Hepatitis B Virus and Hepatitis C Virus are deemed the most dangerous of the known Hepatitis viruses. The World Health Organisation (WHO) estimates that more than 240 million people have chronic (long-term) Hepatitis B Virus infections and more than 780,000 people die every year due to the acute or chronic consequences of Hepatitis B. The WHO also estimates that 130–150 million people globally have a chronic Hepatitis C Virus infection and up to 500,000 people die each year from Hepatitis C-related liver diseases.
A vaccine is available for Hepatitis B and the farmaceutical industry is hard at work to create a vaccine for Hepatitis C.
Pregnant women are particulary at risk of more severe disease, especially if infected in the third trimester of pregnancy.
The faecal–oral route is a well-established mode of transmission for Hepatitis A Virus and outbreaks are therefore manifestations of the poor sanitation practices and lack of clean water supplies often found in developing countries. Still, doctors do not consider Hepatitis A to be a serious illness, even though liver failure and death can occur sporadically from an infection.
A vaccine is available. Get it, even if you're not planning to travel to a region where the disease is endemic.
 WHO: Fact sheet Hepatitis B. See here.
 WHO: Fact sheet Hepatitis C. See here.
 Lozano et al: Global and regional mortality from 235 causes of death for 20 age groups in 1990 and 2010: a systematic analysis for the Global Burden of Disease Study 2010 in Lancet – 2012
 Cho et al: Hepatitis A virus infection during pregnancy in Korea: Hepatitis A infection on pregnant women in Obstetrics and Gynecology Science - 2013