1998 US outbreak in swine

In 1998, swine influenza was found in pigs in four states. In one year, it has spread through pig populations in the United States. Scientists have found that this virus arose in pigs as a form of recombinant strains of influenza in birds and humans. This epidemic has confirmed that pigs can serve as a crucible when new influenza virus due to the reassortment of genes from different strains.
 

2007 Philippine outbreak in swine

On 20 August 2007 Department of Agriculture investigated the officers home (outbreak) of swine influenza in Nueva Ecija and Central Luzon, Philippines. The mortality rate is below 10% for swine flu, unless complications such as classical swine fever. On 27 July 2007, the Philippine National Meat Inspection Service (INM) has raised the classical swine fever "red alert" warning over Metro Manila and 5 regions of Luzon after the spread of the disease to rear pigs in Bulacan and Pampanga Even if these results are negative for the virus of swine influenza.

2009 outbreak in humans

The 2009 flu epidemic is caused by a new strain of H1N1 subtype was not reported in pigs. In late April, Margaret Chan, the World Health Organization director general, said a "public health emergency of international concern" under the rules of the new WHO International Health Regulations when the first case of H1N1 virus were reported in the United States. After the outbreak, on 2 May 2009, it was reported in pigs on a farm in Alberta, Canada, with a link to the epidemic in Mexico. The pigs are suspected to have taken this new virus strain from a farm worker who recently returned from Mexico, then showed symptoms of a flu syndrome. These are probable cases, pending confirmation by laboratory tests.

The new strain was originally described as a reassortment of at least four strains of influenza A virus subtype H1N1, a strain which is endemic in humans, an endemic in birds, and two endemic in pigs. Subsequent analysis suggested that this reassortment of two strains, both in swine. Although initial reports of the new strain is identified as swine influenza (ie, a zoonosis, from swine), its origin is unknown. Several countries have taken precautionary measures to reduce the risk of a global pandemic of the disease. Swine influenza was compared to other types of influenza virus in terms of mortality: "the United States, it appears that 1000 people are infected, about 40 people require admission to hospital and approximately one person dies. "

Transmission

 Transmission between pigs

Influenza is very common in pigs, with nearly half of breeding pigs were exposed to the virus in the United States. Antibodies to the virus are also common in pigs in other countries.
The main route of transmission is by direct contact between infected animals and uninfected. These close contacts are particularly common during the transport of animals. Intensive agriculture in May also increase the risk of transmission, such as pigs are raised in close proximity to each other. The direct transfer of the virus probably occurs in pigs, or touching the nose or through dried mucus. Airborne transmission  by aerosols produced by pigs coughing or sneezing are also an important means of infection. The virus spreads rapidly, usually through a herd to infect all pigs within a few days. Transmission in May also occur through wild animals such as wild boar, which can spread the disease between farms.