CAIRO >> The threat of polio is rising fast in the Gaza Strip, prompting aid groups to call for an urgent pause in the war so they can ramp up vaccinations and head off a full-blown outbreak. One case has been confirmed, others are suspected and the virus was detected in wastewater in six different locations in July.

Polio was eradicated in Gaza 25 years ago, but vaccinations plunged after the war began 10 months ago and the territory has become a breeding ground for the virus, aid groups say. Hundreds of thousands of displaced Palestinians are crowded into tent camps lacking clean water or proper disposal of sewage and garbage.

To avert a widespread outbreak, aid groups are preparing to vaccinate more than 600,000 children in the coming weeks. They say the ambitious vaccination plans are impossible, though, without a pause in the fighting between Israel and Hamas.

A possible cease-fire deal couldn’t come soon enough.

“We are anticipating and preparing for the worst-case scenario of a polio outbreak in the coming weeks or month,” Francis Hughes, the Gaza response director at CARE International, told The Associated Press.

The World Health Organization and UNICEF, the United Nations children’s agency, said in a joint statement Friday that, at a minimum, a seven-day pause is needed to carry out a mass vaccination plan.

The U.N. aims to bring 1.6 million doses of polio vaccine into Gaza, where sanitation and water systems have been destroyed, leaving open pits of human waste in crowded tent camps. Families living in the camps have little clean water or even soap to maintain hygiene and sometimes use wastewater to drink or clean clothes and dishes.

At least 225 informal waste disposal sites and landfills have cropped up around Gaza — many close to where families are sheltering, according to a report released in July by PAX, a Netherlands-based nonprofit that used satellite imagery to track the sites.

Polio, which is highly contagious and transmits mainly through contact with contaminated feces, water or food, can cause difficulty breathing and irreversible paralysis, usually in the legs. It strikes young children in particular and is sometimes fatal.

The aid group Mercy Corps estimates some 50,000 babies born since the war began have not been immunized against polio.

WHO and UNICEF said Friday that three children are suspected of being infected and that their stool samples were being tested by a laboratory in Jordan.