Along with colorful leaves, cozy sweaters, pumpkin spice lattes and all the things that make fall great is something predictable yet decidedly less fun: the seasonal flu.
You know that influenza hits in the autumn and that it sucks. But how much do you actually know about the virus itself?
Understanding how the virus infects you — and how the vaccine protects you — will make you better prepared to handle flu season this year.
A note about flu season
Flu usually starts making the news in October, when pharmacies and doctors’ offices start encouraging everyone to get vaccinated. Though flu season usually occurs between autumn and winter, it sometimes lingers into spring.
“Last year we had a very late, very long flu season that peaked in May, which is highly unusual, all across the U.S. The reason for that was because there were two peaks of flu,” says Dr. Helen Chu, an infectious disease specialist at UW Medicine who studies the flu.
Typically, the Seattle area sees flu season hit hardest in January or February, she says.
Flu is (and isn’t) easy to get
Though we tend to think of the flu as a single virus, it actually has four different types: flu A, B, C and D. Flu C is relatively mild and flu D doesn’t infect humans, but flus A and B include the seasonal viruses that ramp up each autumn, plus others (like H1N1, the infamous swine flu).
According to estimates from the Centers for Disease Control and Prevention (CDC), millions — if not tens of millions — of people in the United States get the flu each year. That might make it seem like flu is an extremely contagious virus to have, but that isn’t the case, Chu says.
Virus potency is indicated by scientists using a standard marker called “r nought,” represented by Rø. A virus’s Rø number corresponds to how many people an infected person is likely to spread the disease to.
Flu, perhaps surprisingly, only has an Rø of 1.5 — meaning that one person infected with flu will infect less than two others, on average. In comparison, the virus with the highest potency is measles, which has an Rø of between 12 and 18.