At least 3,700 children in Guinea, Liberia and Sierra Leone who have lost one or both parents to Ebola this year face being shunned, the UN has said.
Carers were urgently needed for these orphans, Unicef said.
A basic human reaction like comforting a sick child has been turned “into a potential death sentence”, it added.
The World Health Organization (WHO) says more than 3,000 people have died of Ebola in West Africa – the world’s most deadly outbreak of the virus.
The figure on the number of Ebola orphans follows a two-week assessment mission by the UN children’s agency to the three countries worst-affected by the outbreak. An earlier version of this story said that 4,900 children had lost parents but the correct figure is 3,700.
It found that children as young as three or four years old were being orphaned by the disease.
Children were discovered alone in the hospitals where their parents had died, or back in their communities where, if they were lucky, they were being fed by neighbours – but all other contact with them was being avoided.
“Thousands of children are living through the deaths of their mother, father or family members from Ebola,” Unicef’s Manuel Fontaine said in statement about his two-week visit to the region.
“These children urgently need special attention and support; yet many of them feel unwanted and even abandoned,” he said.
“Orphans are usually taken in by a member of the extended family, but in some communities, the fear surrounding Ebola is becoming stronger than family ties.”
The number of Ebola orphans has spiked in the past few weeks and preliminary reports suggest that it is likely to double by mid-October, Unicef said.
There was an urgent need to establish a system for identifying and caring for Ebola orphans, it said.
Unicef will be holding a meeting on the issue in Sierra Leone next month but before then it wants potential carers to come forward.
“Ebola is turning a basic human reaction like comforting a sick child into a potential death sentence,” Mr Fontaine said.
“We cannot respond to a crisis of this nature and this scale in the usual ways. We need more courage, more creativity, and far far more resources.”