“We want the government to do everything possible to bring the hostages back — that has to be the top priority,” Tomer Keshet, Mr. Bibas’s cousin, said in an interview. “Yarden is wounded, and the baby isn’t even standing yet, he is barely crawling.”

“We are so worried that the children were separated from their parents, that they are frightened, that they don’t have the right things to eat, and that that could have long-term repercussions,” Mr. Keshet said. “They are being held underground, hungry, not knowing what’s going on, hearing bombing and fighting and shouting in a language they don’t understand. We don’t know what condition they are in, or what condition they will be in when they come back, after this emotional trauma.”

Although physicians generally refrain from discussing their patients’ medical conditions out of respect for privacy, several personal physicians of the hostages spoke out publicly last week to draw attention to their plight and stress the urgency of their situation.

“In some cases, children were taken moments after watching their parents being brutally murdered,” said Dr. Zion Hagai, chairman of the Israel Medical Association. “They are not only forced to live with this trauma but to experience it in a strange, dark and scary place.”

Speakers highlighted the cases of several particularly vulnerable hostages, among them Raz Ben Ami, 57, from the Be’eri kibbutz, who was being treated for neurosarcoidosis, a serious and rare disease that affects the brain, spinal cord or peripheral nerves, causing hearing and vision loss, confusion, agitation and other effects.

Dr. Arnon Elizur spoke of a young patient, Yagil Yaakov, who has a life-threatening peanut allergy and could die in minutes if he were exposed to even trace amounts of peanut powder. Islamic Jihad, another militant group in the Gaza Strip, recently published a video of the boy, looking pale and thin, with dark shadows under his eyes.

“I can’t imagine what is going through his mind when he is served food,” Dr. Elizur said. “Can he be certain it doesn’t contain trace amounts of peanuts? Every meal for him is like playing Russian roulette.”

The son of another hostage, Haim Peri, said that his father had advanced heart disease.

“He is an artist, a peace activist and a man who always fought for human rights,” said the son, Noam Peri. “He is a brave man, but at age 80, he is not a healthy man, and requires daily medications. He will not survive captivity for long.”