The UN air coordinator expressed shock that vehicles of the workers were attacked.
The UNHCR put the numbers fleeing the fighting at 450,000 and said at least 200,000 of the internally displaced people had been cut off from humanitarian aid.
He said the militants kidnapped several others, who are now missing.
M23 has seized many areas of North Kivu province in eastern DRC since last October.
The Allied Democratic Forces (ADF), a Ugandan armed group based in eastern Congo with ties to Islamic State, has been blamed for the killings.
According to the UN, nearly 25 million Nigerians are at risk of hunger between June and August this year if urgent action is not taken.
UNICEF says the lives of thousands of children in overcrowded, unsanitary camps for IDPs in eastern Democratic Republic of the Congo are seriously at risk.
WHO disclosed that all five patients had died, and 234 contacts were identified and under surveillance, while 1,013 people, including frontline workers, were vaccinated.
Civil society leaders estimated that between 30 and 50 people were killed during the attack.
Guinea’s health department had reported that four people died of Ebola in a resurgence of the disease that first emerged five years ago.
