ISLAMABAD (Reuters) - Rebuilding Pakistan after the worst floods in decades could take five years, and foreign donors are in danger of reacting too slowly, a top Red Cross official said on Sunday. Crops are gone. Infrastructure is gone, including canals. Community canals. Irrigation canals. To bring that back is going to take a long time. It could end up being five years, said Bekele Geleta, Secretary-General of the International Federation of Red Cross and Red Crescent Societies (IFRC). The floods have affected 20 million people, killed up to 1,600 and left 2 million homeless. Popular anger is rising fast. Geleta said the international community must not measure the urgency of the disaster by the death toll, and that only a quarter of the required emergency aid had arrived. Swollen by torrential monsoon rains, major rivers have flooded Pakistans mountain valleys and fertile plains, wiping out villages and destroying bridges and roads. An area roughly the size of Italy is affected. But only a quarter of the $459 million aid needed for initial relief has arrived, according to the United Nations, which has warned of a second wave of deaths among the 6 million people who still need food, shelter and water and medicine. If this is not available in sufficient quantities soon, say a month or two months, then there could be a serious problem. Diseases and death, especially children, the elderly, Geleta told Reuters in an interview. We are not yet sure if there is sufficient commitment from governments. Now, and a longer-term commitment. In addition, the global public will have to be made aware, to contribute, to participate. Waterborne diseases will be coming. There is no question about it. Malnutrition will come. No question about it. Geleta, who is from Ethiopia, compared the situation in Pakistan to a famine, where governments might not take serious notice until it was too late, and international media attention could wane. Governments expect the community may have some resilience and local governments should be able to take care of. The feeling is that the country will get over it, he said. This is not a situation where the country can get over it. This is far beyond a country like Pakistan, he said. We expect the media not to scrap this disaster from the headlines for some time to come. Geleta toured flood-hit areas where high-water marks were almost at roof-level, and saw little to cheer him. You rarely even see children smiling. Usually when children see foreigners, when they see cars driving around, you see them coming waving, he said.