Sep 15, 2009

- H1N1: Just Another Flu?

(from recent  news reports)..

It has been five months since the A(H1N1) influenza virus -- aka the swine flu -- climbed to the top of the global media heap, and with the start of the Northern Hemisphere's annual flu season just around the corner, the topic is worth revisiting.

If you take only one fact away from this analysis, take this: The U.S. Centers for Disease Control and Prevention (CDC) believes that hospitalization rates and mortality rates for A(H1N1) are similar to or lower than they are for more traditional influenza strains. And if you take two facts away, consider this as well: Influenza data are incomplete at best and rarely cross-comparable, so any assertions of the likelihood of mass deaths are little more than scaremongering bereft of any real analysis or, more important, any actual evidence.


There are a few key characteristics that differentiate this year's A(H1N1) strain from other influenza viruses. Most notable is the fact that the demographic normally associated with influenza vulnerability -- the elderly -- is considered at low risk from A(H1N1), and there has yet to be a single outbreak at any nursing home. Instead, the virus seems to have an affinity for the younger population, with higher infection rates than normal for those 24 years of age and younger, particularly those less than two years old and pregnant women. This higher incidence among the younger population could have a higher than normal disruptive impact on the labor force, when children and parents stay home from school and work. As a result of this new virus, the U.S. government has radically increased the pace of its vaccination program, and A(H1N1)-specific vaccinations will begin in October.

These differences, however, are not game changers. So, while the flu will pose a significant logistical and public relations challenge to governments seeking to prevent outbreaks and control the virus' spread, there is no indication that A(H1N1) will cause even a shadow of the disruption that the hysteria of months past suggested.

Most of that hysteria was rooted in the memory of the 1918 Spanish influenza. Although estimates vary widely -- remember that the world was in the fifth year of a grinding war when the epidemic hit, so bean-counting was not exactly high on the priority list -- most agree that between 50 million and 100 million people perished from the 1918 flu globally, including roughly 500,000 Americans.

The Spanish influenza was particularly frightening because it disproportionately struck down people in their prime -- adults in the 25-35 age cohort -- in addition to the very young and very old (the prime sufferers of traditional influenza viruses). Based on numbers reconstructed from that period, 28 percent of the American population contracted the Spanish influenza, of which 1.4 percent to 2.3 percent perished (or 0.39 percent to 0.65 percent of the population). The 1918-1920 influenza outbreak represents the only time during the 20th century when the U.S. population declined.

There are many unknowns about the A(H1N1) swine flu that are circulating around the world, but with five months of data to draw from, there are some clear manners in which A(H1N1) is not comparable to the 1918 Spanish flu.

Most notable is the mortality rate, or more to the point, the lack of a mortality rate. Global data is sketchy to say the least, but as of Sept. 4, the World Health Organization (WHO) had linked only 3,199 deaths globally to A(H1N1). In the United States, where data is more reliable, the figure is 593, a far cry from the 402,000 to 675,000 American deaths of the 1918 epidemic.

Within the United States, the data STRATFOR finds most complete comes from New York City, one of the most immediately impacted regions when A(H1N1) erupted in April. The city's health department estimates that 800,000 people -- 10 percent of the population -- contracted the virus in the early weeks of its spread. But so far only 930 required hospitalization and only 54 have died. 

Bottom line: While A(H1N1) is as communicable as the traditional flu strains, it has shown no inclination to be more deadly. In fact, from what can be discerned from the New York City data, the mortality rate lingers on the edge of the statistically insignificant -- a 0.00675 percent mortality rate among those contracting the virus, translating into a 0.00064 percent mortality rate among the general population.

Reporting the statistics like this is admittedly somewhat skewed. Any death tolls attributed to the A(H1N1) flu naturally cover only the period since A(H1N1) was identified in April. They do not cover the (as yet unfinished) year and obviously do not include any data about the upcoming Northern Hemisphere's annual flu season, which will undoubtedly result in many more flu-related deaths. Nor do the statistics include data from other influenza viruses.

More infections and deaths are sure to follow -- as winter sets in, the rate will increase. And there is always the chance that A(H1N1) will mutate into a more deadly strain -- in fact, this is precisely what occurred with the 1918 Spanish influenza virus. But, at present, neither the WHO nor the CDC appears to suspect that A(H1N1) is any more deadly than any other seasonal flu.

The critical factor to bear in mind is that all strains of influenza claim thousands of lives every year. In the United States, on average, some 36,000 people die of flu every year - 1,100 in New York alone. Globally, deaths related to influenza are estimated to range from 250,000 to 500,000 people per year. So far this year, only about 3,000 people have died worldwide in relation to the A(H1N1) outbreak, and most of those deaths occurred during the flu season in the Southern Hemisphere. From a statistical perspective, at present, A(H1N1) nearly falls into the range of background noise


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