Cover up?
I don't think so. I just think the media got overly excited and started floating rumors that started God knows where. It is also likely that they reported the deaths so often that folks started counting the same ones again and again, thus inflating the numbers. I'm not surprised there were some natural deaths in the Superdome. It had been announced at the very beginning as an evacuation location for Special needs and the elderly, two groups who are in fragile health at the best of times.