Dramatic warning of World Health Organization: Disaster threatens

"There is a high risk of the spread of the polio virus. It can also spill over internationally," the head of the WHO's health emergency team in Gaza, Ayadil Saparbekov, told reporters in Geneva via video link from Jerusalem.

He said the assessment, which he hopes will be completed by the end of the week, will allow health officials to issue recommendations, "including the need for mass vaccination."

Poliomyelitis is a highly contagious virus that can attack the nervous system and cause paralysis, and it mostly affects children under the age of five.

"I am extremely worried about the outbreak of an epidemic in Gaza. And this is not only poliomyelitis, but different epidemics of infectious diseases," said Saparbekov.

The Israeli military said that, with the cooperation of international groups, enough vaccines have been brought in to cover more than a million people in Gaza, which has a total population of about 2.3 million.