Hepatitis D

Hepatitis D is a very small virus that can cause serious illness in the liver.

It belongs to a group of five known hepatitis viruses. These are named A, B, C, D, and E. Hepatitis D is unique because it is a satellite. This means it cannot grow or spread on its own. It must have the hepatitis B virus present to work. If someone gets both at once, it is called a coinfection. If they already have hepatitis B, it is called a superinfection. Superinfection is often the most serious type of infection. It can lead to liver failure or liver cancer.

How does this tiny virus work inside a person? The virus finds its way into liver cells through a specific path. It uses a transporter called NTCP to enter the cell. Once inside, the virus uses the cell's own tools to make copies. The virus does not have its own way to copy its genetic material. Instead, it uses the host cell's RNA polymerases to do the job. These are special tools the cell uses to read instructions. The virus makes different forms of RNA to build itself. It also uses a special part called a ribozyme to cut the RNA into the right shapes. This helps the virus turn into a complete, circular piece of genetic code.

Scientists have studied how this virus builds itself for many years. The virus makes a protein called HDAg. This protein comes in two different forms. The first form is a large protein called HDAg-L. The second form is a smaller protein called HDAg-S. A cellular enzyme called ADAR helps change the instructions to make both types. The small protein helps the virus copy itself in the early stages. The large protein helps build new virus particles in the later stages. Researchers like Georges Abou Jaoudé and Camille Sureau studied these parts. In 2005, they published work about how the virus enters cells.

There are many important facts to know about this virus. It is the smallest virus known to infect animals. Its genome is made of about 1700 nucleotides. The virus particle is a tiny sphere with a 36 nm diameter. Experts estimate that about 48 million people are infected with this virus. It is more common in places like the Mediterranean and sub-Saharan Africa. The fatality rate for this infection can be as high as 20%. This is the highest death rate of all the hepatitis infections.

Learning about hepatitis D helps us understand how to stay healthy. We can prevent this virus by using the hepatitis B vaccine. Because the D virus needs the B virus, the vaccine protects against both. Doctors recommend giving this shot to babies very soon after they are born. We can also stay safe by using clean needles for tattoos or piercings. Using protection like condoms also helps stop the spread. If someone is sick, doctors can use medicines like bulevirtide to help. This medicine blocks the virus from entering the liver cells.