Flu in 2015: Just the Facts

Right now the infectious disease in the headlines is one that deserves a lot of attention and is always at  the top of my list of infectious disease threats: influenza. 


We are in the beginnings of what will be a rough influenza season. About a week ago, we hit the epidemic threshold when 6.9% of all deaths reported were due to pneumonia and influenza, prompting the CDC to declare an epidemic. In Allegheny County (PA), where I live, there have been 2 deaths reported with close to 2000 cases reported. Pediatric deaths this season number 21 nationally. 

The season is particularly rough because of two factors:

1. The dominant strain is H3N2: Of the several strains of influenza that circulate, H3N2 seasons tend to be more severe likely due to the inherent virulence of the strain with severe cases occurring in the very young and the very old.

2. The vaccine mismatch: Each year viral strains predicted to be dominant are placed in the (now) 4-strain vaccine. This year the H3N2 included is a mismatch and not fully protected against what is the dominant strain. What happened was a new "drifted" variant of H3N2 emerged too late to be included in this year's vaccine.

It's important to note that when you read about numbers of cases confirmed at the county, state, or national level these numbers are only the tip of the iceberg as many physicians don't test formally for influenza because they make the diagnosis clinically and hospitals use tests of varying accuracy (false negatives occur with rapid tests). Chances are if you have symptoms such as fever, muscle aches, and cough you have influenza. Note, influenza doesn't cause gastrointestinal symptoms such as vomiting or diarrhea; it is a pet peeve of mine to see viral gastroenteritis labeled "flu".

What to do?

All is not lost though. There have been rough H3N2 dominated seasons with vaccine mismatch before. There are several things that should be helpful to minimize the impact.

1. Get a vaccination: Though the vaccine is mismatched there will likely be some protection afforded. You may still get the flu, but it could be less severe and less likely to require a visit to the hospital.

2. Low-tech social distancing: If you're sick with the flu, don't go to work; if you're children are sick, keep them out of school. Also, cough into the crook of your elbow not your hands (which you should wash a lot).

A children's nursery rhyme about influenza ("in flew Enza")

A children's nursery rhyme about influenza ("in flew Enza")

3. High risk groups should not try and wait it out. If you're pregnant, immunosuppressed, have underlying health conditions you should not try and wait for the virus to pass. You should see a healthcare provider who may prescribe an antiviral (see #3 below)

3. Doctors should prescribe antivirals: Doctors notoriously under prescribe antivirals for influenza. This is unfortunate as these medications can lessen the severity of influenza symptoms and their duration. There is some concern about shortages, but they are not widespread and people should be able to find drugs like Tamiflu but it may take some looking.

The traditional peak of the flu season is next month, in February, so expect for the season to worsen before it improves.

You can take solace in the fact that next year's vaccine will contain the mismatched strain missing from this year's strain. A larger point to understand about flu vaccines is that because of the genetics of the virus  coupled to our vaccine technology we have to change vaccines frequently and changes can't happen on the fly because of the long lead time to make the vaccine. The scenario occurring this season is something that we will always remain at risk of until a universal flu vaccine--one which doesn't have to be changed seasonally--is developed. That would be something more valuable than the Holy Grail.