With cases of H3N2v influenza on the rise, a look at where we stand and the key role of our system of food animal production in strengthening viruses
The CDC has announced a sharp spike in cases of swine-origin influenza, sometimes known as "swine flu." At least 224 cases have occurred since mid-July, mostly in children living in Indiana and Ohio. This compares with just 12 cases reported nationally in all of 2011. The threat of pandemic influenza may not be imminent, but it is real.
To spark a pandemic, an influenza virus in another species must evolve the ability to infect humans and then spread quickly. So far, we believe those who contracted swine flu this year to have been infected by pigs at agricultural fairs; transmission between humans has not yet been reported. Several developments have made this more likely to occur, though -- including the serious threats introduced by the industrialization of food animal production, which selects for genes that may allow influenza viruses to reach pandemic proportions.
In a country of more than 300 million people, 224 people with a mild flu may seem unremarkable. Viruses evolve quickly, though, and one that develops the ability to infect and spread among humans could wreak havoc. In 2009, another influenza virus infected at least 1.6 million people and killed at least 19,000 worldwide. In 1967, the "Hong Kong flu" killed at least one million people around the globe. The infamous 1917-18 influenza contagion claimed at least 50 million lives.