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Brace Yourselves for A Bad Flu Season - and Here's Why

by Dr. Bradley van Paridon - February 13 , 2018


Photo Credit: by MC3 Mason Campbell, in the public domain
Photo Credit: by MC3 Mason Campbell, in the public domain

Flu season is upon us in Canada and the US and this year is shaping up to one of the worst in recent memory. Officials in Canada and the US are warning physicians and the public to be prepared as they expect a higher than normal number of cases, hospitalizations, and even deaths.

Influenza, the virus that causes seasonal flu epidemics around the world, is a major concern every year. The World Health Organization reports that flu normally kills between 290 000 to 650 000 worldwide and up to 36 000 in the US alone, yearly—mostly those in groups classified as “high risk populations”, namely, the elderly, young children and people with pre-existing conditions, such as chronic respiratory or immune system conditions. While health officials are warning everyone to be prepared this year, and to of course get vaccinated, it will be these high risk groups that again bear the largest burden from the increased flu activity this year. So why is this year expected to be worse than normal and how do researchers predict this?

Every year flu season occurs during the colder months in the temperate regions of the globe; in tropical regions flu is more or less present year round. Researchers discovered, in 2008, that seasonal flu originates in southeast Asia every year, moves to Australia during their winter (between May and October), then spreads to North America and Europe for our winter (October to May), and finally on to South America. Using this information researchers track and predict which strains are likely to be the most prevalent in each year and design the vaccines accordingly. There are numerous types of influenza virus that infect humans and each year a different combination of strains will make up the seasonal flu epidemic. This why a new flu shot is required each year.

There are three families of the influenza virus—A,B and C—that infect humans. C is not usually a problem for us; B can infect humans but is generally milder, while A is the real problem group and infects birds, pigs and humans. Influenza A has many different strains that are named after the identity of two proteins found on the outside of the virus. Hemagglutinin (HA, or H) and neuraminidase (NA, or N) are two proteins essential to the virus’ ability to infect cells, replicate inside of them and then get back out. There several types of each, 18 for HA and 11 for NA. The mixing of influenza A strains with different variants of HA and NA result in novel combinations and result in the new strains that pop up every year. For example H1N1 is the deadly Spanish flu that caused the largest known pandemic in 1918 and H5N1 is the often talked about avian flu, which, after making a successful jump from birds to humans caused serious disease. It is also one of these influenza A strains, H3N2 specifically, that has caused the increased concern this year.

H3N2 was last seen as the dominant strain in 2014-2015 and resulted in increased flu activity that year as well. This year it was the dominant strain in Australia and is making its way to North America. H3N2 tends to cause more severe symptoms in people, which is on its own enough to cause concern for health care workers. But to make matters worse, this particular strain is also notoriously hard to vaccinate against; in Australia, vaccine efficiency this past flu season was as low as 10%. Influenza A strains acquire subtle mutations throughout their genomes as they move through the population. These mutations make the strains circulating amongst people slightly different than the ones used in the vaccines. On top of this, during the process of growing influenza for use in the vaccine, which is usually done in chicken embryos, the virus mutates as well. Taken together, this makes it very difficult to get an exact match of vaccine strains to the ones actually circulating in people. Since 2004, flu shots have only been around 30% effective against H3N2, while offering efficacies of 61% against H1N1 strains and 54% for influenza B viruses.

This does not, however, mean the vaccine is useless. Vaccination is still the best way to protect yourself, and those around you, from the flu. Aside from vaccination, antiviral drugs are used to treat flu once patients become sick. According to the US Center for Disease Prevention and Control (CDC) all patients, including those not in high risk groups, should know that antivirals are an available treatment option. In a health advisory released in December, the CDC advised patients to speak with their physicians about antivirals if they suspect they have the flu. The sooner treatment begins the more effective it is, and due to the increased concern over flu this year, along with no predicted shortages of antivirals, laboratory confirmation of infection with a flu virus shouldn’t be needed for a prescription.

Another important note about seasonal flu is a basic one: stay home if you are sick. Flu is spread through coughing and sneezing and it is better to stay home and keep those germs to yourself than to stick it out and try to go to work. This is especially true if you work with or around high risk individuals. Also, remember that flu is caused by a virus and antibiotics are not effective, unless you’ve contracted a secondary bacterial infection (which does happen and can be serious). Make sure you consult with your physician as soon as you start to feel ill.

Early reports suggest we are in for bad flu year, but, we won’t know the severity for another few months. This data will be crucial, though, to inform future preventive measures. It appears as though H3N2 is on the rise and researchers will need to especially aware of this when developing vaccines. So far, a universal flu vaccine is not available, so until then, get your flu shot—and if you do get sick, stay home. I hear Netflix has lots of great titles to keep you occupied for a sick day or two.

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Dr. Bradley van Paridon is a writer and science communicator who holds a PhD in Parasitology.


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