Flu

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Mark is sick, he has the flu!

Mark spent his winter holidays with his grandparents, often playing with children from the neighborhood. One day he returned home more tired than usual. He started having a headache and all the muscles of his body ached. He was also having cold chills. When she saw her grandson tremble and his red cheeks, Grandma got worried. She put him to bed, placed the thermometer under his armpit, and hurried to make chamomile tea.

Why precisely chamomile tea?

According to popular belief, chamomile tea helps treat respiratory infections, which is actually true! Chamomile has anti-inflammatory, antimicrobial and calming properties, it boosts immunity and helps our body fight against infections.

At first, Mark protested. He did not want to take his temperature, saying it was nothing, but the thermometer confirmed his grandmother’s suspicions, by showing 39.5 °C! Grandma questioned Mark trying to find out what was hurting him. He was faintly responding that he was feeling pain in his head, legs, arms, throat …and that he was very cold and tired. Then Grandma considered that Mark probably had the flu!

Stars, cold, or a virus?

In many countries, the flu is called influenza. This name comes from the Italian language (influenza del freddo), which means the influence of the cold. In the absence of another explanation, humans have long believed that the occurrence of the disease is affected by heavenly bodies or cold. The Croatian name for the flu comes from the French language and denotes the terms grab or clutch, which describe the sudden onset of the disease.

How do you get the flu?

Flu is a disease caused by a virus, a microbe that is so small that we can't even see it under a light microscope, and it infects the epithelial cells of our respiratory system.

The flu virus has entered Mark's body through his nose or mouth, and perhaps through his hands, which Mark often forgets to wash thoroughly.

Advice: A little school of sneezing and coughing

The next day, the virus reached Mark's lungs where it began to replicate. Already then, Mark could infect someone nearby with the flu virus.

How long are we contagious for the people around us?

Infected people can spread the flu virus two days before the onset of the first symptoms of the disease and up to five days after the symptoms disappear. In children, this period is slightly longer due to the less developed immune system.

Mark’s friend didn’t know that he was contagious and he probably infected Mark with his unwashed hands or by sneezing near him. On the third day after the infection, Mark began to feel the first symptoms of the disease.

What are the symptoms of the flu, how to confirm the flu virus, and what differentiates the flu from the cold?

Battle of annihilation

The virus uses the cells of our body to replicate itself.

Reproduction or replication, what's the difference?

Viruses do not reproduce, they replicate! Reproduction is characteristic for living beings and is the process by which living organisms produce offspring, which consumes a certain amount of energy. Viruses do not have their own energy reserves, so they make their copies by replicating, consuming the energy of the host. The process of replication begins when the virus enters the host cell, and that leads to the formation of numerous new virus particles, the so-called virions that can infect other cells of our body.

Learn more form a video.
Source - author: youtube.com - Israa Ayman

To protect themselves against viruses, cells secrete compounds that have antiviral activity and alert healthy cells that there is an intruder - a virus. As a result of this battle, we feel the symptoms of the disease. When Mark's body realized what was happening, it activated a defense strategy against the virus that must be defeated. The fever was a sign that the battle had begun. About a week after being infected, Mark's body created glycoproteins called antibodies, a key weapon that binds to specific surface parts of the virus. Antibodies can neutralize the virus or bind to the surface of infected cells and cause their destruction. Mark’s specialized immune system cells will participate in virus destruction.

How does our body fight viral infection?

In humans, immunity can be divided according to the period of acquisition into innate and adaptive. Innate immunity is made up of physical obstacles such as the skin, mucousa of the respiratory system and other systems, and various immune cells (e.g. macrophages or leukocytes). Adaptive immunity develops throughout life, usually after getting over some infectious disease or after vaccination. Adaptive immunity is based on the immune response of an organism to an antigen (shown in the figure), whereby lymphocytes, play the main role, i.e. the cooperation of individual immune cells. The immune response is triggered after a microbe, such as a virus, enters our cells and begins to replicate in them. We distinguish between cytotoxic T lymphocytes, which can directly destroy infected cells, and helper T lymphocytes. Helper T lymphocytes recognize foreign antigens presented on the surface of specialized cells of the immune system and initiate the destruction of infected cells with cytotoxic T lymphocytes or activate B lymphocytes. By activating B lymphocytes, they differentiate into plasma cells that produce antibodies specific for a particular type of virus. Besides plasma cells, other types of immune cells called memory T ​​and B lymphocytes are produced because they "remember" the antigens of the virus they previously came in contact with. Memory cells are developed at the first encounter with an antigen, e.g. from a vaccine, and upon re-encountering the same antigen, the change of memory B lymphocytes into the plasma cells that produce antibodies begins. Thanks to this, when our body encounters an antigen, which is known to our immune cells, its response is faster and more effective. Flu virus antibodies bind to hemagglutinin and can neutralize or destroy the virus or bind to the surface of infected cells and cause their destruction.

Flu symptoms are a consequence of our body's defense response. Therefore, fever occurs as a result of the secretion of chemicals that stimulate the immune response. The influence of various chemicals, like certain cytokines, leads to the inflammation that causes many symptoms such as fatigue, pain, redness, etc. A runny nose is caused by the local inflammatory response of the organism to the virus.

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Source - author: youtube.com - Osmosis

Influenza virus glycoproteins? Sounds really flutastic!

When you observe an influenza virus particle under an electron microscope you can see filaments on the surface of a spherical virus. These are surface glycoproteins!

There are two different types of glycoproteins on a particle of the influenza virus: hemagglutinin (HA) and neuraminidase (NA). According to the abbreviations of these glycoproteins, each subtype of influenza virus gets its name or designation. The number next to the letter H represents the type of hemagglutinin and the number next to the letter N the type of neuraminidase. For example, the subtype of the virus that caused the Spanish flu is designated as H1N1.

To date, 18 different types of hemagglutinin and 11 types of neuraminidase have been described. The role of hemagglutinin is to recognize receptors on the host’s cells into which the virus will enter and infect. Neuraminidase is, however, important because it enables replicated viral particles to escape from the cell. The structure of the glycoprotein is written in the genome located within the viral particle. In influenza viruses of types A and B, the genome consists of eight, and in types C and D of seven parts of a single-stranded RNA molecule.


Surface glycoproteins


Two different types of glycoproteins


Types of glycoprotein

When will I be able to play again?

Our Mark was troubled by this question. No matter how bad he was feeling, he just wanted to go back to playing with his friends. His grandmother explained to him that the flu is a disease that we need to take seriously and stay in bed for ten days to avoid complications.

To recover and lower his body temperature as soon as possible, Mark needs to drink plenty of liquids, eat his grandmother's soup and rest a lot.

About fever, rest and warm soup

Fever occurs as a body’s response to infection to inactivate the virus. Although a mild fever is desirable, it is necessary to lower a high fever with medication. It is extremely important to drink enough liquids to prevent dehydration. To avoid exhausting the organism that is weakened by the fight against the virus, it is important to get some rest.

Taking antibiotics to recover?

Influenza, like other viral diseases, cannot be treated with antibiotics. Antibiotics are medications that are used to treat bacterial diseases and have no effect on viruses.

Advice: Take antibiotics only when prescribed by your doctor! The overuse of antibiotics in the world has led to the emergence of bacterial resistance to antibiotics or antibiotic resistance - one of the leading health problems today!

From antiquity to the present

The word virus comes from Latin and means poison because the ancient Romans did not know these microscopic particles existed. The first person who described the flu was the ancient Greek physician Hippocrates, who already in the fifth century BC noted its symptoms. Epidemics and pandemics continued throughout the Middle Ages and the Modern Ages and they continue to this day.

Are there any medications for viral diseases?

Even though antiviral medications do exist, they are rarely used in the treatment of influenza. Most antiviral medications are strictly specific for a particular virus, which limits their action and use in other viral infections. The primary reason for the rare use of antiviral medications is their high cost and the need for a very fast and accurate diagnosis of the disease to start treatment on time.

What should we do when we are sick?

When we get sick, the best thing to do is to follow the doctor's instructions and the traditional advice given by Mark’s Grandma. One flu infection does not provide resistance to re-infection because the virus-causative agent is highly variable and appears in some new variant almost every year. This is why the most effective way to protect yourself from the flu is to get vaccinated regularly!

Tradition and treatment

In the past, pharmacies were not available in every major city as they are today, and medical care was much worse as there were not as many different medicines as today. Therefore, people used medicines available in nature. Most often, these were teas made from various herbs, honey, soups, etc. There is a tradition of treating flu with natural remedies and preparations all over the world. Although people may be distrustful towards some of the traditional advice, often our grandparents' recipes are effective and help in the treatment of flu.

Learn more about all-natural flu and cold remedies at