Name: how influenza spreads and replicates
Uploaded: 2026-03-12T13:35:52.000Z
Duration: 1 min 27 s
Channel: JoVE

Influenza is an acute viral disease of the upper respiratory tract.Influenza A is the most prevalent viral strain responsible for infections.H1N1, a subtype of the Influenza A virus, has two surface proteins: hemagglutinin and neuraminidase. These proteins are crucial for its virulence.Hemagglutinin binds to sialic acid receptors on host respiratory epithelial cells, initiating viral attachment.After binding, the virus is internalized into endosomes.The low pH inside the endosome triggers a conformational change in hemagglutinin, causing the viral envelope to merge with the endosomal membrane, releasing viral RNA into the cytoplasm.Next, the viral RNA segments enter the host nucleus and are replicated.Following viral protein synthesis in the cytoplasm, all viral components are transported to the cell membrane for assembly and budding.Neuraminidase activity is required to release the progeny virus from the cell surface by cleaving residual sialic acid.This step completes the viral life cycle and enables the infection of surrounding cells.

influenza

Influenza

Influenza is an acute, highly communicable viral disease that affects the respiratory tract and is responsible for seasonal epidemics worldwide. Influenza A is the most prevalent type associated with widespread outbreaks and is subtyped based on two surface glycoproteins: hemagglutinin (H) and neuraminidase (N), as in H1N1. These glycoproteins are essential for viral infectivity, transmission, and immune recognition. Transmission occurs primarily through respiratory droplets and contaminated surfaces, and high-risk populations are susceptible to severe complications.Viral Entry and Nuclear ImportHemagglutinin mediates viral attachment by binding to sialic acid receptors on respiratory epithelial cells. Following receptor binding, the virus is internalized into an endosome. Acidification within the endosome triggers a conformational change in hemagglutinin, promoting fusion of the viral envelope with the endosomal membrane. This process releases the viral ribonucleoprotein (vRNP) complexes into the cytoplasm. Each vRNP consists of viral RNA wrapped with associated viral proteins, forming a protected functional unit.Influenza is unusual among RNA viruses because replication occurs in the host cell nucleus. Host transport proteins known as importins recognize nuclear localization signals on viral proteins within the vRNP complex. These importins guide the vRNPs through nuclear pore complexes and deliver them into the nucleus, where viral RNA transcription and genome replication occur.Replication, Assembly, and ReleaseNewly synthesized viral mRNA is exported to the cytoplasm for translation. Viral proteins and replicated RNA segments are transported to the plasma membrane, where assembly and budding take place. Neuraminidase cleaves residual sialic acid residues from the host cell surface, facilitating release of progeny virions. This final step enables infection of neighboring cells and contributes to the rapid spread of influenza within the respiratory tract.

Influenza is an acute, highly communicable viral disease that affects the respiratory tract and is responsible for seasonal epidemics worldwide. Influenza ...

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how influenza spreads and replicates

Influenza is a highly contagious viral disease of the respiratory tract. It causes seasonal epidemics around the world. Influenza A is the most common type linked to large outbreaks. It is classified by two surface glycoproteins, hemagglutinin, or H, and neuraminidase, or N, as in H1N1.

These glycoproteins help the virus infect cells, spread between people, and avoid immune detection. Influenza spreads mainly through respiratory droplets and contaminated surfaces. People in high-risk groups can develop severe complications.

Hemagglutinin starts infection by binding to sialic acid receptors on respiratory epithelial cells. The virus then enters an endosome, which is a membrane-bound compartment inside the cell. As the endosome becomes acidic, hemagglutinin changes shape and helps the viral envelope fuse with the endosomal membrane. This releases viral ribonucleoprotein, or vRNP, complexes into the cytoplasm. Each vRNP contains viral RNA and associated viral proteins, which protect and carry the viral genome.

Influenza is unusual among RNA viruses because it replicates in the host cell nucleus. Host transport proteins called importins recognize nuclear localization signals on viral proteins in the vRNP complex. They move the vRNPs through nuclear pore complexes and into the nucleus. There, viral RNA is transcribed and the genome is replicated.

New viral mRNA leaves the nucleus and enters the cytoplasm for translation. Viral proteins and copied RNA segments move to the plasma membrane, where new virus particles assemble and bud. Neuraminidase then cuts remaining sialic acid residues from the host cell surface. This helps newly formed virions leave the cell and infect neighboring cells, which supports the rapid spread of influenza in the respiratory tract.

How Influenza Spreads and Replicates

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Influenza is a highly contagious viral disease of the respiratory tract. It causes seasonal epidemics around the world. Influenza A is the most common type linked to large outbreaks. It is classified by two surface glycoproteins, hemagglutinin, or H, and neuraminidase, or N, as in H1N1. These glycoproteins help the virus infect cells, spread between people, and avoid immune detection. Influenza spreads mainly through respiratory droplets and contaminated surfaces. People in high-risk groups...

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key terms and concepts

Learn how influenza enters respiratory cells, uses the nucleus to replicate, and uses neuraminidase to release new virus particles and spread.

How Influenza Spreads and Replicates | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

microbiology

How Influenza Spreads and Replicates

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