The Life Cycle Of Influenza Virus And How Flu Escalates Rapidly

life cycle of influenza virus and how it spreads

Have you ever experienced how a single sneeze turns into a series of successive ones? This sign may not be very apparent to you, but it could be the flu. And the next thing you know, headaches become worse and body pains get more disturbing. Whether it’s the season or your sick workmate, know what makes you catch this illness. After all, when you learn more about the virus life cycle, you also heighten your preventive measures. Sirius Health’s Chatswood medical center offers flu vaccines to combat this. And with the right actions, you could even have lifetime protection. Know more about Influenza today!

What Causes Influenza?

sick in bed with flu

The next time you catch the flu, remember influenza viruses -the culprit to your jeopardized health. Many find it confusing, but the viruses refer to the causative agents and not the illness itself. Like bacteria, viruses are too small to be seen through a naked eye. Indeed, it would have been a lot easier to prevent the flu if you could see it easily. Scientists and researchers use high-caliber equipment types to see these microorganisms. And only if influenza viruses are big enough to see, you will discover that it could morph into multiple shapes. It’s most common form is roughly spherical. However, an influenza virus is not as simple in structure as a plain spherical ball. From inside out, it contains countless proteins that spark chemical reactions inside its mammal or avian host. And like humans, an influenza virus has its own genome. But instead of DNA, an influenza virus has single-stranded RNA.

From the Orthomyxoviridae family of viruses, the influenza virus has further classifications. And depending on the surface protein types and properties, viral subtypes and groups are formed. With the Orthomyxoviridae family notable in causing influenza in mammals and birds, it affects numerous hosts. Hence, transmissions and mutations are common. This spread is the reason for the numerous classifications of the virus. The known types of Influenza virus are:

Influenza A

Affecting a variety of species, including humans and birds, this virus type is potent and widespread. And being the most virulent influenza virus for humans, the A type is the agent behind the biggest pandemics in history. The devastating effects and high death tolls of H1N1 (Spanish and Swine flu) and H5N1 (Avian flu) are only proof of its threat. Much more, this influenza type is prone to mutations. These changes give rise to new forms and maybe the reason for the worldwide outbreak of flu during the Spanish flu pandemic.

Influenza B

Almost exclusive in humans, the only other host for Influenza B virus are the seals. Compared to the influenza A type, Influenza B viruses are less common and more straightforward in form. It only has one subtype and mutates at a lower rate than influenza A. Hence, there is a relatively lower chance of an Influenza B outbreak.

Influenza C

Although influenza C is much less popular, it causes mild illness in children. And with animals and humans as its host, it is capable of causing local epidemics just as Influenza A.

Influenza D

Primarily affecting only cattle and pigs, influenza D type does not affect people. But with structure and properties resembling Influenza C, it is thought to have high potential in infecting humans in the future.

The Life Cycle Of Influenza Virus

Influenza is only one of the many diseases that threaten Americans every year. According to the CDC’s weekly influenza surveillance data, there has been an average of 47 million in-season flu cases from 2019 to 2020. And how a single influenza virus replicates and finds dominion in your body plays the biggest role to its spread. Here is a brief picture on the journey of influenza viruses from the environment to your own cell. 

Step 1: Viral Entry

Before a virus establishes infection and causes symptoms to the host, it has already carried out multiple replications inside a cell. The life cycle of a virus often starts with its entry on the human body. And in the case of influenza, it is through the eyes, nose or mouth. The specific proteins on the viral surface and the receptors on the human cells makes this possible. You will find these cells on the tissue lining that spans the human respiratory tract. When your cell recognizes the foreign protein in the virus, it will initiate binding and attachment.

Step 2: Cell Uptake

The life cycle of influenza virus continues with the internalization of the whole virus by the cell. This cellular phenomenon is also common in science as “endocytosis”. The binding of host receptors and viral proteins caused reactions inside the cell. And this endocytic response to microorganisms is typical and part of the immune process. With the attachment, it will stir structural mechanisms to change in shape and surround the invading pathogen.

Step 3: Fusion

influenza virus inside the body

Cell uptake in the life cycle of flu often ends with the full entry of the virus. A structure called endosome receives the virus and keeps it inside. In normal cases, your cell fuses the endosome with chemicals and substances to kill the microorganism inside. But the influenza virus is smart enough to escape it. It will attach to the endosome membrane and dismantle itself before destruction happens. The viral particles, including its RNA, will flow out of the endosome into the cell’s cytoplasm. The cytoplasm inside the cells refers to the gelatinous liquid filling that keeps parts, like the nucleus, intact. With a high affinity to the cellular nucleus, viral components will attempt an entry. This venture is crucial in establishing the illness and combating your immune response later in the disease process.

Step 4: Viral Replication, Transcription And Translation

Occupying a large area, the nucleus maintains the complex system inside your cell. It stores your DNA that stands as blueprints in creating important cellular structure and components. From the blueprints of your genetic material, the nucleus will replicate and reproduce different protein elements. And wise as ever, the influenza virus will create numerous copies of its own genetic material inside the nucleus. This genetic material also acts as outlines for its own structure. And these multiple genome copies will then incorporate to the normal replication and transcription process of the cell. This joining continues until the cell is ready for the production and manufacturing of proteins.

Step 5: Packaging And Assembly

A chain of reactions occurs to maintain the integrity of the viral protein during the replication process. With the protein products ready, the only thing left for the viruses to do is leave the cell. From the nucleus, viral protein packages are delivered to the outermost shell of the cell. This is when they connect the right viral parts and assemble potent viruses. Thus, numerous viral forms are the signal of its successful life cycle. Few modifications to augment their virulence also happen in this process. With more agents to infect, influenza viruses easily spread inside and out of your body. Patients with flu infect others through the viral release of lungs or airway during a sneeze or cough. 

Survival And Infectivity

Even when its life cycle involves complex conditions, the process happens pretty quickly. It will only take 6 hours for one virus to cast newly created forms from the moment it enters the body. In a water environment with colder temperature, influenza virus even survives for about two to three weeks. On the other hand, the chances of avian influenza virus to spread depends on the waste type of birds and environmental factors. Hence, the transmission of the virus is also possible through direct contact with infected droplets. The infectivity of the influenza virus is highly dependent on many factors, such as ph and temperature. Thus, it could indicate a high chance of successful intervention. Indeed, disinfection with alcohol and hypochlorite could kill the virus in the environment.

Signs And Symptoms Of Influenza Infection

To provide proper treatment for your flu, you need to know how it presents in your system. Here are some of the notable indications to note this disease:

fever as sign of flu
  • Fever or feverish chills
  • Headache
  • Runny or stuffy nose
  • Fatigue and body aches
  • Cough
  • Sore throat

Some people also experience other symptoms, such as nausea and diarrhea. Normally, the host could fight off the virus. And in this case, the infection will only last for approximately seven days. However, with a persistent life cycle and weak response, developing complications are possible. These risks could be anything from a treatable ear infection to life-threatening inflammation of the heart and brain. This only shows how resilient the influenza virus can get. Hence, when difficulty in breathing and seizures happen, it is crucial to seek medical attention immediately.

People With High Risk For Influenza Illness 

While others have a solid host response to the virus, some might find it difficult to fight off. With the capacity to replicate, survive and continue its cycle inside the body, the disease development becomes worse in others. People at high risk include young children, pregnant women, adults more than 65 years of age, cancer patients and people with existing conditions such as AIDS and heart problems.

Treatment And Prevention Of The Flu

Once the influenza virus begins respiratory invasion and its life cycle, it becomes more tricky to beat it. Besides, when the viruses infect the cells, multiple symptoms surface simultaneously. Hence, it is best to protect yourself straightaway before letting it invade your body. After all, as the saying goes, prevention is better than cure. Here are some tips to decrease your chances of getting the avian or seasonal flu:

  • Wash your hands regularly.
  • Avoid crowded areas when influenza cases rise.
  • Get your dose of influenza vaccine.

Protect others as well when you got the flu. This strategy is effective in preventing local spread. By covering your mouth and nose when you sneeze, limiting contact with others and disinfecting things you used and touched, you get to limit its spreading mechanisms.


Although having flu is not an issue for some, people should take it seriously. Viruses are only some of the pathogens that could put many lives at risk and trouble. People and animals are equally susceptible to this disease. And even when development and the life cycle of influenza is relatively difficult to stop, there are many ways for you to prevent it. Opting for vaccinations and hygienic practices will protect not only yourself but others as well. After all, with the perilous complications, anyone should not risk catching the flu.

Leave a Reply

Your email address will not be published. Required fields are marked *