Everything you need to know about the flu (influenza) – a very important read for the entire family

What is the influenza virus? What are the different types?

‘The flu’ is an illness that is caused by influenza virus which can be classified into 3 types: A, B and C. Types A and B are the cause of the common flu in humans as well as the cause of epidemics. Each type can be further classified into sub-types, depending on which one of the two glycoproteins is present on the viral envelope, and this dictates the virus’ specific serotype and how aggressive it is.
These glycoproteins are called hemagglutinin (‘H’, of which there are 15 types) and neuraminidase (‘N’, of which there are 9 types).
There is an even further sub-classification to these. But I don’t think we need to go into the details of this, despite the fact that there could be a clinical significance to these different subtypes.
But why am I mentioning all of this in the first place?
The reason is that the Influenza virus type A has a complicated epidemiology that involves mammals and birds that serve as a reservoir for different sub-types, with the potential to infect humans. Since the influenza virus tends to undergo lots of mutations and genetic exchanges between the virus found in animals and the one found in humans, the different H and N antigenic subtypes found in animals all have the potential to infect humans.
Small changes in the virus are called antigenic drifts, while larger changes are referred to as antigenic shifts.
That is why the Influenza virus is a global issue, not only does it cause the well-known seasonal epidemics, but it also has the potential to lead to pandemics (worldwide epidemics). This is something that can happen if a significant antigenic change occurs and a new virus that is unknown to humanity starts circulating.
Indeed, past epidemics have taught us lots about this deadly potential virus.

An example of an influenza pandemic that has occurred in the past

The deadliest influenza pandemic occurred between the years 1918-1920 and was referred to as the “Spanish Flu”.
It is estimated that between 20 to 40 percent of the world’s population were affected and over 20 million people died.
Obviously, poor hygiene levels and the absence of available treatment contributed to the high percentage of morbidity at the time, but this is a classic example of how a new strain of influenza virus was able to hit the world at a high intensity.

What is swine flu?

If you get the hang of the concept behind the existence of different types of influenza virus, you will be able to understand how a new strain of influenza virus appears every year.
Usually, these strains get their names from the animal they originate in.
Influenza A/H1N1, which originated from the exchange of genetic material among the influenza virus in humans, pigs and birds, started circulating in 2009 and was named ‘swine flu’.

Does the specific name of the strain really matter?

Obviously, the specific name does not matter. And it is also obvious to all of us that the virus that causes swine flu does not necessarily lead to a more significant illness than one that wasn’t given such a name.
The concern was (and still is) that a new virus that the human population is not adequately immune to will start circulating and lead to significant mortality.

How does one get infected with the flu?

The virus spreads through droplets. Droplets from a sick person’s breath go through to somebody else’s mucous membranes (mouth, nose or eyes). Coming in contact with surfaces or hands that have contaminated saliva on them is also super infectious.
From experience, I can say that in most of the houses where I have diagnosed someone with influenza there has been more than one sick family member.
This also indicates the high levels of infectivity of this virus.

How is influenza diagnosed?

My answer to this question used to once be that the diagnosis is mostly a clinical one made by the physician:
A patient walks in during the winter, of course, and whatever their age they will have high fever, headache, muscle pain, runny nose and cough – and he could have caught the flu.
Fortunately, nowadays, in the era of rapid antigen tests, we are able to purchase home kits and if one takes the test properly, they can confirm having caught the flu.
Keep in mind that the reliability of many of these tests is not very high, so even when you test negative, you may still have influenza. Please read more of the rapid flu tests in the next link.
In a hospital setting, we can make more accurate diagnoses using PCR testing.

What are the clinical manifestations of the flu?

Getting the real thing leads to a significant and unpleasant illness.
I’m going to repeat this sentence because its important – getting the real virus causes a significant and unpleasant illness.
Why did I emphasize the word “real”? This is because everyone thinks they know whether or not they got the flu this year but in reality, this is far from true.
During winter, lots of people who get a runny nose, with or without fever, are certain they caught the flu.
But usually, when the sickness is mild, it is not caused by the real influenza virus but by one of the other respiratory viruses.
On the other hand, lots of people diagnosed with pneumonia after five days of high fever and cough, and who are sure they had a bacterial pneumonia, will have had influenza without any bacterial complications.
The flu is a severe illness. It includes a fever of 38 degrees Celsius or more, shivering, muscle pain, runny nose, throat ache, cough, headache and shortness of breath. It lasts between 3-7 days. I like to refer to the feeling the flu gives you as “dusted”.

Who is at higher risk for developing severe illness and influenza complications?

The flu manifests as a more severe illness in people who are weaker, such as babies and younger children and in elders with significant underlying medical conditions.
Women who are pregnant, and people who are obese are also at higher risk for severe disease.
Common complications include secondary bacterial infections such as pneumonia, sinusitis, and ear infections. Other complications such as neurologic and cardiac complications are less common.

What is the treatment for influenza?

The treatment is supportive. This means reducing fever, hydration (giving fluids) and relieving pain. Obviously, when there are complications such as secondary bacterial infections then antibiotics are administered, and oxygen is supplied for those who need it.

Is there a medication for the flu?

The CDC recommends antiviral treatment for people who are at higher risk for flu complications who those who have severe illness manifestations.
In practice, there are several flu antiviral medications but the most common one is Oseltamivir (Tamiflu). Its mechanism of action includes the inhibition of neuraminidase, and it is effective against both influenza A and B.
Infectious disease specialists are conflicted with regards to the efficacy of this medication but what is for sure is that for the drug to work it should be started early in the course of the disease. You can read more about Oseltamivir here.
Personally, I wouldn’t trust any of the influenza antivirals to make a significant difference.
Keep in mind that not only is the flu a difficult illness, but because it weakens the body and the immune system, it often leads to secondary bacterial infections.
These infections can be severe and can include pneumonia, sepsis and more.
In younger children we see bacterial ear infections secondary to the flu.
Antibacterial medications do not alter the course of the illness and must be reserved for when there is a real concern for bacterial infections.
Since it is very difficult to distinguish between the flu symptoms and sinusitis, or bacterial pneumonia for example, many people who only have the flu receive antibiotics when they do not actually need them.

Is there a way to prevent the flu?

Yes. There is a vaccine.
Seasonal flu vaccinations are given at the beginning of every winter season. The vaccine strains vary from year to year. The decision for the contents of the vaccine is made by the world health organization depending on the data they gather from the southern hemisphere. But we have a whole chapter about influenza vaccines on this website, you can find it in the link here.

In summary, nobody is sicker than ‘a man who caught the flu’. But seriously now, I have seen so many cases of severe flu, both in children and adults, some of which had no underlying illnesses.
So, keep in mind that the vaccine for the flu is not perfect, but it can provide protection from a very severe illness, and on a personal level I will tell you that I get vaccinated every year and I vaccinate all three of my children every year.

I wish you all good health and good luck!