How did Swine Flu exists?

The 2009 swine flu pandemic, also known as the H1N1 pandemic, was a global outbreak of a new strain of influenza A virus subtype H1N1. The virus was first identified in Mexico in April 2009 and quickly spread to other parts of the world, eventually becoming the first influenza pandemic of the 21st century.

The 2009 H1N1 virus likely originated from a reassortment of genetic material from swine, human, and avian influenza viruses. Reassortment occurs when two or more virus strains infect the same host cell and exchange genetic material. In this case, a swine flu virus that was circulating in North America may have reassorted with a human flu virus and an avian flu virus, resulting in the emergence of a new strain of H1N1 virus that was able to infect humans easily.

The 2009 H1N1 pandemic spread rapidly because it was a novel virus to which humans had no prior immunity. It was also particularly contagious, with infected individuals able to transmit the virus to others even before they developed symptoms. As a result, the virus spread quickly throughout the world, causing widespread illness and economic disruption.

The 2009 pandemic eventually caused an estimated 12,461 deaths in the United States and up to 284,500 deaths worldwide. However, the actual number of deaths may be higher as many cases were never diagnosed or reported.

In response to the pandemic, public health officials in many countries implemented measures to try to slow the spread of the virus, such as school closures, travel restrictions, and mass vaccination campaigns. Eventually, the pandemic ended in late 2010 when the virus had become less virulent and most people had developed immunity to it.