Hepatitis Info from the NIH for you -there is not a % given but I think you can see how widespread it is.
Quote: Causes, incidence, and risk factors
The disease can be caused by:
Infections from parasites, bacteria, or viruses (such as Hepatitis A, B, or C) Liver damage from alcohol, drugs, or poisonous mushrooms An overdose of acetaminophen, which is rare but deadly Immune cells in the body attacking the liver and causing autoimmune hepatitis Other medications that can cause damage to the liver include methyldopa (used uncommonly for high blood pressure), isoniazide for tuberculosis, seizure medications (like valproate and phenytoin), chlorpromazine, amiodarone (for irregular heart rhythm), and certain antibiotics (including trimethoprim-sulfamethoxazole and erythromycin). If you need to take any of these, your doctor will follow your liver function closely.
Liver disease can also be caused by inherited disorders such as cystic fibrosis and Wilson's disease, a condition that involves having too much copper in your body; the excess copper deposits in organs like your liver.
Hepatitis may start and resolve quickly (acute hepatitis), or cause long-term disease (chronic hepatitis). In some instances, progressive liver damage, liver failure, or even liver cancer may result.
The severity of hepatitis depends on many factors, including the cause of the liver damage and any underlying illnesses you have. Hepatitis A, for example, is generally short-lived, not leading to chronic liver problems.
Common risk factors include:
Intravenous drug use Acetominophen overdose -- the dose needed to cause damage is close to the effective dose, so be careful to take it only as directed; DO NOT use if you already have underlying liver damage Risky sexual behaviors (like having multiple sexual partners and unprotected intercourse) Eating contaminated foods Travel to an endemic area, like Asia, Africa, or South or Central America Living in a nursing home or rehabilitation center Family member who recently had hepatitis A Alcohol use Organ transplant recipient AIDS Blood transfusion received prior to 1990 (before hepatitis C blood test was available) Newborns of mothers with hepatitis B or C (can be transmitted during delivery) Healthcare workers, including dentists and dental hygienists, because of blood contact Receiving a tatoo