An earlier outbreak, involving eight deaths among 12 cases, was reported from Boloko village in the Bolomba health zone on 21 January, the WHO said.
As of 16 February there have been 431 cases and 53 deaths in two outbreaks across remote villages in Équateur province, the World Health Organization (WHO) said in a bulletin.
Samples from 13 cases have tested negative for Ebola and Marburg, but the WHO said health teams were locally investigating other potential causes, including malaria, food poisoning, typhoid, meningitis or other viral haemorrhagic fevers.
An unknown illness first discovered in three children who ate a bat has killed more than 50 people in the Democratic Republic of the Congo (DRC) over the past five weeks, according to health workers.
The larger outbreak, reported on 13 February from Bomate village in the Basankusu health zone, has killed 45 people out of 419 cases.
