GENEVA -- Despite a ceasefire in Gaza and an increase in aid, hunger and disease persist, putting children's lives at risk as the flow of aid remains only a fraction of what is needed, the World Health Organization (WHO) said Thursday.

"The situation still remains catastrophic because what's entering is not enough," WHO chief Tedros Adhanom Ghebreyesus told an online press briefing from the UN health agency's Geneva headquarters.

Since the ceasefire between Israel and Hamas took effect on Oct 10, he warned, there has been "no dent in hunger, because there is not enough food."

"We welcome the return of hostages, the release of prisoners, the cessation in violence and the increase in aid flows. But the crisis is far from over and the needs are immense. More than 170,000 people have injuries in Gaza ... At least 42,000 people have injuries that require long-term rehabilitation," said Tedros.

"Hunger and disease have not stopped, and children's lives are still at risk," he said. "The destruction has been physical but also psychological. An estimated one million people need access to mental health care. The demands on the health system are huge, but significant parts of the system have been destroyed or badly degraded."

"There are no fully functioning hospitals in Gaza, and only 14 out of 36 are functioning at all. There are critical shortages of essential medicines, equipment and health workers," Tedros pointed out.

Since the ceasefire took effect, the WHO has been sending more medical supplies to hospitals, deploying additional emergency medical teams, and scaling up medical evacuations.

There are still 15,000 patients who need treatment outside Gaza, including 4,000 children. More than 700 have died while waiting for evacuation, said Tedros, calling for the restoration of referrals to the West Bank, including East Jerusalem.

"We call for more countries to receive patients from Gaza for specialized care; and we call for the Rafah crossing -- and all crossings -- to be opened, to allow more patients to be treated in Egypt, and to enable the scale-up of aid," said Tedros.

The Rafah crossing was supposed to be opened last week, he said, noting that a significant amount of aid has built up at Al-Arish in Egypt that is ready to enter Gaza as soon as the crossing is opened.