After 11 Months of War, Gaza Faces a New Threat: Polio

War and disease have been cruelly intertwined for as long as humans have confronted one another on the battlefield, and in the Gaza Strip, polio is now stalking a population that for nearly 11 months has been on the run from relentless bombardment.

Under ratcheting international pressure to prevent an outbreak of the crippling disease, Israel, which has rebuffed much of the criticism of its handling of the war, is moving with relative haste. Israeli officials agreed this week to temporary and localized pauses in fighting to allow United Nations aid workers to deliver vaccines to 640,000 children.

In a conflict where the warring sides have agreed on precious little, Hamas says it will also abide by the staggered pauses in fighting, which are scheduled to begin on Sunday.

But health officials warn the plan comes with enormous challenges. Much of Gaza’s infrastructure is in ruins, hundreds of thousands of Palestinians are living in temporary shelters and aid workers have been attacked while trying to deliver supplies.

Those risks were underlined on Thursday when Israeli forces targeted part of an aid convoy in Gaza, killing four people, according to Anera, an American nonprofit that organized the trucks. The convoy was ferrying food and fuel to an Emirati-run hospital in southern Gaza and had coordinated in advance with the Israeli authorities, the nonprofit said in a statement.

The Israeli military said “armed individuals” had joined one of the vehicles in the convoy and that it had carried out a strike targeting them.

The agreement for the vaccination campaign and the pause in fighting came together six weeks after the World Health Organization first said that traces of poliovirus had been found in wastewater in Gaza. Two weeks ago, a nearly 1-year-old boy was confirmed to be Gaza’s first polio case in 25 years, lending urgency to the need for widespread vaccinations for the disease, which can cause paralysis and death.

An outbreak would add to the dire humanitarian challenges facing 2.2 million Palestinians in Gaza — and would most likely spur further international condemnation of Israel for the heavy wartime restrictions it has placed on the territory. The resurgence of the disease, which has been eradicated in almost all of the world, reflects the toll of Israeli bombardments that have destroyed Gaza’s waste and water systems.

In a sign of the global concern, Secretary of State Antony J. Blinken used a visit to Israel last week to push Prime Minister Benjamin Netanyahu to agree to the pauses, a senior U.S. official said. Mr. Netanyahu was open to brief, limited pauses, and made clear that he would not agree to a Gaza-wide cease-fire, the official said.

“I think this is a way forward,” Dr. Rik Peeperkorn, the top W.H.O. representative in Gaza, told reporters on Thursday as the agency announced the agreement on the pauses. “Not doing anything would be really bad. We have to stop this transmission in Gaza, and we have to avoid the transmission outside Gaza.”

In a sign of Israeli concern about the spread of the disease, officials there announced a week after the virus was detected that they would vaccinate their troops in Gaza. Hamas has also signaled that its leaders see an overriding need for a pause in hostilities to allow for vaccinations.

“We are ready to cooperate with international organizations to secure this campaign,” a Hamas official, Basem Naim, said on Thursday.

Israel has periodically paused fighting for humanitarian reasons during the war, including announcing that it would not attack during the daytime along a key aid route in southern Gaza to make it easier for relief convoys to move badly needed supplies into the territory. But the pauses for the vaccine campaigns are expected to last longer than previous breaks in the fighting, and will cover larger geographic areas.

The vaccinations will begin around 6 a.m. on Sunday in central Gaza and continue for at least three days, and longer if needed, Dr. Peeperkorn said. When that effort is complete, the drive will shift to southern Gaza for three days, and later to northern Gaza for three days. According to the agreement, fighting is supposed to stop in each region during the vaccination drives.

A second booster round of immunizations will need to be given four weeks after the first, and Dr. Peeperkorn said that was part of the agreement reached on Thursday. “We expect that all parties will stick to that,” he said.

The pathogen circulating in Gaza is believed to be vaccine-derived Type 2 poliovirus. Type 2 polio was removed from the widely used oral vaccines a few years ago, making many children in Gaza potentially susceptible.

The pathogen is described as vaccine derived because of the way it circulates: The oral vaccines contain a weakened form of the virus that normally does not cause illness. A child receiving the vaccine may shed the weakened virus in stools or bodily secretions.

That virus may not be harmful initially, but when vaccination rates in a population are inadequate, a vaccine-derived poliovirus may spread widely without interruption, undergoing genetic changes and eventually reverting to a type able to cause paralysis and outbreaks.

Polio vaccine coverage rates in Gaza were at about 99 percent in 2022 but have dropped dramatically since. At least 90 percent of children under 10 need to be vaccinated to stop the disease from spreading, Dr. Peeperkorn told reporters on Thursday.

The vaccination drive will come too late for a boy named Abdul Rahman Abu Al-Jidyan, who is almost a year old and living with his family in a tent in Deir al Balah in central Gaza.

He was born just before the war between Israel and Hamas began last October, and was unable to get the routine vaccinations given to babies, his mother said, because the family was constantly forced to move from one shelter to another to escape the fighting. Then, about two months ago, Abdul Rahman stopped walking and crawling.

“I found the boy vomiting, he stopped moving and had a fever,” his mother, Nivine Abu Al-Jidyan, said in an interview this week with Reuters. Exams at a hospital in Gaza and a sample sent to a lab in Jordan confirmed heath officials’ fears: He had tested positive for polio.

That the 10-month-old boy lost some of his mobility more than a month before he was diagnosed underscores the probability that the virus is circulating in Gaza. It also underscores what experts say is the urgency to vaccinate other children before they, too, are infected.

Reporting was contributed by Ephrat Livni, Raja Abdulrahim, Aaron Boxerman and Michael Crowley.