Hepatitis
A syringe with a vaccine against hepatitis BGetty

Viral hepatitis infection affects 400 million people worldwide more than 10 times the number of people affected by HIV. Yet at present, just one in 20 people with viral hepatitis know they are infected, and only one in 100 with the disease is being treated.

Hepatitis is a term used to describe the inflammation of the liver as a result of viral infection or exposure to harmful or toxic substances such as drugs or alcohol. While some types of hepatitis will pass without causing permanent damage to the liver, chronic cases can cause cirrhosis, liver failure or cancer.

In 2013, an estimated 1.45 million people died of the disease – up from less than 500,000 in 1990.

"The world has ignored hepatitis at its peril," said Dr Margaret Chan, WHO director general. "It is time to mobilise a global response to hepatitis on the scale similar to that generated to fight other communicable diseases like HIV/AIDS and tuberculosis."

With better understanding of prevention, thousands of lives could be saved every year. There is a vaccine and treatment for hepatitis B, and although there is no vaccine for hepatitis C, antiviral medication has made is possible to cure 90% of patients within two to three months.

What are five main hepatitis viruses?

There are five unique hepatitis viruses – A, B, C, D and E.

Hepatitis A, or HAV, is most commonly transmitted through consumption of contaminated water or food. While the majority of infections in cases are mild and the patient is able to make a full recovery, some can be life-threatening in areas with poor sanitation. It can also be spread through sex or via injecting drugs.

The hepatitis B virus, HBV, is transmitted through exposure to infected blood, semen and other body fluids. In some rare cases, it can be transmitted from infected mothers to infants during birth. Hepatitis B can also be spread through contaminated blood transfusions and medical procedures and by injection drug use.

The most common type of hepatitis, hepatitis C, or HCV, is most commonly transmitted through exposure to infected blood by injection drug use. Transmission by unprotected sex is also possible, although less common. There is currently no vaccine for hepatitis C, although research into development is ongoing.

Hepatitis D (HDV) infections occur only in those who are infected with hepatitis B. Chronic hepatitis D can increase the risk of developing cirrhosis, scarring of the liver caused by continuous, long-term liver damage.

The hepatitis E virus is mostly transmitted through consumption of contaminated water or food and it is common in developing countries. It is largely spread by drinking water contaminated with the faeces of someone infected with hepatitis E. It is mostly prevalent in east and south Asia. Although the infection normally clears within 2 to 6 weeks, it can occasionally lead to acute liver failure.