Australian Antigen is a common name for Hepatitis B surface antigen (HBsAg). It is a protein that is present on the surface of the hepatitis B virus (HBV) and indicates a current or past infection with the virus.

This antigen was first discovered in 1965 by Baruch Blumberg, who later won the Nobel Prize in medicine in 1976 for his work on the discovery of HBsAg. As of now, HBsAg is a staple in HBV screening, diagnosis, and vaccination all over the world.

Causes of Hepatitis B Infection

Hepatitis B is caused by the hepatitis B virus (HBV), which is transmitted in blood, semen, and other bodily fluids from an infected person. The virus is highly contagious and can be transmitted through:.

Sexual contact with an infected person
Sharing of needles or other injection equipment
From mother to child during childbirth
Exposure to blood or open sores of an infected person

How HBsAg is used in diagnosis

HBsAg is detected in a blood sample through a test called a Hepatitis B surface antigen test. This test is commonly included in routine blood tests as well. The presence of HBsAg in the blood for more than six months indicates chronic hepatitis B.

This test can be used to diagnose an acute or chronic HBV infection, monitor the effectiveness of the treatment of an infection, and screen for HBV exposure in people who have an increased risk of infection such as health care workers, those with multiple sexual partners, and injection drug users.

Transmission of infection

HBV is spread through contact with blood or other bodily fluids like semen and vaginal fluids. Some modes of transmission are:.

Sex with an infected person: The virus can be transmitted through unprotected sex with an infected person.
Sharing needles or other equipment that contains blood: HBV is a resilient virus that can survive outside the human body and remain infectious for up to seven days. If needles, syringes, or other injection equipment contaminated with infected blood are shared, it can result in the spread of HBV.
Perinatal or vertical transmission: A mother infected with HBV can transmit the virus to her baby during childbirth. However, getting a vaccine within 12 hours of birth can prevent this mode of transmission.
Direct contact with infectious blood: Direct contact with infected blood can happen in many ways, including sharing razors or toothbrushes, or coming into contact with bodily fluids during sports, such as wrestling or boxing.

Prevention

There is no cure for HBV, but the good news is that it can be prevented by vaccination. The vaccine is commonly given in three doses over six months. It is important to complete the full course of vaccination to be protected against the virus.

Along with the vaccine, there are other prevention techniques like:.

Using condoms during sex to reduce the risk of transmission
Avoiding sharing of razors, toothbrushes, and personal items that can cause exposure to infected blood
Avoiding injectable drug use, and if this is not possible, using sterile needles and equipment

Risks and Complications

HBV can lead to serious health complications. Chronic infection can increase the risk of cirrhosis, liver cancer, liver failure, and ultimately death.

The risk of developing chronic HBV infection is higher in people who get infected as infants or young children. The risk is lower in adults. Hence, there is a high risk of complications among children with HBV infection who live in areas where HBV is highly endemic.

Testing and Diagnosis Guidelines

The Centers for Disease Control and Prevention (CDC) advise testing for HBV in people who:.

Have been sexually active with multiple partners or have a history of sexually transmitted infections
Have injected drugs in the past or are currently inject drugs
Have been in close contact with someone who has chronic HBV infection
Are men who have sex with men
Are pregnant women
Have chronic liver disease
Are on long-term hemodialysis
Are being treated with chemotherapy for cancer

Treatment

Treatment for HBV depends on whether the infection is acute or chronic. Acute hepatitis B infections usually resolve on their own, and treatment focuses on supportive care like rest and hydration.

However, if the infection becomes chronic, antiviral medicines like tenofovir disoproxil fumarate and entecavir can help. These drugs slow down the virus’ ability to replicate in the liver and reduce the risk of cirrhosis. Some people may require a liver transplant when the liver is severely damaged.

Conclusion

HBsAg or the Australian Antigen is a protein found on the surface of the hepatitis B virus that indicates a current or past infection with the virus.

The antigen is commonly detected in a blood sample through a test called a Hepatitis B surface antigen test. While there is no cure for HBV, it can be prevented by vaccination. Vaccination coupled with measures like using condoms, avoiding shared needles, and avoiding injectable drug use are effective preventive techniques that can halt the spread of HBV.

Timely testing, diagnosis, and treatment of HBV can reduce the risk of complications that can arise from the infection.