"We are very much worried, because if there is one case of polio with a kid that is paralysed, it is already an outbreak".

This is according to World Health Organization spokesman, Tarim Jasarevic.

He was speaking about the polio outbreak in war-ravaged Syria that has paralysed at least 17 children since March, 2017.

Jasarevic pointed out that for every polio-caused paralysis, there are on average nearly 200 children who have the virus but no symptoms.

"The virus is circulating. It is very serious."

15 more cases have been confirmed since the WHO first announced, less than two weeks ago, that Syria had been hit by its first outbreak of the crippling disease since 2014.

The new cases all surfaced between March 3 and May 23, but were only just confirmed, since it can take up to two months to determine with certainty that a case of acute flaccid paralysis stems from polio, he said.

"It is expected that we will have more confirmations," Jasarevic warned.