1. Entry: The flu virus enters our bodies through the nose, mouth, or eyes. It prefers to target cells lining our respiratory tract, such as those in the nose, throat, and lungs.
2. Attachment: Once inside, the flu virus uses special proteins on its surface, called hemagglutinin (HA), to attach to specific receptors on the surface of our cells. These receptors are like docking stations that allow the virus to gain a foothold.
3. Fusion: After attachment, the virus undergoes a structural change, allowing another viral protein called neuraminidase (NA) to fuse the viral envelope with the cell membrane. This fusion creates a pathway for the viral genome to enter the cell.
4. Genome Replication: Inside the cell, the viral RNA genome is released and transported to the nucleus, the control center of the cell. Here, the viral RNA hijacks the cell's machinery to produce multiple copies of its genetic material.
5. Protein Synthesis: The viral RNA also directs the cell to produce viral proteins, including HA, NA, and other components that will form new virus particles.
6. Assembly: The newly synthesized viral proteins are transported back to the cell membrane. HA and NA proteins are embedded into the cell's outer layer, while other viral proteins form the core of a new virus particle.
7. Budding: The newly formed virus particles bud out from the cell's surface, taking a piece of the cell membrane with them. This process is aided by the NA protein, which helps the virus escape from the cell without destroying it.
8. Release and Spread: The released virus particles are free to infect neighboring cells, repeating the cycle of infection and spreading the virus throughout the respiratory tract.
This continuous cycle of infection leads to the symptoms we associate with the flu, such as fever, cough, sore throat, runny nose, muscle aches, and fatigue. The flu virus's ability to rapidly replicate and evade our immune system makes it highly contagious, capable of causing widespread outbreaks during flu season.
