Flu Update

Welcome to flu season!  Let’s review.

Influenza is a virus that affects humans and several other species that often live in close proximity to humans such as domestic pigs and birds.  The virus changes over time due to “antigenic drift”, often rendering immunity to previous strains irrelevant.  If an animal is infected with two strains, they can recombine, leading to a new and very different virus, a process called “antigenic shift” which leads to pandemics.

Influenza is horrible.  It usually strikes hard and fast, with muscle aches, cough, and fever (the usual case definition for influenza-like illness is temperature of 37.8/100.0, cough or sore throat, an no other good explanations for the symptoms).  For most people it will pass, eventually.  For some, it will damage the lungs making them susceptible to bacterial infections like  pneumonia, which can be fatal.

Last season saw the emergence of a new strain if influenza A, now called 2009 A H1N1, probably due to antigenic shift.  It rapidly became pandemic, affecting especially younger people who seemed to have little immunity for the new strain. (Also, pregnant women died at an alarming rate.)  In a normal season, it’s the elderly and people with chronic diseases who suffer the worst effects of the epidemic. There is no indication of a looming pandemic this year (although H1N1 will still probably be around), so we’re likely to have the usual unpredictable flu season.   Excess deaths due to the flu vary considerably from season to season, with best estimates of between about 3000 and 49000 deaths per year.

Each season, a vaccine is developed by tracking strains emerging in other parts of the world. The vaccine is usually quite effective at preventing flu and complications from flu, but some past seasons have seen new strains emerge after the development of the vaccine.  Vaccination is still the best way to prevent flu.

Anti-viral medications can help reduce the severity of the flu, but they’re not terribly effective.  Prevention is the best tool we have, including hand washing and other hygiene, and vaccination.

So far, only minimal flu activity has been seen in the US.  I’ve seen a few suspicious cases, but nothing confirmed.  Each year is a bit of a surprise.  I’ve gotten my shot, as has my daughter.  Supplies are good this year.  Hopefully, it will be a boring season.

18 Comments

  1. “Hopefully, it will be a boring season.”

    Ne’er were truer words spoken. We had a flu shots at work this week. I only had to ‘bully’ one of my staff (scared of needles). I need to promote the PTX booster as well. We have two new borns joining the team too

  2. We all got flu vaccines as a family on Monday. My Trophy Husband even got his Tdap booster while we were there.

    tideliar: Two? Congratulations!

  3. Samantha

     /  October 29, 2010

    Flu shotted and I got my TDaP to boot! Yay for contributing to herd immunity!

  4. Chuck

     /  October 29, 2010

    I must correct one aspect that Samantha just brought up. At best 35-40% of the US population receives the influenza vaccine during any influenza season. Herd immunity will also be reduced on a percentage basis depending on how many strains and how prevalent they are that are not covered by each year’s influenza vaccine. The best year will be 40% for the nation and it will only go downhill from there based on scientific decisions.

    • I don’t think herd immunity operates as a continuous variable

      • Chuck

         /  October 29, 2010

        Theoretical herd immunity is always in a state of flux. The theoretical percentage of the population for each contagious illness is also variable, and not a constant static amount for all illnesses or seasons.

      • Enh, I don’t see how it couldn’t function as a “continuous variable”… but it’s certainly extremely non-linear.

        Wh

        • Argh, gonna have to bug MarkCC so as that Enter goes to “Preview” instead of “Post Comment”.

          In any case, to continue: What I’m about to say is highly speculative, and of course highly dependent on the effectiveness of the particular vaccine we are talking about… but I imagine that in the 30-40% uptake range, the relationship between uptake and “herd immunity” (however you quantify it) would be fairly linear. There’s a strong near-discontinuity around (for most vaccines) 85-95%, where suddenly even the unvaccinated are mostly protected. Then of course there is a true discontinuity when the disease is eradicated…

          I wanted to say more but I’m being talked to and I can’t concentrate. So if something I said was stupid, I’m blaming it on that.

          • Chuck

             /  October 29, 2010

            James said [… but I imagine that in the 30-40% uptake range, the relationship between uptake and “herd immunity” (however you quantify it) would be fairly linear.]

            But that isn’t the case with influenza. There isn’t ONE strain every season. I don’t know if the CDC or anyone else would know how many different influenza strains are active in the US in any given influenza season.

            To quote PAL:
            “Each season, a vaccine is developed by tracking strains emerging in other parts of the world. The vaccine is usually quite effective at preventing flu and complications from flu, but some past seasons have seen new strains emerge after the development of the vaccine.”

            So a strain that is prevalent in each country/state could be a match for the influenza or a complete miss. So the vaccine effectiveness could vary greatly between states or regions within states. The effectiveness of the vaccine is usually overhyped pre-season and the accurate counting of “ILIs” makes it difficult to calculate post season.

          • You seem to imply that the amount of match is essentially random. It is not, and most seasons, the match is very good.

          • Chuck

             /  October 30, 2010

            And in some seasons, the match is very bad. So what criteria do you use to determine a “good” season from a “bad” season and how is your criterion measured?

  5. Excess deaths due to the flu vary considerably from season to season, with best estimates of between about 3000 and 49000 deaths per year.

    You said a mouthful! A best estimate that comes with a +/-1500% qualifier… yeeeeeaaaahhh, “vary considerably” is probably an understatement. 😀

    • that’s not a “range per season” but a min and max since the mid 70s. I could have reported that more accurately.

  6. Karen

     /  October 30, 2010

    My husband’s company has historically offered flu shots to employees. This year they expanded coverage to dependents, too!

    I didn’t take advantage of the company’s offering because I get the flu shot more conveniently from my allergist’s office. But I was really pleased to see it, and I hope my fellow dependents take good advantage of the offer. I wish more large companies would be so proactive.

    I haven’t missed a flu shot since I was (finally) diagnosed with asthma three decades ago, at age 20. I’ve experienced how asthma and a simple cold can interact, complete with ambulance ride to the emergency room; I don’t want to find out how asthma can interact with flu or — deities forbid — pneumonia.

    Flu shots are easy, quick, and relatively painless. My flu shot ached slightly for a day. In contrast, I’ve currently got three tiny, shallow cat scratches that are driving me crazy with their itching, and will for another three or four days. (The perpetrator is currently sitting at my elbow, purring at me.) And people don’t get flu shots because??????

    • Isabel

       /  October 30, 2010

      I guess it depends on convenience. I never get around to it. Scheduling a doctor’s appt. and all. If there was a way I could just walk in, I’d even stand in line to get one. For me the barrier is scheduling that appointment. May not be totally rational, as I hate seeing a doctor for anything.

      • khan

         /  October 31, 2010

        Where I am the grocery store pharmacy gives flu shots. This year they aren’t even requiring appointments, just show up during business hours. Less than 10 minutes.

        • Karen

           /  November 1, 2010

          My local pharmacy is also giving flu shots, without appointments. Just walk in, sign a release form, pay a small fee, and get jabbed.

          I get my flu shot from my allergist’s office because I’m already getting 3 shots of a drug called Xolair and 2 allergy shots. I’m already getting jabbed 5 times, what’s a sixth?

  7. The Gregarious Misanthrope

     /  November 1, 2010

    @Karen

    Very forward thinking to offer shots to dependents. Just because the employee doesn’t get the flu, it doesn’t mean he/she won’t miss work to care for another family member who is sick. The lost productivity can be high. The lost wages for a family can be very high.

    This is an area the vaccine deniers seem very blithe about: the economic costs of disease. This isn’t the 1950’s with mom in her apron and pearls caring for little Johnny and his case of measles. It’s now mom being absent from work for several weeks because Johnny can’t go to school. If you’re already at the edge economically, an event like that can push you over.

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