<P> In 1997 an outbreak of respiratory disease occurred in Malaysian farmers and their pigs . More than 265 cases of encephalitis, of which 105 were fatal, were recorded . A new paramyxovirus was discovered in a victim's brain; it was named Nipah virus, after the village where he had lived . The infection was caused by a virus from fruit bats, after their colony had been disrupted by deforestation . The bats had moved to trees nearer the pig farm and the pigs caught the virus from their droppings . </P> <P> Several highly lethal viral pathogens are members of the Filoviridae . Filoviruses are filament - like viruses that cause viral haemorrhagic fever, and include the Ebola and Marburg viruses . The Marburg virus attracted widespread press attention in April 2005 after an outbreak in Angola . Beginning in October 2004 and continuing into 2005, there were 252 cases including 227 deaths . </P> <P> The Ebola virus epidemic in West Africa, which began in 2013, is the most devastating since the emergence of HIV . The initial outbreak occurred in December 2013 in Meliandou, a village in southern Guinea . Among the first victims were a two - year - old boy, his three - year - old sister, their mother and grandmother . After the grandmother's funeral, which was attended by her family and caregivers, the disease spread to neighbouring villages . By March 2014 the outbreak was severe enough to raise the concern of local health officials who reported it to the Guinean Ministry of Health . By the middle of the year the epidemic had spread to Liberia and Sierra Leone . As of June 2015, the World Health Organisation reported over 27,000 cases of the disease, which had resulted in more than 11,000 deaths . </P> <P> The natural source of Ebola virus is probably bats . Marburg viruses are transmitted to humans by monkeys, and Lassa fever by rats (Mastomys natalensis). Zoonotic infections can be severe because humans often have no natural resistance to the infection and it is only when viruses become well - adapted to new host that their virulence decreases . Some zoonotic infections are often "dead ends", in that after the initial outbreak the rate of subsequent infections subsides because the viruses are not efficient at spreading from person to person . </P>

Great epidemics in history that were caused by viruses