<P> Severe acute respiratory syndrome (SARS) is caused by a new type of coronavirus . Other coronaviruses were known to cause mild infections in humans, so the virulence and rapid spread of this novel virus strain caused alarm among health professionals as well as public fear . The fears of a major pandemic were not realised, and by July 2003, after causing around 8,000 cases and 800 deaths, the outbreak had ended . The exact origin of the SARS virus is not known, but evidence suggests that it came from bats . </P> <P> West Nile virus, a flavivirus, was first identified in 1937 when it was found in the blood of a feverish woman . The virus, which is carried by mosquitoes and birds, caused outbreaks of infection in North Africa and the Middle East in the 1950s and by the 1960s horses in Europe fell victim . The largest outbreak in humans occurred in 1974 in Cape Province, South Africa and 10,000 people became ill . An increasing frequency of epidemics and epizootics (in horses) began in 1996, around the Mediterranean basin, and by 1999 the virus had reached New York City . Since then the virus has spread throughout the US . In the US, mosquitoes carry the highest amounts of virus in late summer, and the number of cases of the disease increases in mid July to early September . When the weather becomes colder, the mosquitoes die and the risk of disease decreases . In Europe, many outbreaks have occurred; in 2000 a surveillance programme began in the UK to monitor the incidence of the virus in humans, dead birds, mosquitoes and horses . The mosquito (Culex modestus) that can carry the virus breeds on the marshes of north Kent . This mosquito species was not previously thought to be present in the UK, but it is widespread in southern Europe where it carries West Nile virus . </P> <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>

When did the problem of diseases start to develop in the history of mankind