The five new cases were then identified and sent to the laboratory, Congo's Government said.
Since that time, no deaths have been reported among those hospitalised or among health workers treating the ill, it said.
A team of experts will go to Bikoro tomorrow to implement measures to avoid further spread of the disease, said the ministry statement. The team will also investigate how the outbreak first started, it said.
This is the ninth Ebola outbreak in Congo since 1976, when the deadly disease was first identified.
The most recent outbreak was in May 2017 that killed four of the eight people infected in Congo's Bas-Uele province in the northeast. That outbreak was quickly contained and was declared over in July 2017.
None of these outbreaks was connected to the massive outbreak in Guinea, Liberia and Sierra Leone that began in 2014 and left more than 11,300 dead.
Ebola occasionally jumps to humans from animals, including bats and monkeys.
Without preventive measures, the virus can spread quickly between people and is fatal in up to 90 per cent of cases.
There is no specific treatment for Ebola, which is spread through the bodily fluids of people exhibiting symptoms.
A new experimental vaccine has been shown to be highly effective against the virus, though quantities are currently limited.
WHO said it is working closely with Congo's Government to rapidly scale up its operations and mobilise health partners as it did successfully in Congo last year.
"Our top priority is to get to Bikoro to work alongside the Government of the Democratic Republic of the Congo and partners to reduce the loss of life and suffering related to this new Ebola virus disease outbreak," said Dr Peter Salama, WHO Deputy Director-General, Emergency Preparedness and Response.
- AP
