A fourth person has likely died from Ebola in remote northeastern Democratic Republic of Congo during the most recent outbreak, the World Health Organization (WHO) said on Sunday.

The overall number of cases is now at 37 from 29.

WHO's Congo spokesman, Eugene Kabambi, told Reuters that of the 37 cases of hemorrhagic fever discovered since early May:

Two have been confirmed as Ebola.

Three, including the latest death, are considered probable.

Thirty-two are suspected.

The WHO confirmed the Ebola outbreak earlier this month, the first in the Democratic Republic of Congo since 2014.

Health authorities are monitoring 416 people who came into contact with sufferers and have dispatched mobile laboratories to the zone to more quickly test people who display symptoms, Kabambi said.

The affected zone's extreme isolation has helped contain the highly contagious spread of the virus, though a lack of telecommunications, few paved roads and a shortage of thermometers have hindered the response.