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About Influenza

Pathology

The replication cycle of the influenza virus takes about 4 hours and the rapid onset of influenza symptoms correlate with the peak of viral replication. Death of the host cells from influenza virus infection causes inflammation of the respiratory tract lining – leading to respiratory symtoms (such as nasal discharge, sneezing, non-productive cough and sore throat) – and also induces a rapid immune response.

The common systemic symptoms of influenza (such as fever, headaches and fatigue) are caused by the effects of cytokines (such as interferon-γ, tumor necrosis factor-α) that are produced by immune cells in response to infection with influenza. [1]

More information about the symptoms of influenza can be found here.

Influenza infection and a cytokine storm

Influenza is thought to be one of the conditions able to cause a cytokine storm. Cytokine storms can happen rapidly and cause high mortality. The phrase is used to describe an immune system that has over-reacted and is damaging the body, causing failure of multiple organ systems. The New England Journal of Medicine has published an animated overview of the suggested process. [2]

  1. Eccles R. Understanding the symptoms of the common cold and influenza. Lancet Infect Dis 2005; 5: 718–25.
  2. Osterholm MT. Preparing for the next pandemic. N Engl J Med 2005; 352: 1839–42.
  • "I would describe flu as something that makes you feel very, very ill. You get a headache, aching bones, and are generally fed up"
  • "When I get flu symptoms I feel like a train has run over me"
  • "I felt very sick and, during the first week, I had high temperature. Flu was very different to a cold. I went back to work after two and a half weeks. Then I suffered a setback for another week"
  • "I run a guesthouse; flu would be a real pest for me. I couldn’t cook, I shouldn’t cook, and I wouldn’t cook, so I would need to get a lot of extra help in. It would cost me a lot more money. So flu’s a real problem, a right downturn"
  • "I work on my own and when I can’t work, I have to try not to infect my little children, so they avoid getting the flu as well"
  • "I feel a little numb, like I’m in another dimension. Because in general I have sore throat, headache, I feel all clogged-up. Usually a sensation like I’m floating in the air"
  • "Shivers, sweats, makes you ache. Last time I had flu I was off for two weeks"
  • "I think that I would probably be concerned that I would pass flu onto my children, who might not be able to deal with it as well as I would"
  • "Flu makes you feel like you’ve been hit over the head with a baseball bat. You don’t feel like you can get yourself out of bed as all your energy is drawn from you"
  • "I was incapable of working. It just wasn’t possible at all… and my flu dragged on for more than a week"
  • "I have no strength. It annoys me because I can do nothing, it seems like I’m wasting my time"
  • "Flu’s like being hit by a truck because you feel completely gone. There is no energy left in your body. You are suffering from high temperature. You’re sweating a lot and you feel really unwell"
  • "First of all infinite tiredness, then I feel like sleeping and don’t want to eat"
  • "I felt really miserable because my muscles and my bones were aching. Well, I can hardly describe it, I just felt really awful, absolutely miserable"
  • "It’s like there’s something huge treading on your head, like a deafening noise that destroys the eardrums"
  • "The fever was constantly rising – I immediately measured my temperature as soon as I got home. It was 41°C and it kept rising and I was wondering what’s going on. I was really scared! Everything was hurting and it all happened so fast. Flu came out of the blue"
  • "I always feel like my limbs have iron weights tied to them and I’m going to fall over any minute, a really stuffy runny nose and feel antisocial"
  • "I was totally dependent on others! I was incapable of doing anything at all"
  • "The real flu knocks you for six – you just don’t want to move or do anything. It’s not very nice"
  • "Not being able to go to work. Not being able to do the things I have to do at home and the commitments that I have day by day"