A logistics base at the Rafah border crossing that is vital to aid distribution has become harder to operate because 8,000 displaced people are sheltering at it.
Letter organized by Israeli rights group Shurat HaDin blames International Red Cross for repeating its failures during the Holocaust and abandoning Jewish victims.
The mother and daughter from Evanston, Illinois were transferred to Israeli territory.
The doctors who call themselves the Hostages and Missing Families Forum has sent a list of the illnesses the hostages suffer.
"With a military siege in place, humanitarian organizations including the ICRC will not be able to assist such a massive displacement of people in Gaza," ICRC said in a statement.
The ADL, Jerusalem Center for Public Affairs, NGO Monitor, Middle East Forum, and StandWithUs are among the signatories of the open letter.
Parents bringing their children to swimming classes for the first time are surprised to see Tattar standing on two crutches.