At least 44 people, including six children, were killed in an Israeli strike on Khan Yunis, in the Gaza Strip, an official at Nasser Hospital told ABC News.

At least 90 people were injured, the hospital’s head of nursing said.

The Israeli military on Monday ordered the evacuation of part of a designated humanitarian zone in Gaza. The military said it will begin an operation against Hamas militants who are in the area and use it to launch rockets toward Israel.

The deadly strike in Khan Yunis began Sunday night before the evacuation order was announced.

-ABC News’ Somayeh Malekian

Poliovirus has been detected in wastewater in multiple locations of the Gaza Strip, including two major cities in the region, the World Health Organization (WHO), Gaza health and Israeli officials confirmed on Sunday.

Among the locations where the poliovirus has been found in wastewater are Deir al-Balah in central Gaza and Khan Younis in southern Gaza, two major cities where the majority of people in the war-torn region currently reside, the officials said.

WHO officials said that while they have received no reports of people contracting polio symptoms in Gaza, an investigation is underway to identify how the virus has spread. WHO said it is working with UNICEF and the U.N. Relief and Works Agency for Palestine Refugees in the Near East (UNRWA) to investigate and establish "prompt vaccination campaigns."

Polio is a highly infectious viral disease that largely affects children under 5 years of age, according to WHO's website. Since 1988, poliovirus cases worldwide have decreased by 99%, according to WHO.

The Israel Defense Forces announced Sunday that it will vaccinate all soldiers operating in Gaza to prevent the spread of poliovirus.

The IDF also said is is working with international organizations to provide polio vaccines for people in Gaza.

Dr. Tedros Adhanom Ghebreyesus, the director-general of WHO, sounded the alarm in a statement on Friday, saying, "The decimation of the health system, lack of security, access obstruction, constant population displacement, shortages of medical supplies, poor quality of water and weakened sanitation are increasing the risk of vaccine-preventable diseases, including polio."

Ghebreyesus added, "This poses a risk for children and creates the perfect environment for diseases like polio to spread."

-ABC News' Victoria Beaulé

Israeli Prime Minister Benjamin Netanyahu is expected to meet with President Joe Biden in Washington on Tuesday, Netanyahu's office said in a statement Sunday.

The meeting between the two leaders is scheduled to occur at noon on Tuesday, Netanyahu's office said.

Netanyahu's flight to Washington is scheduled to leave Israel on Monday morning, the prime minister's office said.

The meeting between Biden and Netanyahu will come ahead of the Israeli prime minister's July 24 address to a joint session of Congress.

The two governments had tentatively scheduled a meeting between Biden, who is recovering from COVID, and Netanyahu on Monday.

However, a Biden administration official on Sunday disputed that a date and time have been set for the meeting with Netanyahu, and that an exact date and time are still dependent on when the president tests negative for COVID and returns to Washington, D.C. Biden has been self-isolating in Rehoboth, Delaware.-ABC News' Victoria Beaulé and Justin Ryan Gomez

Multiple people were killed and others have been injured in an Israeli strike on oil storage facilities in the port of Hodeidah in Yemen, according to the Houthis who said the attack will "only increase the resolve [...] of the Yemeni people."

The Houthis accused Israel of an attack that "targeted civilian facilities, oil tanks and the electricity station in Hodeidah, with the aim of doubling people’s suffering and pressuring Yemen to stop supporting Gaza."

Israel said its attack came in response to over 200 projectiles that the Houthis have launched toward Israel, saying they targeted the port as as the main supply route for weapons transfers with Iran.

-ABC News' Ahmed Bader, Dana Savir and Bruno Nota