The H1N1 flu, also known as swine flu, in the United States was never found to be a population-based outbreak of H1N1 swine flu until April 2009.?

Somewhere in mid-April 2009, the U.S. Centers for Disease Control and Prevention (CDC) discovered a new influenza A virus in a sample sent by a 10-year-old child in California, and it was found that the genome of the new H1N1 virus was recombined from that of the North American swine lineage of H1N1 and the Eurasian swine lineage of the H1N1 influenza virus. It is therefore called ? swine-derived influenza A virus?

The same strain of virus was then found in a sample test of an 8-year-old child. After a series of information synthesized by tracking down contacts of the two patients and checking for any link between the child and the swine, research experts suspected that human-to-human transmission of the virus was beginning to occur.

In early late April 2009, in the U.S. Morbidity and Mortality Weekly Report journal, the study in question published the CDC's description of these cases and requested that U.S. state public ****health laboratories send all samples of influenza A that could not be typed to the CDC. Within a day, three more patients were found to be infected with the new H1N1 in hospitals in San Diego County and Imperiare County, Calif. ?

The CDC then began to develop a strain of virus for use in preparing a vaccine ? candidate vaccine viruses, which were eventually selected for use in making the vaccine. It was then sent to vaccine manufacturing companies to begin producing the vaccine to prepare the government for when it was necessary to prevent an epidemic.

Since mid-April 2009, the pandemic influenza alert has been gradually increasing and a pandemic is imminent.

In June 2009, the pandemic influenza alert was raised to level 6, when 27,737 cases of influenza were confirmed in 75 countries and territories around the world,*** counting 27,737 patients diagnosed and 141 deaths.

It took about a year for the pandemic flu epidemic to essentially end, with data on the CDC's website showing that in about a year's time, there were roughly 60.8 million infections in the U.S., 274,000 hospitalizations and 12,469 deaths.

The data is huge and staggering, and after this data is the prevention, control and calculation of the flu epidemic by experts and related staff. Influenza is always a major concern.