Category Archives: Structure of Virus
Influenza has two ways to change — one slow and one fast. The slow change is called “drift” — the virus gradually accumulates individual mutations until its surface proteins are no longer recognized by our immune system.
The fast change is called “shift” — different strains of influenza can exchange genetic material if they infect the same cell at the same time. A new “hybrid” strain can emerge with surface proteins that are completely different from the previous year’s epidemic strain.
To picture shift and drift, it helps to know a little bit about influenza virus genetics.
After an epidemic, shouldn’t everyone be immune to the virus? Why is influenza able to come back again and again? The answer lies in the virus’s genetic structure and high mutation rate. The truth of the matter is that an individual’s immune system rarely sees the same influenza virus twice and that means it cannot provide the permanent protection it offers against more stable infectious agents.
Whenever you are infected by a pathogen, your immune system generates compounds called antibodies that bind to the infectious agent and target it for destruction. After the infection is cured, a few of the white blood cells that make those specific antibodies continue to circulate in your blood. Called “memory cells”, these cells are quickly activated