An 18-month-old girl has died in a Belfast hospital after developing complications from chickenpox.
The Eastern Health Board said the baby had suffered from a rare infection after being ill with the virus.
The board said there had been six or seven cases of chickenpox in the girl's nursery, but this was not particularly unusual at this time of year.
Dr Philip Donaghy from the board said the risk to others was low and that people should not be unduly concerned.
"Our understanding - we have taken advice from England, experts in London, is that it is a very rare occurrence," he said.
"If I cast my own mind back, I can't think of any episode like this.
"It is an exceedingly rare situation so the risk to any other child is extremely small, almost negligible.
"So we would have to reassure parents that the risk to their children was extremely rare."