How The Flu Affects The Body

Scientific studies have allowed experts to discover how the flu affects the body. Most people have suffered from this condition before and know that it is not pleasant. In this article, you will discover where flu-like symptoms occur.
This is how the flu affects the body

Influenza is a viral disease that is also seasonal. Many people have suffered from it before and know how the flu affects the body based on their own experiences. Some bodily mechanisms are activated to protect themselves from the infection and are to blame for the symptoms.

Classic symptoms of the flu are fever, headache, muscle aches and fatigue. When it develops normally without complications, these symptoms disappear on their own without causing lasting problems. However, some cases are more serious.

When the virus attacks people with weakened immune systems, whether due to age or the presence of other underlying diseases, it can even lead to death.

You also need to know that the flu is not the same as a cold. A cold is much milder and the consequences are small and superficial. It is different from how the flu affects the body because the latter is much more aggressive.

The flu virus also has some social effects. Four out of ten people with flu symptoms take time off work while ill and almost all of them reduce the amount of exercise and social activities they participate in.

According to various studies of the symptoms that affect individuals, the most stressful symptom is the feeling of fatigue. Almost half of the people who suffer from the flu state that the drowsy period lasts for a while.

Although fatigue is the most noticeable and troublesome symptom, you will find that it occurs due to fever and muscle aches. This is due to an inflammation of the tissue.

The microscopic process of influenza

The signs and symptoms that manifest themselves externally are expressions of how the flu affects the body on a microscopic level. Different cellular mechanisms explain the occurrence of fever, headache and myalgia.

When the flu virus enters the body, it has about eight hours to spread before the human immune system detects it. The entrance door is the airway and it is located in the epithelial cells of the lungs.

When it penetrates human cells, the virus controls cell organelles that produce proteins and persuades these organelles to function on its behalf. In short, it benefits from the host’s resources to reproduce and survive. The new viral copies thus try to infect other cells.

When the immune system is activated to fight the flu virus, it triggers several reactions. These reactions establish the known flu symptoms and explain how the flu affects the body.

The first cells that are activated are the white blood cells. These cells form the first line for the subsequent activation of inflammatory mediators: cytokines. These are small hormones that carry a message to the immune system. Their task is to cause an activation of organs and tissues to eliminate the virus from the body as quickly as possible.

The immune system
The immune system stops the disease, but also generates flu symptoms.

How the flu affects the body: fever

Of course, we need to talk about fever when it comes to explaining how the flu affects the body. The disease causes fever, which is one of the hallmarks.

Fever occurs when the hypothalamus orders the increase in body temperature. The hypothalamus gives the order because it detects the presence of substances called pyrogens. Among the pyrogens we find the components of bacteria, viruses and cytokines .

As body temperature rises, white blood cells become more efficient. In fact, fever is a defense mechanism, not a consequence of the disease. In addition, microorganisms have problems reproducing at high temperatures.

How the flu affects the body: headaches

It is not entirely clear why the flu causes headaches. However, it is understood that a headache is logical if there is a fever ; This is not just characteristic of the flu.

Cytokines have also been associated with headaches. One type in particular, called interleukin-1, is an inflammatory cytokine just like interferon. Both cytokines and high body temperature lead to vasodilation. The blood vessels in the body are enlarged, and this blood flow can explain the headache with an inherent mechanism similar to migraines.

A man with a fever.
Fever and headache are two classic symptoms of the flu.

How the flu affects the body: muscle pain

Finally, myalgia, or muscle pain, is also characteristic of the flu. Scientific studies have discovered a genetic explanation for this muscle pain in addition to the fact that the effect of cytokines also explains this.

During an infection, the body increases the expression of certain genes that promote the destruction of myocytes. Myocyte cells are muscle tissue cells.

At the same time, inflammatory cytokines cause the muscles to swell to fight the virus. Muscle inflammation is painful and exhausts the muscle since the cells are focused on fighting the virus. This is why those who suffer from the flu experience fatigue.


We probably know about the mechanisms that explain how the flu affects the body, but there is more to investigate. The truth is that you experience fever, headaches and muscle aches when you suffer from this infection.

The symptoms indicate that the immune system is fighting the virus. At the same time , you need to do your part to accelerate the process of proper rest and timely medical consultation.

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