The influenza virus continues to be wildly successful at growing and spreading in people around the world because it slightly changes its structure from time to time to avoid our body’s detection systems. In particular, influenza periodically changes some of the proteins in the outer envelope of the virus to mislead our immune systems. We get fooled again and again.
When someone with the flu coughs or sneezes, huge amounts of virus are spewed out in droplets that travel up to about 6 feet. Inhaling these droplets is the surest way for the virus to enter our bodies. It can also enter through landing on the eye. Beyond this, virus lands on surfaces within range, and we can bring it into our mouth, nose, or eyes with our own hands.
If this year’s influenza virus doesn’t match our immune system’s “wanted” list, it enters our body without setting off the alarm. It attaches to cells that line the respiratory tract and uses their machinery to produce a legion of copies of itself. These spread up and down the respiratory tract and soon we are pumping out huge numbers of viral particles.
Only several days later does our immune system sound the alarm, raise the temperature, and coordinate to expel the invaders. We shed virus for an average of 5 days or so – 1 or 2 of them before we feel sick.
Each year there are an average of 3 million to 5 million severe cases of influenza globally. And 300,000 to 500,000 die from the flu – primarily the very young, the old, and the otherwise unhealthy.
How Bad Will This Year’s Flu Be?
The biggest predictor of how bad the flu will be is how good it’s been at shape-shifting: Is it different from previous years? Does it match our vaccines?
It’s hard to know until the flu actually arrives in town, but the best clue is how it was behaving just before it got here. Australia has their flu season a few months before ours, and their experience is often predictive.
In the last really bad year, the 2009 H1N1 pandemic, they had 59,022 cases in their sparsely populated country by mid-October. This year they’ve had 215,280 cases! And this year’s vaccine (the same one being given now in the US) was only about 10% effective against the predominant strain. Already in the US the number of cases this year is higher than normal.
What Can You Do about Influenza?
Even if the vaccine doesn’t stop you from getting sick this year, it might help your body to recognize the virus sooner and prevent you from getting as sick as you would have otherwise – and from spreading the virus to friends and family.
And I’m a big fan of clean hands before you eat or touch your face, coughing into the elbow, getting plenty of sleep and good food – and giving people who are sick a bit of space. The shape of the flu virus might change often; the shape of good health is often the same.
Chasing Seasonal Influenza. New England Journal of Medicine. 2017.
Low Interim Influenza Vaccine Effectiveness, Australia, 1 May to 24 September 2017. Euro Surveill. 2017.