Health

How This Flu Season Could Have A Second Wave

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Here’s a sign at a Walgreens pharmacy in San Francisco, California. (Photo by Justin Sullivan/Getty Images)

Bad movies can have sequels with the sequels often being bad. Ghost Rider featured a man with a flaming skeleton head riding a motorcycle. Ghost Rider 2&nbsp;featured a man with a flaming skeleton head riding a motorcycle. It didn’t get better the second time around.

How about bad flu seasons like this year’s? The number of people with the flu seemed to peak about 3 months ago with this number declining since then. But will there be a&nbsp;sequel, a second wave, this Spring? And if so how bad will the sequel be?

Whenever two different strains of flu widely circulate and peak at different times during a given flu season, you worry about two waves of the flu occurring. That’s because having been infected with one strain of the flu doesn’t necessarily give you immunity to another strain, unless the two strains are very similar. When it comes to the flu, your immune system&nbsp;can be like a very focused defense system, like a defensive coach who says, “OK, we’ve played against Tom Brady and the New England Patriots. It didn’t go well, resulting in fever, chills, body aches, a runny nose, and feeling like garbage. But we will be ready next time he and the Patriots come to town. Our defense will be a Brady-stopper.” However, if some other team comes along, say the Seattle Seahawks, that focused defense won’t be ready.

That’s sort of the situation this flu season. There are now two influenza strains that have been circulating widely. A particularly nasty&nbsp;influenza A virus strain named H3N2 largely powered the first wave of this 2017-2018 flu season. But now a B-lister, as in an influenza B strain of the Yamagata lineage, seems to be causing more of the ruckus. Here are some recent numbers from FluView, the Weekly U.S. Influenza Surveillance Report from the Centers for Disease Control and Prevention (CDC):

Week 13 Data Cumulative since
October 1, 2017 (Week 40)
No. of specimens tested 21,823 1,073,126
No. of positive specimens (%) 3,357 (15.4%) 211,428 (19.7%)
Positive specimens by type
&nbsp;&nbsp;&nbsp;&nbsp;Influenza A 1,329 (39.6%) 147,096 (69.6%)
&nbsp;&nbsp;&nbsp;&nbsp;Influenza B 2,028 (60.4%) 64,332 (30.4%)

These numbers are based on respiratory specimens collected from a set of public health and clinical laboratories located across the country and Puerto Rico. Note that these numbers represent just a sample of the labs in the U.S. and Puerto Rico and just a fraction of all the people who have developed flu-like symptoms. If you had flu-like symptoms but didn’t go to a doctor’s office or hospital that happened to be connected with one of these labs and didn’t leave your sputum there to get tested, then your case did not count.

But these numbers do give us a rough idea of which viral strains have been active and continue to be active. As you can see from the numbers above, for the flu season so far, influenza A was responsible for close to 70% of all the specimens that tested positive for flu. However, for Week 13 of this year or the last week of March, influenza B appeared in 60% of the specimens.

What will determine if a second wave of the flu season occurs this Spring is the timing of influenza B activity and whether it spreads widely this Spring. FluView data suggests that influenza A activity peaked back in January and has been on the downswing since then. So far, influenza B activity seemed to reach its highest activity in February (7785 specimens testing positive for influenza&nbsp;B in Week 7 of this year). But while the numbers from Weeks 12 and 13 are comparatively lower (2690 and 2028 respectively), influenza B does not seem to be clearly on the decline just yet. While the numbers currently aren’t saying that a second wave driven by Influenza B will occur, you can’t quite wave goodbye to the the possibility of a second wave.

If you think you have the flu, don’t go to work or school (Photo: Shutterstock)

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Here’s a sign at a Walgreens pharmacy in San Francisco, California. (Photo by Justin Sullivan/Getty Images)

Bad movies can have sequels with the sequels often being bad. Ghost Rider featured a man with a flaming skeleton head riding a motorcycle. Ghost Rider 2 featured a man with a flaming skeleton head riding a motorcycle. It didn’t get better the second time around.

How about bad flu seasons like this year’s? The number of people with the flu seemed to peak about 3 months ago with this number declining since then. But will there be a sequel, a second wave, this Spring? And if so how bad will the sequel be?

Whenever two different strains of flu widely circulate and peak at different times during a given flu season, you worry about two waves of the flu occurring. That’s because having been infected with one strain of the flu doesn’t necessarily give you immunity to another strain, unless the two strains are very similar. When it comes to the flu, your immune system can be like a very focused defense system, like a defensive coach who says, “OK, we’ve played against Tom Brady and the New England Patriots. It didn’t go well, resulting in fever, chills, body aches, a runny nose, and feeling like garbage. But we will be ready next time he and the Patriots come to town. Our defense will be a Brady-stopper.” However, if some other team comes along, say the Seattle Seahawks, that focused defense won’t be ready.

That’s sort of the situation this flu season. There are now two influenza strains that have been circulating widely. A particularly nasty influenza A virus strain named H3N2 largely powered the first wave of this 2017-2018 flu season. But now a B-lister, as in an influenza B strain of the Yamagata lineage, seems to be causing more of the ruckus. Here are some recent numbers from FluView, the Weekly U.S. Influenza Surveillance Report from the Centers for Disease Control and Prevention (CDC):

Week 13 Data Cumulative since
October 1, 2017 (Week 40)
No. of specimens tested 21,823 1,073,126
No. of positive specimens (%) 3,357 (15.4%) 211,428 (19.7%)
Positive specimens by type
    Influenza A 1,329 (39.6%) 147,096 (69.6%)
    Influenza B 2,028 (60.4%) 64,332 (30.4%)

These numbers are based on respiratory specimens collected from a set of public health and clinical laboratories located across the country and Puerto Rico. Note that these numbers represent just a sample of the labs in the U.S. and Puerto Rico and just a fraction of all the people who have developed flu-like symptoms. If you had flu-like symptoms but didn’t go to a doctor’s office or hospital that happened to be connected with one of these labs and didn’t leave your sputum there to get tested, then your case did not count.

But these numbers do give us a rough idea of which viral strains have been active and continue to be active. As you can see from the numbers above, for the flu season so far, influenza A was responsible for close to 70% of all the specimens that tested positive for flu. However, for Week 13 of this year or the last week of March, influenza B appeared in 60% of the specimens.

What will determine if a second wave of the flu season occurs this Spring is the timing of influenza B activity and whether it spreads widely this Spring. FluView data suggests that influenza A activity peaked back in January and has been on the downswing since then. So far, influenza B activity seemed to reach its highest activity in February (7785 specimens testing positive for influenza B in Week 7 of this year). But while the numbers from Weeks 12 and 13 are comparatively lower (2690 and 2028 respectively), influenza B does not seem to be clearly on the decline just yet. While the numbers currently aren’t saying that a second wave driven by Influenza B will occur, you can’t quite wave goodbye to the the possibility of a second wave.

If you think you have the flu, don’t go to work or school (Photo: Shutterstock)

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