Looming health disaster for displaced Palestinians living in tent camps, where sewage flows freely, contaminating water.

Poliovirus has been detected in samples of sewage water in the densely populated Gaza Strip, placing “thousands” of Palestinians at risk of contracting the highly infectious disease that can cause paralysis.

Gaza’s Ministry of Health said it had detected “component poliovirus type 2” in coordination with UNICEF, the United Nations children’s agency.

“Detecting the virus that causes polio in wastewater heralds a real health disaster and exposes thousands of residents to the risk of contracting polio,” it said on Thursday in a statement.

The virus could be found in sewage “that collects and flows between the tents of the displaced”, said the ministry. Already scarce supplies of drinking water in the densely populated Strip are at risk of being contaminated by the virus.

Authorities in the central Gaza city of Deir el-Balah this week predicted that “roads will be flooded by wastewater” and “diseases will spread” after it turned off sewage water pumping and treatment stations.

“We’re talking about a very grim medical reality,” said Al Jazeera’s Tareq Abu Azzoum, reporting from Deir el-Balah, where 700,000 people have arrived in search of safety from fighting and air strikes.

The Israeli military’s escalation of attacks on “water wells, sanitation and water waste treatment”, and its obstruction of “essential hygiene supplies” into the Strip had created a “suitable environment for the spread of different diseases,” he said.

Dr Tanya Haj-Hassan, a paediatric intensive care physician, told Al Jazeera the presence of the virus in sewage was a “ticking time bomb”.

“Normally if you have a case of polio, you’re going to isolate them, you’re going to make sure that they use a bathroom that nobody else uses, make sure that they’re not in close proximity to other people, [but] that’s impossible,” she said.

“You have everybody clustering in refugee camps at the moment without vaccines for at least the past nine months, including children who would otherwise have been vaccinated for polio and adults who, in the setting of an outbreak, should receive a booster, including healthcare workers,” she added.

The spread of the disease among healthcare workers would be “catastrophic”, Haj-Hassan said, for a healthcare system already “annihilated by direct targeting, by abductions of healthcare workers, by [the] killing of healthcare workers”.

Earlier, the Israeli Ministry of Health said it had evidence of the “component poliovirus type 2”, found in sewage samples taken inside the Gaza Strip.

It instructed the Israeli army to vaccinate all troops in the Gaza Strip as well as those who are about to enter, and recommended a booster for those already vaccinated.

The discovery of poliovirus came after a European activist group released a report saying the Gaza Strip is “drowning” in hundreds of thousands of tonnes of human waste and rubble from the war.

UN health agencies started a global campaign in 1980 to eradicate polio, most often spread through sewage and contaminated water, but there has been a resurgence in recent years in Afghanistan and Pakistan.