Each winter, anywhere from 10- to 25-per-cent of Canadians suffer a real-life Invasion of the Body Snatchers. Influenza A and B viruses attack victims by "cap-snatching" – the term for stealing a vital molecular tag in human cells – and preventing host cells from expressing their own genes. The viral assault turns normally productive Canadians into feverish zombies haunted by memories of what life was like before the crushing headache, disgusting phlegm and incessant cough took hold. Flu shots are more than 50-per-cent effective against this demonic infection of the respiratory system, depending on how well vaccine makers predicted which flu strains will ravage the masses this year. But until influenza season ends in April, there's no telling who will escape the annual plague. Here is the life cycle of the dreaded flu.
The virus infiltrates your nose and mouth via airborne missiles – a.k.a. infectious droplets coughed or sneezed by sick people – or by sticking to surfaces that you handle before touching your eyes, nose or mouth. You are clueless about the attack.
The virus penetrates cells in your throat and lungs, turning them into factories that replicate the virus and help execute the next stage of the assault. You are infected and contagious, but except for an occasional sniffle, still don't know you're sick.
Flu symptoms strike: fever, shivers, muscle aches, runny nose, sore throat and cough. Prescription antivirals may shorten the illness by days if you take them within 48 hours of the first symptoms, but you don't get to the doctor in time. Over-the-counter remedies are no match for the insidious flu.
Your doctor's advice seems woefully inadequate: drink fluids, rest, eat fruits and vegetables to boost your immune system. Pain relievers lower fever, decongestants reduce stuffiness and expectorants loosen bronchial congestion. But do not work out because it will raise your body temperature, or drink alcohol or coffee, which cause dehydration. You are convinced your misery will never end.
At last, your white knight arrives: your immune system begins to produce the antibodies needed to zap the virus. You start to feel well enough to get back to work or school, but the flu has left its mark. Fatigue persists for days or weeks.
What didn't kill you made you stronger – you are now immune to the virus you just defeated. But it's a small victory. When it comes to the other flu strains out there, you are still a sitting duck.
Sources: Health Canada, Yale Journal of Biology and Medicine, Public Health Agency of Canada, Health Sciences eTraining Foundation and U.S. Centres for Disease Control and Prevention.