Influenza or the flu is a viral infection that infects the nose, throat or lungs. The influenza virus is extremely small yet can be fatal. It has caused pandemics in the past and it still torments humans and even some animals such as pigs and birds. It is important to learn about them to avoid future pandemics and even manage them if it happens.


There are 4 main types of influenza: A, B, C and D. Only A and B affect humans. Furthermore, A is the only type that causes pandemics hence, will be the focus of this article.

The structure of the Influenza virus

It is made of viral genetic material(nucleoprotein) which is enclosed in a protein shell that protects these viral genes during transmission. The protein shell is further protected by an envelope; this envelope not only protects the virus but aids it to attach to the cell membranes of its host and infect it. Outside of this envelope are spikes. The flu virus has 2 protein spikes: An H spike that serves as the key to enter the host cells and an N spike that allows the virus to break away from one cell and infect other cells.

The protein spikes are used in classifying the different influenza viruses. There are about 18 H spikes and 11 N spikes. For example, HINI means that the virus is made up of an H1 spike, and an N1 spike which affects humans whilst H5N1 means the virus has an H5 Spike combined with an N1 spike which affects poultry and humans. The H stands for Hemagluttinin and the N stands for Neuraminidase.

Human influenza subtypes

In humans, only three subtypes of H(H1, H2, H3) and two subtypes of N(N1, N2) can infect humans.

In 1918-1919, there was an influenza pandemic that infected 1/3rd of the world H5N1. In the 2009 pandemic, the swine flu, Influenza A(H1N1) infected humans.

The viruses undergo antigenic drift where they change(mutate) their H and N surfaces(antigens) to create more deadly ones. These types are the ones that cause pandemics and are difficult to manage.

Other subtypes

In 1997, the avian flu or bird flu with type H5N1 was observed. This affected poultry however it was able to infect humans who ate poultry products that had been infected. This could have been avoided if they thoroughly cooked it. This type cannot spread from humans to humans but through ingestion of infected poultry products.


The viruses spread when an infected person coughs or sneezes. The viruses are tiny and form aerosols. The droplets can also spread when a person touches a surface with these droplets. The individual then touches the face with it and the virus may somehow find its way through the nose, mouth or eyes. As the droplets from the infected person fall on you, they might attach to your nose and travel to the throat, nose and lungs as a person breathes in.

In the throat, the H spike of the virus attaches to receptors on your body cells. The receptors serve as doors into the cell. Only the right key will unlock the door. Thus, there are different H spikes and depending on the type, they will attach to the door and unlock it. When this happens, the virus can enter your cell. The cell membrane protects the content of your cell. As the virus enters, the viral envelope attaches to the cell membrane of your cell. However, when this happens, your cell loses its security.

The virus then opens its shell to release its viral genetic material. The viral genetic material manipulates your cell’s genes to produce products of the virus using ribosomes and other organelles present. At this state, your cell loses the fight. The virus becomes a dictator and uses your cell’s own resources(genes) to make more of itself. New viral products such as the H and N spikes, the genetic material and the others gather at the outside of the infected cell. The products come together to form a new virus. The N spike helps the virus to detach from the cell membrane and move on to a different cell to infect it.


Use of neuraminidase inhibitors: The drugs given to an individual will help stop the spread of infection. If a virus infects a cell in your body, the best chance to fight the infection is to stop the virus from infecting other cells. As for the infected cell, it is already damaged and your immune system will clear them so that new uninfected cells can replace them. One way to stop the spread is to prevent the N spike on the virus from detaching the virus and infecting other healthy cells. Most drugs use this mechanism so that the virus will stay only on the infected cell to allow the immune system enough time to clear them.

Use of antibiotics- the use of antibiotics prevents any opportunistic bacteria from infecting your cells as your body is busy fighting the virus.

Isolation-infected individuals are highly contagious. Isolation from healthy individuals especially the young whose immune systems are now forming and the elderly who have weakened immune systems will reduce mortality.

Another way to avoid influenza viruses is the use of vaccines. Vaccines are weakened forms of the virus that will not cause disease. As the vaccine is introduced into your body, your immune system will take approximately 2 weeks to produce antibodies against the virus. This is such that when the real thing comes into your body, antibodies will attach to them and prevent them from entering your cell. Antibodies can clump many of these viruses and other cells of your immune system can engulf(swallow) them thereby preventing infection.


The virus can cause various symptoms such as runny nose, sore throats, fever and others that will last for a while. However, the virus can also lead to some serious complications. As the virus infects the cells, it overwhelms the immune system and weakens it. This allows other bacteria to get into the lungs and cause harm. Some of these may lead to severe secondary pneumonia. This makes breathing difficult and may result in death. In the past, this has been the major cause of death because the lung is responsible for distributing oxygen.

If oxygen distribution becomes low, the organs of the body begin to starve and may lead to organ shut down. Due to advanced technology, a ventilator may be used to support this function to support the organs from starving. However, if this happens in people with underlying medical conditions, their conditions may worsen and the body may just give up.


  1. Center for Disease Control and Prevention. Influenza. Retrieved from
  2. Microbiology and Molecular Genetics. Retrieved from


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