Hundreds of people in southeastern Chad are at risk of dying from a worsening hepatitis E outbreak which has killed 11 people since September, medical charity Medecins Sans Frontieres (MSF) said on Thursday.

Some 885 people in the Salamat region have been treated for symptoms of jaundice, which can indicate hepatitis E, MSF said.

Most, if not all of the patients, are likely to be suffering from hepatitis E, a liver disease which spreads through water contaminated with faeces, the aid group said. It has recorded 70 cases and 11 deaths, including four pregnant women, to date.

However, the death toll from the outbreak could be higher due to cases which may not have been treated in health facilities, according to the World Health Organization (WHO).

More than 600 MSF staff are working alongside Chad's health ministry to test for new cases, treat patients and improve water supplies and sanitation in the regional capital of Am Timan.

The aid group said it had also rolled out a large scale chlorination campaign at the 72 water points in Am Timan, and is holding education sessions to explain the importance of handwashing with soap and chlorinated water.

In a statement, MSF's head of mission in Chad, Rolland Kaya, called for more aid agencies to step in to improve water sanitation in the region amid mounting cases of the disease.

"As a medical organisation, it is not usually MSF's job to intervene on a large scale in water chlorination activities, but with no other options to help stop the spread of the virus, we are obliged to fill this gap," Kaya added.

Hepatitis E affects an estimated 20 million people around the world each year, with typical symptoms including jaundice, dark urine and pale stools, abdominal pain and tenderness, nausea and vomiting, fever, and an enlarged, tender liver.

For most people, the infection runs its course with a few long-term complications, but the mortality rate for pregnant women is about 25 percent. An effective vaccine for the virus is currently only licensed for use in China.