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The Life of the Flu Virus

While strains of flu virus may vary from person to person, the typical flu virus follow a 12-day life cycle in a human body (in the absence of retroviral medications, which can decrease infection time). From the virus entering the body to the immune system attacking and defeating the virus, follow along to learn the life of a flu virus.

  1. Landing in the Body

    • Influenza virus are typically inhaled into the body--which can occur by coming in contact with an infected person or animal. The virus itself looks like a small, spiky oval. The spikes help the virus to land on the surface of cells inside the respiratory tract where the cells overtake and absorb the virus.

    Replication

    • Once the virus is engulfed into the cell, the harmful material contained within the virus is released and works its ways toward the cell nucleus. There, the virus's proteins replicate both viral and messenger RNA, which affects and overtakes the RNA of the entire cell. This produces genes and proteins containing viral properties and is encased first in a protein layer and next in a lipid envelope.

    Spreading

    • These newly formed and encased particles reach the outer membranes of the cell and begin to push their way through. When released, these particles move on to find new cells to invade. When the viruses leave the cell (an occurrence that can take hours), the cell dies.

    Meanwhile

    • The incubation period (meaning the time when a person is contagious) is one to three days for the flu, according to the University of Cape Town. During this time, the virus is replicating and multiplying in the body, causing respiratory symptoms because the normal cells in the lungs are under attack. This can also cause other symptoms, such as fever, muscle aches and extreme fatigue. In those with weaker immune systems (such as babies and the elderly), the influenza virus can lead to serious conditions, such as pneumonia.

    Viral Death

    • The flu virus ultimately dies off. Standard influenza viruses can only survive in the body's systems for a short time. Additionally, each time the virus replicates, RNA proofreading enzymes are not present and therefore the replication process results in errors that lose the ability to replicate or to insert themselves into host cells. Eventually, the virus cells begin to die off, and the person infected starts to feel better.

      In other flu strains, such as avian or swine flu, these strains are more susceptible to mutation and are considered more viable than more standard viral strains. This makes these types of strains significantly more dangerous to the human body.

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