If eredicating malaria or other deseases gives people the right to take other people's land, then European countries should go back to Africa and reconquer their old colonies. When the Belgians invaded Congo in the late 1800's there were no Congolese. There were indigenous people living on the land without any title deeds or nationality. The Belgians bought land from local village elders who sold them land that didin't belong to them, very much like what happened in Palestine when the first Jewish settlers moved in. The Belgans also tried to eredicate tropical deseases and claimed to develop a country that otherwise was still part of the dark ages. The invented people called Congolese fortunately got their independence and self-rule just like many other African countries during the 1960's. No one denies their right to exist. As for your claim that it were the Jews who worked the land: you might want to inform yourself about the thousands of Arab villages that were erased or turned into Jewish villages soon after Israeli independence. These things are well documented, you just have to be willing to see them.
UN: Gaza could be 'uninhabitable' by 2020 if trends continue (AP)