A cheat sheet from Andrew Reynolds on the most common infectious disease in the world

Hepatitis B (HBV) is a virus that infects the liver, and it is the most common infectious disease in the world. In the United States, an estimated 850,000 to 2.2 million people living with HBV, and about 10% of people living with HIV are co-infected with HBV. In recent years there have been increases in HBV infections among people who inject drugs (PWID) and in mother-to-child transmission in the U.S., directly related to the opioid crisis. Screening, vaccination and prevention, and HBV treatment are essential tools for addressing this public health problem. 

Hepatitis B transmission

Hepatitis B is transmitted in much the same way as HIV: It’s spread when blood, semen, vaginal fluids, and other body fluids of a person get into a person who is not infected or not protected by immunity (through vaccination or cleared infection). It is also commonly transmitted from mother to child during birth. The following have been associated with risk of transmission:

  • vertical (mother to child) transmission
  • condomless sex with an infected partner
  • sharing syringes and other drug-injection equipment (cookers, cotton, water, etc.)
  • sharing household items such as razors or toothbrushes with an infected person
  • other blood-to-blood contact
  • occupational exposure from needlesticks or other risks of blood-to-blood contact.

Testing for hepatitis B

Most people who become infected with HBV don’t know it because it rarely leads to signs or symptoms in the acute or chronic stages of infection. Over time, as the liver is damaged, noticeable symptoms may arise, but screening (testing) for the virus is the only way to determine if you have HBV.

Who should get tested:

Persons from endemic regions of the world:

  • persons born in a country with HBV rates greater than 2%
  • U.S.-born individuals who did not receive a vaccination, and whose parents were born in a country with HBV rates greater than 8% 

Persons with certain medical conditions:

  • women who are pregnant 
  • babies born to mothers who are HBV-infected 
  • individuals on hemodialysis 
  • people needing immunosuppressive therapy (such as chemotherapy or those receiving organ transplants)
  • people with chronic HCV infection before undergoing DAA therapy
  • donors of blood, plasma, organs, tissues, or semen
  • anyone with an unexplained elevated ALT/AST 


  • people who inject drugs
  • men who have sex with men
  • people living with HIV 
  • household, needle-sharing (including injection equipment), or sex partners of people with chronic HBV 
  • people who are the sources of blood or body fluids resulting in a potential HBV exposure (such as an occupational needle stick or blood splash or sexual assault) where post-exposure prophylaxis may be necessary


Vaccination for hepatitis B

Hepatitis B is vaccine-preventable. It is safe and highly effective in preventing HBV, successful over 95% of the time. After the first dose, the vaccine is administered one month and six months later. Adults may be eligible for a two-dose sequence, in which the first dose is provided and the second one is given at least one month later (minimum of 28 days after the first one). The vaccine remains effective the rest of your life with no need for a booster shot ever. 

Who should be vaccinated against HBV:

  • all infants, beginning at birth
  • all children under the age of 19 years who have not been vaccinated previously
  • susceptible sex partners of hepatitis B surface antigen (HBsAg)-positive persons
  • sexually active persons who are not in a long-term, mutually monogamous relationship (e.g., more than one sex partner during the previous 6 months)
  • anyone seeking care for a sexually transmitted disease
  • men who have sex with men
  • injection drug users
  • susceptible household contacts of HBsAg-positive persons
  • health care and public safety workers at risk for blood exposure
  • anyone with end-stage renal disease
  • residents and staff of facilities for developmentally disabled persons
  • travelers to regions with intermediate or high rates of endemic HBV infection
  • anyone with chronic liver disease
  • anyone living with HIV
  • adults with diabetes ages 19–59 years (at the discretion of clinicians for diabetics aged 60 and older)
  • anyone seeking protection from HBV infection—acknowledgment of a risk factor is not required

If a person already has HBV, vaccination offers no protection against disease progression or risk of liver disease. Check for immunity or chronic infection before getting vaccinated. 

Most people will clear HBV naturally and achieve immunity. Treatment for HBV is called for in anyone with cirrhosis, regardless of ALT or HBV viral load. Similarly, anyone living with chronic HBV who is undergoing immunosuppressive therapy should be treated to prevent an HBV flare-up. There are other scenarios where a person should be treated.