It was just a week ago that a surge in coronavirus cases in the Gaza Strip, the worst there since the pandemic began, appeared to be finally waning.

Confirmed infections and deaths, at record levels in April, had declined. And Hamas, the Palestinian militant group that rules Gaza, had eased public health restrictions, even as some coronavirus hospital wards remained stubbornly crowded.

But Israel’s military assault on Gaza — launched Monday in response to rocket fire from the territory as wider tensions flared in Jerusalem — is threatening to undo those fragile gains against the virus. The fighting could cripple the enclave’s overstretched health-care system, aid agencies warn, helping seed new coronavirus outbreaks amid the chaos of war.

At least 103 Palestinians have been killed and more than 580 injured in Israeli strikes on Gaza, according to the Health Ministry. High-rise apartment buildings, factories and militant hideouts in the territory, which is hemmed in by an Israeli-Egyptian blockade, have been destroyed in the air raids.

The violence has had an immediate effect: Medical facilities, triaging the flood of new injuries, have for the most part paused coronavirus testing and vaccinations, humanitarian workers say. And a crop of hospitalized covid-19 patients who were nearing recovery were released over the past two days to make room for the growing number of war wounded.

“Gaza’s streets are empty except ambulances rushing to transfer wounded and dead people to hospitals and health centers. Medical staff are not right now able to fight covid-19,” said Raja Musleh, Gaza program director for MedGlobal, a U.S.-based humanitarian group.

A prolonged conflict between Israel and Hamas would have devastating humanitarian consequences, including for Gaza’s ability to combat the pandemic in the long term, aid workers say. The territory of about 2 million people already faced critical shortages of basic medicines, medical equipment and qualified hospital staffers.

“Even before the pandemic, Gaza faced serious systemic issues impacting the quality of health care available for its population . . . and covid-19 put the already fragile health-care system on edge,” said Suhair Zakkout, a spokeswoman for the International Committee of the Red Cross in Gaza.

If the conflict intensifies, Gaza’s health-care system “will not be able to cope,” Zakkout said. “More wounded and more covid-19 patients will likely bring it to, or close to, a total collapse.”

Gaza has reported more than 103,000 coronavirus infections and at least 930 deaths since the pandemic began last year, according to the World Health Organization. The most recent outbreak emerged in March, when a more contagious variant first identified in Britain began ripping through Gaza’s densely packed neighborhoods, leading to record numbers of hospitalizations and deaths.

The Hamas-run government imposed a nighttime curfew, banned pedestrian and vehicle traffic, and closed shops and markets. The curbs were relaxed this month.

While infections in Gaza appeared to have peaked, the WHO said last week that the covid-19 positivity rate was still as high as 28 percent. On Thursday, MedGlobal said 330 polymerase chain reaction, or PCR, tests were processed in Gaza, 92 of which returned positive results.

The outbreak in the Palestinian territories, including Gaza, “is amongst the worst in the world . . . with caseloads both astronomical and deeply underreported,” said Sasha Muench, director for the Palestinian territories for the U.S.-based humanitarian group Mercy Corps.

Last week, just before tensions flared, nearly half of Gaza’s intensive care beds were occupied by covid-19 patients, according to the WHO. And the United Nations says that just 39,000 people in Gaza have received at least one coronavirus vaccine dose, out of the roughly 100,000 doses that have reached the territory.

“The vaccine rollout has stopped” because of the fighting, the ICRC’s Zakkout said.

A vaccine shipment for Gaza from the U.N.-backed Covax initiative was paused Thursday over safety concerns.

“At the moment, no goods or people can enter Gaza because the border crossings are closed. This means no medical supplies, including vaccines, can enter,” Muench said. “In addition, no fuel to run the generators can enter, and Gaza authorities are warning of increased blackouts, including at hospitals, and potentially having no electricity in Gaza at all within a few days.”

Power outages at Gaza hospitals could interrupt oxygen supply both for covid-19 and trauma patients, health workers say.

Another concern is that new virus clusters will emerge as families, displaced by the bombings, seek refuge with relatives or neighbors. In Gaza, most families live in large, multigenerational households, often crammed into single buildings.

"Because of this, social distancing and covid-19 prevention measures were undermined," said Alaa Alkhatib, MedGlobal's program manager in Gaza. "There is tremendous overcrowding at hospitals."

Even if the violence ebbs, “the priority is obviously tending to the emergency situation and then trying to pick up the pieces,” including restitching Gaza’s pandemic response, said Hellen ­Ottens-Patterson, head of mission in the occupied Palestinian territories for Doctors Without Borders.

“We don’t know how long things are going to last, what condition the health system is going to be in afterwards and what kind of casualty numbers we’re going to be seeing,” she said.