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When Swine Flu Strikes

By Drew Levin | May 1, 2009

Photo by Jonathan van Smit (CC).

Sun Tzu offers sage advice: Know your enemy. So what, exactly, is Influenza virus A subtype H1N1, commonly known as swine flu?

The letters H and N stand for hemagglutinin and neuraminidase, two kinds of protein on the surface of the influenza virus. The numbers refer to protein subtypes—small variations in structure. For example, H1N1 has a coat of the first subtype of hemagglutinin and the first subtype of neuraminidase. Hemagglutinin helps a virus attach to and insert itself into a target cell, while neuraminidase is what helps the viruses break back out and spread to other cells.

The H and N proteins are targeted by annual flu vaccines because their mechanisms are understood to play an important role in virulence. Each year's flu shots contain the scientific community's best estimate of the H1N1, H3N2, and Influenza B strains that will predominate in the coming season.

The current seasonal flu vaccine does not protect against swine flu, as its H1 is different from the typical H1 against which humans have so far been immunized. The 1918 influenza pandemic which killed an estimated 50 million people was also an H1N1 virus, but in that situation the H1 originated from a bird. Today's version is thought to be a combination of bird, human, and swine strains. Human unfamiliarity with this new swine version is troubling because lack of immunity is a primary prerequisite for a pandemic.

Earlier this week, the World Health Organization raised its pandemic alert level to 5 (out of 6), indicating widespread human infection of an animal influenza capable of causing community-level outbreaks. Two days prior, the Centers for Disease Control issued a travel advisory on April 27, advising against nonessential travel to Mexico.

America is not alone in its caution. Around the world, countries have advised against travel to Mexico, and the European Union issued—and then rescinded—an advisory against travel to the United States. The WHO Director-General issued a statement advising against closing borders, asserting that "the current focus should be on mitigation measures." There have been confirmed cases in nineteen states in the United States.

As of 2007, 46 million Americans under the age of 65 were without health insurance, potentially undermining the effectiveness of a national response to any pandemic. People who are reluctant to seek early care may not only endanger themselves but also run the risk of infecting more people. Should infections become widespread, Americans without healthcare would be at an extreme disadvantage, potentially paying through the nose for any cure or palliative. International health inequities may have a similar effect on the spread and cost of remedying a pandemic.

Coping with the current outbreak is compounded by the recent run on Tamiflu and Relenza in New York pharmacies. If swine influenza spreads, prescriptions for Tamiflu may outstrip supplies.

The CDC responded by releasing more than 11 million doses of Tamiflu from its emergency stockpile of 50 million. This new abundance, however, does not mean that people should stock up on Tamiflu "just in case"—it is meant to be taken as a reactive drug, not a proactive drug. It is most effective within 48 hours after symptoms appear, and it is not intended or able to fulfill the preventative role of a vaccine.

Given the small overall number of confirmed swine flu cases, the current situation warrants the caution associated with a normal flu season. By practicing good hygiene such as washing hands, and notifying a doctor if influenza symptoms appear, people can have an appreciable impact on the spread of swine flu. Awareness of the common symptoms is essential.


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