There are five hepatitis viruses (designated A, B, C, D & E) and they all share two things in common:
And that's where the similarities end. In the family tree of all the viruses that exist on the whole planet, these 5 viruses are barely even related to each other! In fact, hepatitis C virus is more closely related to Dengue Virus and Zika Virus then it is to hepatitis B virus! Hepatitis A virus is more closely related to poliovirus (the virus that causes polio) then it is to either hepatitis B or C viruses. Hepatitis D virus can only infect people who are already infected with hepatitis B virus (it piggybacks on to hepatitis B virus to infect the cells of humans). Hepatitis E virus is a distant relative of hepatitis A virus, but it is more closely related to the virus that causes Rubella then it is to hepatitis A virus. And things don't get any simpler after this...
There are vaccines available against hepatitis A and B, but none against hepatitis C virus. There is treatment for hepatitis C virus infection that is very effective at curing the infection, however there is no cure for hepatitis B virus infection. The current treatments for hepatitis B virus infection are similar to HIV antiretroviral drugs, in that they just 'lock up' the virus, they don't eradicate it from the infected persons system, meaning that, like for HIV infection, life long disease monitoring and therapy is neccessary. Without treatment, hepatitis B and C cause a chronic infection that leads to severe liver damage, ultimately causing liver failure and liver cancer. Viral hepatitis is now the seventh leading cause of death world wide, and hepatitis C virus alone kills more people annually than HIV/AIDS.
So, I guess the title above is probably a little misleading, because the hepatitides (plural of hepatitis) are really not that easy at all...
The first of the hepatitis viruses I will discuss in more detail is hepatitis C virus (HCV). HCV is of the family Flaviviridae, (this family also contains members West Nile Virus, Dengue Virus, Zika Virus & Yellow Fever virus) in the genus Hepacivirus. HCV is a bloodborne virus and it can be transmitted through unsafe medical procedures (e.g. using unsterilised equipment or unscreened blood products), unsafe tattooing or piercing (e.g. in prison or other places where needles or ink pots may be reused), sharing drug injecting equipment (e.g. using a needle or syringe after someone else has already used it, using the same spoon as someone else to mix up, etc) and it may also be transmitted sexually, but this is much less common, is not fully understood and is related to specific sexual practises or circumstances (e.g. sexual transmission is more likely between men who have sex with men, if another sexually transmitted infection (STI) is present, if recreational drugs have been taken or when sex may involve mucosal trauma). Depending on the exact population of people (i.e. the genetic make-up, gender & age of the group), for roughly 25% of people who become infected with HCV, they will naturally clear the infection on their own, within 6 months of being infected, without any treatment. However, for the other 75%, they develop a chronic infection that, withouth treatment, slowly causes damage to the liver ('fibrosis') which eventually causes liver failure and liver cancer.
The best estimates are that there are 130–150 million people infected with HCV around the world at the moment, which compared to only 36.7 million people infected with HIV, gives you an idea of how prevalent this disease is. The infection caused by HCV was known as "Non-A, Non-B hepatitis" up till 1989, when HCV was first discovered. HCV isn't commonly sexually transmitted, like HIV is, yet there are four times as many people infected with HCV then there are with HIV. The prevalence of HCV, along with the fact it was only discovered in 1989, raises a few questions. First, how did so many people become infected with HCV? For how long was HCV spreading, unknown, through populations of humans before it was discovered? And where did this virus first come from? I hope you are as intrigued by these questions as I am, because I will begin answering them in subsequent posts, so stay tuned for the next instalment!
This blog is written by Sofia Bartlett; scientist and curious human being. Her bio can be viewed here.
© Sofia Bartlett and Rogue Transmissions, 2017. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author is strictly prohibited.