Even if it is currently possible to predict most natural disasters and minimize their consequences, major social impacts have nevertheless been observed in recent decades. In this essay, a natural disaster is defined as a natural event that exerts adverse effects on human society, including those caused by geological factors and infectious organisms. It can have a wide variety of consequences, but only the most significant of these will be examined, including disaster casualties, public health crises and economic depression. First, the most direct and immediate impact of a natural disaster on society is the loss of human life. In some types of natural disasters, large numbers of casualties may not occur, but in the scenario of a large-scale flood and earthquake, the death toll could be immense. The 1976 Tangshan earthquake is estimated to have caused more than 750,000 deaths, making it the first earthquake of the 20th century (BBC, year unknown, Internet). This figure indicates a correlation between population density and a higher number of victims. Furthermore, on April 20, 2011, Edmond Mulet, head of the United Nations mission in Haiti, declared that "this marked the 100th day since the devastating earthquake that struck Haiti, killing between 250,000 and 300,000 people." (2010, cited in The Telegraph, Internet). As Haiti is an underdeveloped country, the mitigation system is incomplete, as is the extent of assistance, hence the high death toll. Additionally, it was reported that almost a month after a disastrous earthquake triggered the tsunami along Japan's northeastern coast, around 15,000 people were still missing, the majority of them are perhaps...... middle of paper..... .eid, AH, Lourens, RM, Wang, R., Jin, G. and Fanning, TG (2005) "Characterization of polymerase genes of 1918 influenza virus » Nature 437 (7060), 889-893.http://www.nature.com/nature/journal/v437/n7060/suppinfo/nature04230_S1.html (Accessed 16 April 2011) The Sydney Morning Herald (2011) “Japan races to find tsunami dead” April 7 http://news.smh. com.au/breaking-news-world/japan-races-to-find-tsunami-dead-20110407-1d5zm.htmlThe Telegraph (2010) “Haiti earthquake death toll revised to at least 250,000” http ://www.telegraph. co.uk/news/worldnews/centralamericaandthecaribbean/haiti/7621756/Haitis-earthquake-death-toll-revised-to-at-least-250000.html (Accessed 16 April 2011)Waring, SC and Brown, BJ 'The Menace of communicable diseases following natural disasters: a public health response, management and response to disasters 3(2), 41-47.