It's not a cold

Well, there’s not one flu. The term is something of a catchall for what you get when you’re infected by one of a variety of influenza virus strains that all tend to cause fevers, coughs, chills, and those other symptoms that have sufferers thinking, “Wait, what if this isn’t just a cold?”

Each year, as the leaves change from green to orange, red, and brown—well, somewhere they do—seasonal flu outbreaks begin in the Unites States. Those fevers, coughs, and chills start to spread throughout the 50 states, and health agencies, starting at the federal level and working down to counties and cities, begin pushing vaccines in the hopes that they’ll stop whichever microbes are causing the headaches and sore throats and such.

Christine Gaiger, San Luis Obispo County’s supervising public health nurse and manager of the communicable disease program, said locals began getting vaccinated at the end of September. This is the first year all local hospitals have adopted mandatory “shot or mask” policies, meaning doctors, nurses, and the like have to get the vaccine or wear a face mask while at work. After receiving a written recommendation from the county’s health officer, the Tenet hospitals enacted the policy as of Oct. 1, Gaiger said, and the Catholic Healthcare West facilities (“even Marian Medical Center!”), which opted out of such a move last year, put it into place as of Nov. 1.

But with literally countless strains floating around the planet, there’s no way a person could get injected with potential protection for all of the bugs that circulate among humans.

So flu vaccine planning is something of a guessing game, though the guesses are educated. Back in July, the U.S. Food and Drug Administration announced the strains its public health experts were expecting to be big this winter, like a must-have Christmas fad—think Tickle Me Elmo or a Cabbage Patch Kid—in reverse.

“You’ve got to quit using the ‘S’ word,” CDC spokesman Jeff Dimond said when asked about the notorious flu that alarmed the planet and gave hypochondriacs so much joy and fear during its 2009 global run. “It’s actually a California sub-strain.”

And that strain is still kicking around, even if it doesn’t kindle the sort of hype it once did. The other expected baddies this season were “A/Perth/16/2009 (H3N2)-like virus” and “B/Brisbane/60/2008-like virus.”

Notice that geographic bit in each of the names? That indicates where the strain was originally isolated. Two of the three strains to watch for this year were first spotted in Australia, and that’s actually pretty common. Dimond said influenza strains tend to move south to north.

In fact, representatives from the CDC, FDA, World Health Organization, and other public health agencies look to the Southern Hemisphere when they’re aiming to predict what the next season’s strains will be in the United States.

Dimond explained that each February, the Advisory Committee on Immunization Practices—made up of doctors and health officials from around the country—meets to crunch numbers and follow gut feelings while looking roughly half a year ahead.

“They don’t just go into a corner and wonder what it’s going to be,” Dimond said. “Nevertheless, they still have to go out on a limb six months ahead of time.

Strains or sub-strains can come from Asia, Africa, or Central America. They’re carried by human travelers, flocks of birds, or whatever. Plus, they mutate, or “reassort.” Swine, for example, can simultaneously catch two different kinds of flu. Swirling around in a perfect pig host, the pair can produce a new strain.

“One of the vexing characteristics of flu is that it is totally unpredictable,” Dimond said. “Flu viruses are always mutating.”

So it’s essentially impossible to project all the various flu migration patterns and combinations, but Dimond said history has shown that health workers can reasonably know what’s coming by looking below the equator.

“It’s important to understand that these are science-based projections,” FDA Press Officer Rita Chappelle wrote to New Times. “However, according to the CDC, even in seasons where the vaccines and strains were not … well matched due to unanticipated changes of the circulating strains, substantial protection has been observed against severe outcomes, presumably because of vaccine-induced cross-reacting antibodies.”