Flu Season Is In Full Swing

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Note: This post is part of Mary Carpenter’s “winter series,” updates of her earlier stories on cold-weather well-being.  

THE 2019-2020 FLU season to date is “particularly unusual” because influenza, B which usually circulates toward the end of the flu season, was the first to emerge this year—perhaps due to a vaccine mismatch and general reduced immunity to influenza B, according to Time magazine.

The good news: older adults, who account for most flu deaths each year, are less likely to get influenza B than children and younger adults.  Compared to the 2017-18 flu season, considered the worst of the decade with 61,000 deaths, by early January this year fewer than 5,000 people had died.

At the same time, on the other hand, the CDC reported 32 flu-related pediatric deaths —double compared to that date last year—and the highest number for this time in the flu season for the last 17 years.  Of those, 21 were linked to influenza B and five to the B/Victoria strain for which components were poorly matched in this year’s vaccine.

Compared to a cold, the clearest indicator of flu is symptoms that hit the whole body—chills, fever, aches and respiratory issues—all at once and usually hard. By contrast, most colds start with a runny nose and sneezing that get slowly worse.

“The Big Number” headline in the Washington Post Health Section appearing this fall was “6 to 8 feet”—referring to the average uncovered sneeze sending droplets about six feet; and smaller size particles traveling “closer to eight feet or farther because of a gaslike cloud that keeps them airborne,” according to videos of sneezes from M.I.T.

Other than missing on the B/Victoria strain, this year’s flu shot is well matched to circulating H1N1 and B/Yamagata viruses.  H1N1, which first appeared in March, 2009, is the most rapidly changing of the strains and thus the most worrisome because of its potential for causing a pandemic. H1N1 primarily affects children as does B/Victoria. But the latter may be causing more early infections this year because it has been scarce in recent years, which means diminished immunity in the population.

Peak flu season occurs in either January or February.  This year, the share of doctor visits related to flu dropped slightly during the week ending January 4, as did lab samples testing positive for flu.  On the other hand, flu can last into April and even May—the reason it’s not too late to get the vaccine now.

In the event of a long season, getting the vaccine after late October should offer sufficient protection for six months (through April), while a shot in July or August might not last the season.  (Travelers to the Southern Hemisphere between April and September should check on the need for renewed flu protection.)

In the past, most flu shots were trivalent—protecting against three flu strains, two A and one B.  Starting this year all are quadrivalent with the addition of B/Victoria.  What changes each year are the genetic profiles of each component, with the A (H1N1), for example, getting an update this year from A/Michigan to A/Brisbane—named for the originating location of each component.  In this year’s quadrivalent, the B components are the same as last year, with B/Victoria missing the mark.

The CDC advises everyone to get the same standard-dose vaccination, although recommendations can be different for very young children.  But for older adults, many doctors prefer one of two other options licensed only for those age 65 and over. High-dose Fluzone contains four times the amount of antigen, which provokes a stronger immune response than the standard dose.  The other option, FLUAD, is trivalent plus an adjuvant, which also creates a stronger response. No research has yet compared these two.

While some people blame the flu shot for giving them the flu, the truth is generally one of three possibilities:  side effects from the vaccine can cause mild flu-like symptoms, but not the flu itself, and affect fewer than 1% of people who receive the vaccine; exposure to the flu has occurred before the end of the one-to-two-week period it takes for the vaccine to begin working; or symptoms that sufferers call the flu are actually something different.

True influenza affects only the respiratory system: nose, throat and lungs. What is often called “stomach flu,” on the other hand, can be gastroenteritis—with symptoms of diarrhea, cramps, nausea or vomiting and sometimes fever—lasting from one to 10 days.

Gastroenteritis usually comes from to one of two viruses.  Noroviruses, most likely to spread among people in confined spaces like cruise ships, are often traced to contaminated food or water, although person-to-person infection is possible.  Sickness after eating shellfish, dubbed “winter vomiting virus,” most often comes from norovirus, although the cause can also be bacterial—usually E.coli.

The other, rotoviruses, are most common and most severe in young children who put their fingers or other contaminated objects into their mouths, and spreads easily in institutional settings.  Adults, who often have no symptoms, can unknowingly spread the virus.

Advice for those wishing to emerge unscathed from flu season, besides getting the shot, includes washing hands and avoiding people who might be sick. But because the incubation period for flu can last as long as four days, it’s hard to know when someone close to you might already be spreading it.  Staying at home is therefore the most common recommendation—but one that’s impossible for almost everyone to follow.

Mary Carpenter

Every Tuesday, count on well-being editor Mary Carpenter to deliver health news you can use.