[Infowarrior] - Don't Leap to Conclusions, WHO Warns

[Richard Forno]

Flu's True Severity Is Still Unknown
Don't Leap to Conclusions, WHO Warns

By Joel Achenbach and David Brown
Washington Post Staff Writers
Saturday, May 2, 2009

http://www.washingtonpost.com/wp-dyn/content/article/2009/05/01/AR2009050101777_pf.html

So is this new swine flu outbreak the next great plague, or just a  
global spasm of paranoia?

Are we seeing a pandemic or a panic?

The pathogen that has seized the world's attention has an official  
name (swine-origin influenza A H1N1), an acronym (S-OIV), a nickname  
(swine flu) and an apparent birthplace (Mexico). But the essential  
nature of the pathogen, its personality, its virulence, remain matters  
of frenetic investigation. Like all influenza viruses, it is mutating  
capriciously and, thus, is not a static and predictable public health  
threat but an evolving one.

The bug has gone global, having shown up in Asia yesterday with the  
first reported case in Hong Kong. It also popped up in Denmark, as  
well as in eight new U.S. states.

But there has been some flu-scare backlash, with some officials  
questioning whether schools are too quick to close their doors at the  
first hint of the virus.

The World Health Organization directly addressed the pandemic-versus- 
panic issue yesterday by cautioning the public against leaping to any  
conclusions about the virulence of the virus. It has yet to show  
lethality outside Mexico (the one person to die in the United States  
was a toddler who traveled from Mexico to Texas), though that doesn't  
mean it will remain a mild pathogen in the weeks and months to come,  
officials said.

Influenza is a simple virus, with just eight genes, but it makes poor  
copies of itself, leading to constant mutation. Most of those  
mutations are dead ends, but, given enough chances, the virus can  
become more infectious or more lethal. Although the United States is  
past its flu season, the Southern Hemisphere, where the virus has  
spread, is entering the cold months when influenza can become explosive.

Some positive news surfaced yesterday: Mexican scientists said the  
contagiousness of the swine flu is no greater than that of the  
seasonal flu that circulates every year. And a preliminary genetic  
analysis hasn't turned up any of the markers that scientists associate  
with the virulence of the 1918 "Spanish" influenza virus, said Nancy  
Cox, head of the flu lab of the Centers for Disease Control and  
Prevention.

The 1918-19 pandemic has cast a long shadow over today's health  
emergency. That virus circled the world, eventually infecting nearly  
everyone and killing at least 50 million people.

Jeffery Taubenberger, the National Institutes of Health researcher who  
reconstructed the 1918 influenza virus, said he is growing the new  
swine flu virus in his lab.

"We're very early on in figuring out what makes this virus tick. I am  
loath to make predictions about what an influenza virus that mutates  
so rapidly will do," he said. But he believes it will spread across  
the planet: "My prediction is that this strain will continue to  
spread, and it is very likely to become a pandemic virus, if it's not  
already a pandemic now. That does not mean that this has to be a very  
severe pandemic like 1918."

Michael T. Osterholm, an epidemiologist at the University of  
Minnesota, said the situation is analogous to forecasting a hurricane  
when meteorologists know only that there is a high-low pressure  
gradient in the Atlantic. "Everyone in one week wants an answer as to  
what it will do. Anyone who gives you an answer right now, do not  
listen to them about anything else because you cannot trust them,"  
Osterholm said.

WHO spokesman Gregory Hartl noted yesterday that the public may  
misunderstand the word "pandemic." The term refers to where an illness  
spreads, not its severity.

A major unknown is the swine flu virus's "case-fatality rate" -- the  
small fraction of infected people who die. For the 1918 influenza, it  
was 2 to 2.5 percent for the United States as a whole, but in military  
camps and on troop ships, the rate was a brutal 7 to 10 percent, and  
in some Inuit villages, it soared to 70 percent.

The other two flu pandemics of the 20th century, however, were far  
milder. The Asian influenza of 1957-58 had a fatality rate of 0.2-0.5,  
and the rate during the Hong Kong influenza of 1968-69 was even lower,  
about 0.1 percent, close to what it is for seasonal flu.

The case-fatality rate of the swine flu will become certain only when  
epidemiologists are able to track its behavior from the moment it  
arrives in a population -- a difficult task under the best  
circumstances, which the current circumstances in Mexico aren't.  
Physicians there first suspected something strange when a small number  
of young adults showed up in the hospital with severe pneumonia.

The question is how many other people contracted influenza but never  
got very sick. Researchers must draw blood from a sample of people in  
affected towns and cities to estimate how many people were infected  
and never knew it.

The early signs from the United States and a few European countries  
where the strain is spreading suggest it is not unusually dangerous,  
as there have been few deaths so far. If that continues to be true,  
then it may help explain the mysteriously high mortality in Mexico. It  
may be that Mexico already has had hundreds of thousands, and possibly  
millions, of cases -- all but the most serious hidden in the "noise"  
of background illness in a crowded population.

The fact that most people infected in other countries had recently  
been to Mexico -- or were in direct contact with someone who had been  
-- is indirect evidence that the country may have been experiencing a  
silent epidemic for months.

Regardless of how dangerous it proves to be, the new swine flu virus  
is almost certain to eventually infect every continent and country,  
although that may take years. Studies in the 1930s found that 97  
percent of people born before 1920 had antibodies to the Spanish  
influenza virus. That's evidence that virtually everyone alive in the  
three years it circulated -- 1918, 1919 and 1920 -- was at one point  
infected, even if they didn't know it.

A similar fate awaits any population exposed long enough to a new flu  
strain to which it has no immunity, experts believe.