Sunday, November 06, 2005

Weekly BlogScan: Flu Shots and Fears

Someone I love is ailing right now. Each year, my spouse declines the opportunity to get a flu shot, because "it always gives you the flu." And since my better half is rarely ill, perhaps this is the right approach. I, on the other hand, get a flu shot every year about this time, and though I often get sick in the winter, it's not flu—can't be, you see, since I got a flu shot!

Who should get a flu shot? According to the Official Google Blog (powered by Blogger, of course!) and Google staff doctor Taraneh Ravazi, M.D., the answer is:
Generally, those wanting to reduce their chance of getting sick. It's especially recommended for... People aged 50 and older... Women who are or will be pregnant during the flu season... Adults and children 6 months and older with chronic heart, or lung conditions including asthma, metabolic diseases such as diabetes, chronic kidney disease, or weakened immune system such as with HIV or with medications, and any kind of brain or spinal cord disorders... Children 6 months to 18 years who are on long-term aspirin therapy... All children 6-23 months of age... All the contacts of people in these high-risk groups.

Anyone notice that the last category is the kitchen-sink option? The good doctor provides a Flu Clinic Locator to find where you might be able to get a shot. By the way, he offers this argument for my spouse's objection: "A flu shot, made from an inactivated vaccine... contrary to popular belief cannot give you the flu."

But is this the vaccine that will prevent illness of the avian flu (H5N1) variety? Likely not. The shot that works (to some degree) against human H5N1 infection is Tamilflu, a post-infection treatment (for flu you've already come down with). The vaccines being distributed at your local flu shot clinic are likely to be Fluzone and Fluarix instead. Luckily for humans, it's actually quite hard to catch avian flu—it hasn't quite made the jump to human-to-human transmission. Yet.

Flu infections run in cycles, according to the theory of rhythmicity of antigenic shift.
The annual flu cycle is likely due to a combination of mutation rates, incubation times (how long it takes before an infected person begins shedding the virus), and seasonal variations in climate.... The influenza virus also has a cycle that spans tens of years. This occurs when it undergoes "antigenic shift."... For instance, the Spanish flu pandemic of 1918 claimed over 20 million lives worldwide. These pandemics recur about every 10 to 30 years. The longer cycle is probably due to the low probability of having two different strains transfer genetic material to create a pathogenic virus and of having this new virus jump the species barrier back into humans.

We're concerned about avian flu, not because it is now threatening us, but because it satisfies two conditions for a potential pandemic: a highly mobile vector (migratory birds), and a viral similarity to the cause of several global flu pandemics. ("Both the 1957-58 and 1968-69 pandemics were caused by viruses containing a combination of genes from a human influenza virus and an avian influenza virus. The 1918-19 pandemic virus appears to have an avian origin.")

Mariane Szeto takes a more personal look at flu vaccines in Diary of a Diabetty, pointing out that being sick can raise your blood sugars. She counsels other diabetics not to gamble with flu, but to plan strategically for the ways in which flu will impact their lives.
Make sure that you consult your doctor for a "sick day plan." This may include checking your blood sugars more frequently, checking for ketones in your urine, or weighing yourself to monitor for excessive weight loss (sometimes an indicator for high blood sugars)... Don't wait! Get your flu shot as soon as possible because being sick is just no fun.

If you're fond of the eco-thriller of the Outbreak or Hot Zone variety, I recommend the trenchant future-blog of the Avian Flu Pandemic of 2006 published on the Nature Website. "Sally O'Reilly's Blog" was actually written by Nature senior reporter Declan Butler, and it's a scary read.
2 February 2006 The virus spreads Today, I was at a press conference at the National Institutes of Health in Bethesda. A guy from the CDC pointed to a giant screen, a map of the world dotted with red pixels. He said that they'd reckoned the virus might hit in two or more waves up to eight months apart, as in past epidemics. They'd hoped the first pandemic strain of H5N1 might be poorly contagious, and come back again with a vengeance after it had picked up more infectivity. By that time we might have had a vaccine. That was just a hunch, though. And it was wrong... Look at that map! With the huge increase in passengers travelling by air, it's already lodged in 38 cities around the globe. The outline of Asia is barely visible beneath the swarm of red pixels.

SCIAM Observations gives us the editors' take on articles that appear in Scientific American. In a recent post, "Don't Fear the (Bird) Reaper?," John Rennie, the magazine's editor-in-chief, takes issue with the down-play of avian flu dangers because the strain is currently only fatal to 2 to 3 percent of those infected.
we don't need H5N1 to be highly and quickly lethal. We only need it to be highly transmissible, which is advantageous in evolutionary terms. The 1918 virus, for example, had a case-fatality estimated to be "only" two or three percent, but when you have infected a significant portion of the world's population (immunologically naive to H5N1), 2% is quite a lot of dead people. Thus if there is a 40% infection rate (perhaps comparable to 1918), we would have 2.4 billion infections, very few (percentage-wise) fatal. But a 2% case-fatality rate (no one's idea of super lethality) is still 50 million deaths... In addition, influenza is infectious before symptoms (and hence incapacitation) occur, unlike SARS or Ebola. Orent likes to say that the reason wild ducks are only mildly affected is that dead ducks don't fly. But infectious people do fly—on airplanes.

Dr. Joseph Mercola, however, cries fowl on the whole idea of a Bird Flu pandemic. In "Avian Flu Epidemic Scare is a Hoax" he argues that the media and government are conspiring to "scare you into taking the flu vaccine... Dr. Henry Miller, former director of the Office of Biotechnology at the FDA, seeks to frighten the US public by telling us that the avian flu virus can jump from birds to humans and produce a fatal illness in 50% of those infected."

Dr. Mercola has his own brand of Lydia Pinkham's to peddle, though, so I'll take his advice with a grain of salt—and a flu shot.

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