohol for 24–48 hours before the test.
- Inform your doctor about any antiviral medications.
- If pregnant, inform your healthcare provider, as HBV testing is part of routine pregnancy screening.
When to Consult a Doctor
Seek medical advice immediately if you notice:
- Yellowing of eyes or skin (jaundice)
- Pain in the upper right abdomen
- Severe fatigue or weakness
- Dark urine or very pale stools
- Unexplained weight loss
- Exposure to someone with hepatitis B
- Symptoms of liver failure (confusion, swelling of feet or abdomen)
- If you are pregnant and haven’t been tested for HBV
- If your HBV test shows positive markers
Early diagnosis can prevent severe long-term complications.
Important Word Explanations
- HBV: Hepatitis B Virus, a virus that infects the liver.
- Hepatocytes: Liver cells where the virus multiplies.
- Cirrhosis: Permanent scarring of the liver.
- Hepadnaviridae: The virus family to which HBV belongs.
- Antibodies: Protective proteins made by the body’s immune system.
- Jaundice: Yellowing of skin and eyes due to liver damage.
- Viral Load: The amount of virus present in the blood.
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