The type A.Let’s zoom in and take

The influenza virus is infamous for causing worldwide flu epidemics each year.

It can mutate, making vaccine development challenging. Learn more here and quiz yourself.

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The Influenza Pandemic of 1918

In 1918, an illness ravaged the world population like never before. People around the globe began getting sick, and it soon became clear that this was not an ordinary illness.

The misery soon spread through the young and old alike, sparing no one in particular. It quickly became a pandemic, and would eventually kill upwards of fifty million people. And the cause? The influenza virus.

Victims of the flu pandemic of 1918
flu pandemic

Today, influenza, typically called the flu, is still going strong. It is one of the trickiest and most versatile of the viruses.

A master of disguise, it is constantly morphing in order to hide from vaccines. Fortunately, modern medicine has made this infectious agent somewhat more manageable. However, influenza still infects up to twenty percent of the U.S. population every year, certainly taking its toll. In this lesson, learn more about the influenza virus and gain an understanding of how it infects people.

The Perplexing Virus

Before we examine influenza, let’s review general virus characteristics. When you get sick, you may say you have a bug. But a virus is a far cry from an actual bug. For starters, viruses are not actually alive.

Although they travel to hosts and spread themselves, they are not living beings. They are parasitic in that they cannot survive on their own, and must rely on the cells of living organisms to reproduce. Viruses seem to exist simply to infect living things and make them sick.If not a living organism, then what exactly is a virus? Simply put, it is a protein shell with genetic information safely tucked inside. It typically hitchhikes in droplets of saliva or mucus, entering through people’s mouths or noses and efficiently infecting their cells. This process will be discussed a little later. Now on to the specifics of influenza.

Types of Influenza

Influenza belongs to the family of viruses known as Orthomyxoviridae. It contains all-important genetic information in the form of single-stranded RNA. Influenza comes in three types, A, B and C. Although humans can be infected by all, it is typically type A that causes widespread illness and epidemics. Influenza A is commonly carried by animals such as birds. Remember the bird flu panic of 2006? This was caused by a strain of Influenza A.

H1N1 virus magnified
Diagram of influenza virus
influenza virus

And how does the flu infect so many new people each year? We mentioned earlier that many viruses travel in droplets, and this is true for influenza. Imagine an infected child that wipes his nose with his hand and then picks up a toy.

The next child that comes along for that toy touches the wet virus-containing mucus and then puts her fingers into her mouth. Almost too easily, the lucky virus has now been provided entrance into a new host, and it quickly gets to work.Once in the body, influenza makes itself at home, settling into the respiratory tract of the host. It binds to host cells using its spiky glycoproteins.

Once bound, the virus releases its RNA into the host cell, hijacking the cell machinery. The unsuspecting cell now has no choice but to replicate the viral RNA. Next, fresh new viruses are assembled and released, hunting down more host cells and repeating this process. At this point, the new host has become sick with the flu.

The Influenza Virus and Vaccines

Possibly the most interesting and challenging aspect of the influenza virus is its ability to mutate. The proteins on the outer shell of viruses are like name tags, identifying them. On many viruses, these proteins never change, allowing vaccines to be developed that will always recognize that particular virus.

However, influenza has the ability to change its proteins in order to hide its identity and evade vaccines.

Flu vaccine
Flu vaccine

This aspect of influenza keeps scientists and doctors very busy. It is their job to study world influenza patterns and predict which strains will most likely circulate for that flu season.

If and when you get your flu shot, you will most likely receive several strains in the hopes that one will be correct.

Lesson Summary

The influenza virus belongs to the family Orthomyxoviridae and is found in types A, B and C. It contains single stranded RNA. Type A influenza is carried by animals and causes epidemics. Influenza travels in droplets to new hosts.

It binds to receptors on the host cells and releases its RNA. The cell replicates the RNA and new viruses are assembled, spreading the sickness. Influenza has the ability to mutate, making it challenging to create a reliable vaccine.


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