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Increase in flu cases over the last few weeks nationwide: peak flu season

The link to an interview of me and Sarah from Channel 12 Portland – article and video – on the uptick of influenza cases locally in Portland. Yes – I said it — it’s fist-bumping season!

Regionally and nationally, we are approaching peak flu season. This current surge in caseload has come a little later than the last few years, when it was at around the beginning of February. As a result of this, the clinics and hospitals have seen an increase in caseload as well.

What can be a mild illness in some can be a severe, life-threatening illness in others. The highest risk groups for hospitalization and death are those older than 65 years of age. Persons with underlying health issues, including cardiovascular disease, metabolic disorders (diabetes mellitus), chronic lung conditions and other immunocompromising risks *including advanced age are at the greatest risk of a more serious outcome. It is for these reasons that this population should be encouraged to receive the flu vaccination – even now if one still hasn’t received it. Also crucial is therapy with oseltamivir (or the new agent baloxavir) which can reduce the severity of symptoms, ideally if taken within 48 hours of onset of symptoms.

Nationally, for this influenza season, the CDC estimates that about 20 million have already had influenza-like illness (ILI), there have been about 10 million medical visits regarding ILI, 250,000 flu hospitalization and possibly as many as 20,000 deaths (estimate 16,400-26,700) are attributable to influenza.

It is almost unbelievable the sheer magnitude of those infected, unlike the measles outbreaks we are seeing in the US. This caseload makes a fairly low attributable mortality rate (1/1000) an increasingly important target to try to prevent. Influenza attributable deaths refers to the number of people who have died as a direct consequence of influenza (8-15% are from respiratory failure from influenza pneumonitis) or a result of having the diagnosis of influenza, such as a secondary pneumonia with respiratory failure or cardiac consequence.

Of the caseload nationally, there has been an increase in the amount of H3N2-related influenza. There is nothing characteristic of this virus that makes it more virulent than the most common influenza A virus H1N1. Of the viruses analyzed from a sample thusfar this year, there is much more genetic diversity seen in the H3N2 circulating viruses than the H1N1 (which is largely the same clade). Tests of anti-sera similar to that of the vaccine showed 62% efficacy in neutralizing the H3N2 strains sampled compared to 38% inactive even at high doses. This means that the genetic diversity may be contributing to a decrease in the vaccine’s effectiveness for H3N2.

Why does the flu have a seasonal pattern away from the tropics, which are usually year round in risk? This has always been a question that has stimulated interest and research. There have been multiple factors posited including an increase in transmissability in colder (often drier) weather, changes in mucosal membranes of the nose of respiratory tract that increase the ability for the virus to cause infection, other immune effects of colder temperature, and the increase of indoor cloistering (more people indoor spreading germs). Some studies raise the question as to whether global warming with milder seasons cold increase the likelihood of a sharper curve early into the next flu season.

Infographics | CDC

Take 3 actions to fight the flu infographic
Photo from the CDC website “Take 3” actions to Fight the flu


  1. It is not too late to get the flu vaccination if you haven’t already
  2. Practice prevention habits — including handwashing, social distancing (if you are sick) from others, getting plenty of sleep and eating a well-balanced diet, avoiding smoking or excessive alcohol.
  3. If you do have flu-like symptoms, get seen in the clinic – immediate care or ER (if you are having shortness of breath or any signs of complications and have an underlying risk factor that puts you at risk for more severe disease). You can then be given treatment with oseltamivir and additional care, if needed.
  4. For heaven’s sake, if you have a cough or sneeze, please do it in your sleeve or use a tissue and wash your hands. The visual of coughing and sneezing in the same hand that touches a doorknob or a shakes someone’s hand afterwards is almost unbearable. But I digress..

The CDC has an excellent update of the flu season and tips including “Take 3” actions to fight the flu.

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