The World Health Organization (WHO) is extremely worried over the prospect of a poliovirus outbreak in the Gaza Strip after it was detected in the sewage.

Ayadil Saparbekov, the World Health Organization's head of health emergencies in the occupied Palestinian territories, said to reporters in Geneva via video-link from Jerusalem: “I am very much worried.”

Saparbekov noted that the organization has not yet collected human samples, and it remains unclear if there is anyone infected with the virus – according to Agence France-Presse (AFP).

"I'm extremely worried about outbreaks happening in Gaza," he said, pointing to the confirmation late last year that hepatitis A was spreading, "and now we may have polio".

"With the crippled health system, lack of water and sanitation, as well as lack of access of the population to health services... this is going to be a very bad situation," he warned.

"We may have more people dying of different communicable diseases than from the injury-related diseases."

UN agencies said vaccine-derived type-2 poliovirus in six environmental samples collected from the sewage by the Global Polio Laboratory Network in the Gaza Strip on June 23.

This is likely attributed to a type of vaccine against polio which contains small amounts of weakened but live polio which can occasionally cause outbreaks.

Oral polio vaccine (OPV) replicates in the gut and can be passed to others through fecal-contaminated water -- meaning it won't hurt the child who has been vaccinated, but could infect their neighbors in places where hygiene and immunization levels are low.