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August 25, 2009

Will This Fall Be The Second Wave of Swine Flu?

The Humane Society of the United States

by Michael Greger, M.D.

According to the World Health Organization, swine flu has spread with "unprecedented speed" to 168 countries since its emergence. What took past pandemics more than six months to spread around the globe, the swine-origin H1N1 virus accomplished in under six weeks.

Though swine flu has likely infected more than a million Americans, the virus got a late start. For reasons still not well understood, flu viruses thrive best in the wintertime. Swine flu's emergence in the spring likely limited transmission in the Northern hemisphere in the ensuing summer months, leaving most people susceptible for the upcoming flu season.

This leaves officials concerned that there may be a resurgence of the virus this fall in the northern hemisphere, before a vaccine is widely available.

Cause for Concern

In a world in which millions continue to die of scourges such as AIDS and tuberculosis, though, why is there so much concern about this so-called swine flu? Because the last time a nearly entirely new flu virus apparently jumped species and triggered a pandemic, it went on to become the deadliest plague in human history, the influenza pandemic of 1918.

Still, only about 1000 people have died so far from swine flu. Although any virus that kills scores of children can hardly be described as "mild," the current pandemic has not been much worse than the regular seasonal flu so far, but this may just be the first wave.

The 1918 pandemic was apparently relatively mild, too—at first. Compared to what was to come later, the first "wave" in summer 1918 hardly registered a blip, but then in the fall it started killing tens of millions of people.

Nightmare Scenario

The "nightmare" scenario, especially as H1N1 spreads into Southeast Asia, would be if the swine flu were to combine with the H5N1 bird flu, both of which have been found in pigs.

Should a pig become co-infected with both the new swine flu and bird flu, the concern is that it could theoretically produce a virus with the human transmissibility of swine flu and the human lethality of bird flu, which has officially killed more than half of its confirmed human victims.

Pandemic Prevention

Once a pandemic virus emerges, it is nearly impossible to stop. Swine flu has evolved into the first pandemic of the 21st century and almost certainly will not be the last. Attention must therefore be turned to preventing the emergence of viruses with pandemic potential in the first place.

The industrialization of poultry production has been blamed for the unprecedented changes taking place among bird flu viruses in recent decades. Similar changes in the pig industry have likely contributed to the emergence of the current pandemic, as documented in our upcoming video feature Flu Factories: Tracing the Origins of the Swine Flu Pandemic.

Dr. Michael Greger is director of public health and animal agriculture for Humane Society International.

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