To be declared a
pandemic, must be under three conditions:
a) The emergence of a new disease;
b) The disease
must be caused by an infectious agent;
c) The infectious agent is transmitted from human to human in multiple countries in multiple regions.
The viral
pandemics are especially difficult to combat because of the large capacity of virus mutation, which makes its control and prevention a difficult task and not always successful.
Influenza, also known as flu, is a viral disease that was possibly acquired through human contact with domesticated animals.
It is thought that most pandemics have originated in China, where traditional agriculture causes the birds, pigs and humans are in close contact, which provides a "laboratory" for new natural virus recombinants influenza.
Pandemics that affected mankind throughout history:
The first known
Pandemic was the "Justinian Plague, which killed millions of people in the Byzantine Empire, between the VI and VIII and a second wave, between the fourteenth and seventeenth centuries, killed more than 30% of the population (25 million dead).
1817 - Cholera - The first "global epidemic" documented cholera spread from Southeast Asia to the rest of the world. Followed 7 waves pandemic.
1824-1840 - Smallpox - A disease caused by virus "orthopoxvirus" reappeared in 1824 and spread throughout much of Europe after the cause 827 thousand deaths in Russia between 1804 and 1810. A further increase in the number of cases was registered during the Franco-Prussian War (1870-1871), causing more than half a million deaths. Successive vaccination campaigns allowed its total eradication in 1979.
1855 - Black Death - The third plague pandemic arose in China, caused by the bacterium Yersinia pestis and transmitted by rodents. Extended the world and in India alone, killed ten million people by the end of the century.
In the twentieth century on record, three influenza pandemics, which had the unfortunate effect of causing millions of deaths but they were also driving the great advances that have occurred in the area of microbiology, biotechnology and healthcare isolation.
During the First World War, which killed more than 9 million soldiers in the various fields of battle, the sanitary conditions were degraded and overcrowded barracks. At the end of the war, 1918-1919, many soldiers were infected by the flu, which became known as Spanish flu or pneumonic plague. The conditions were favorable for this outbreak also spread rapidly and become a pandemic. Besides Europe, the Spanish flu hit areas as far away as Alaska, Australia, China, South Africa or Northern Norway. The number of deaths from the disease has far surpassed the number killed on the battlefield. It is estimated that approximately 20 to 40% of the world population has fallen ill and have hill of 40 to 50 million people. The disease, caused by a strain called H1N1 subtype of swine influenza virus is known as "Spanish flu" because only the Spanish media published stories about it.
In 1957 came the "Asian Flu". The H2N2 virus made its first victims in China, where it was first isolated. In two months, the disease spread to Hong Kong, Singapore, India and throughout the East. Then came from Africa, Europe and, finally, the United States. A second wave of infection began in 1958. More than one million people died.
The Hong Kong flu in 1968-1969 was the third pandemic of the last century. The strain of the H3N2 subtype emerged in China in July 1968 and moved to Hong Kong, then to the USA, Europe, Southeast Asia, Japan, South America and Africa. WHO figures suggest that one million people died.
On 11 June 2009, the Influenza caused by H1N1 virus, was declared the first pandemic of the century by the World Health Organization (WHO), over one that is in addition to these sorts of outbreaks that have affected mankind throughout history , whose outcome will see on site.