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Influenza Virus-Pathogen and its Journey into the Human Body

Influenza Virus-Pathogen and its Journey into the Human Body

This report discusses a pathogen and its journey into the human body, with the goal of understanding how it can effectively navigate the human immune system and establish an infection. The chosen pathogen for exploration is the influenza virus. The report will further address key questions pertaining to its entry, interactions with normal flora, evasion of the innate immune system, and strategies to avoid the adaptive immune system.

Point of Entry and Potential Barriers

The flu virus is widely known for its infectious nature; it spreads easily and triggers seasonal respiratory illnesses in humans. The virus typically infects the body by traversing the respiratory tract via inhalation of contaminated droplets. The body’s initial defense against viruses involves confronting them with elaborate physical barriers in the respiratory tract, where minuscule hair-like structures called cilia play a crucial role in capturing and eliminating foreign particles, viruses included (Wille & Holmes, 2020).

By successfully evading our bodily barriers, the influenza virus binds to and enters the respiratory tract cells via surface proteins. Inside the host, the virus replicates rapidly, triggering symptoms including fever, cough, and sore throat. Nonetheless, the body’s defenses are on high alert. The innate immune system deploys white blood cells to the location of infection (Wille & Holmes, 2020). Meanwhile, the adaptive immune system manufactures specific antibodies to combat the flu virus. The virus is neutralized by these antibodies, which also help prevent further infections. The influenza virus is known for being prone to mutate, which allows it to get past these defenses and perhaps lead to recurrent infections (Wille & Holmes, 2020). This is why seasonal flu vaccines are developed to provide protection against the prevalent strains.

Normal Flora and Challenges for Influenza Virus

From various ecological niches within the body, the typical human flora fights off the flu virus. In the upper respiratory tract, there are commensal bacteria like Streptococcus pneumoniae and Haemophilus influenzae, while the lower respiratory tract is home to a variety of species, including Bacteroides, Prevotella, and Firmicutes (Lamoth et al., 2021). In this intricate landscape of hurdles and opponents, the virus seeks to establish a pathway to infection. As part of the respiratory ecosystem, they significantly contribute to maintaining optimal health. To evade the mucosal defenses and mucociliary clearance mechanisms, the virus must first exploit the role of these bacteria. These microbes also stimulate the body’s natural immune system to produce mucus and antimicrobial peptides, which stop the virus from infecting people.

Along the journey, the virus interacts with a number of microorganisms, including strong bacteria like Bacteroides, Prevotella, and Firmicutes (Lamoth et al., 2021). The ability of microbes to not only confer resistant colonies but also regulate immune responses is of great significance. Within this microbial network, the virus faces an obstacle course of resource competition and evasion techniques, including those employed by phagocytic cells vigilantly protecting the lungs. In addition to bacterial challenges, the influenza virus encounters anti-viral defenses such as interferons produced by infected cells, which inhibit viral replication (Lamoth et al., 2021). These defenses are part of the body’s innate immune response, providing a formidable barrier to infection.

Innate Immune System Overview and Pathogen Evasion

As the first line of defense, the innate immune system fights off intruders like the influenza virus. A varied set of rapid and non-specific mechanisms are employed to identify and get rid of unwanted substances (Li et al., 2019). Integral parts of the innate immune system are physical barriers, phagocytic cells, NK cells, complement proteins, and cytokines. By leveraging various defensive measures, the body confronts pathogens, including the influenza virus. Among the first barriers to infection are physical barriers like skin and mucous membranes. As a formidable impediment, these barriers physically block the pathogens’ entry into the body (Li et al., 2019). This mutual aid between mucus and cilia guards against infection by ejecting breathed-in viruses, among them influenza.

White blood cells, such as neutrophils and macrophages, participate in the crucial process by pursuing and eliminating foreign material via the phagocytic route. Phagocytes, which can consume and kill pathogens like influenza virus particles, are essential for immunological defense (Li et al., 2019). Integral to the evasion of host cell detection and destruction is the mechanism of influenza infection, which makes phagocyte elimination challenging. As crucial components of the immune system, NK cells identify and destroy infected cells. These cells can specifically target infected cells containing the influenza virus (Li et al., 2019). The virus has various means to subvert the NK cell’s defense strategy.

Complementary proteins hold the key to robust immunity. Phagocytes rely on specific proteins to help locate and eliminate unwanted guests (Li et al., 2019). The flu virus modifies its surface proteins, thus avoiding the immune system’s recognition and binding mechanisms. Further, when coordinating the immune response to infections, cytokines are essential signaling molecules. Influenza infection sets off a cytokine cascade that brings together diverse immune cells to augment the anti-viral reaction (Li et al., 2019). However, too many cytokines can trigger a detrimental scenario labeled “cytokine storm,” inflicting damage on tissues and intensifying disease severity.

To evade the innate immune system, the influenza virus employs diverse tactics. Through mutations in its surface proteins (hemagglutinin and neuraminidase), the virus adapts and survives, a process referred to as antigenic variation (Li et al., 2019). The rapid transformation of the virus makes it less recognizable by the immune system, hence hindering the adaptive immune system’s ability to respond. Also, the influenza virus interferes with the host’s interferon response, a central anti-viral system, by making proteins that hinder interferon manufacturing or signaling.

Adaptive Immune System Overview and Evasion by Pathogens

In humans, the adaptive immune system functions as a sophisticated defense mechanism, meticulously eliminating pathogens (Montenegro-Landívar et al., 2021). T cells (T lymphocytes) and B cells (B lymphocytes), plus antibodies, form the foundation of the immune system. Central to the adaptive immune system, T cells have a critical function. They are divided into two main types, Cytotoxic T cells (CD8+ T cells) and helper T cells (CD4+ T cells), which serve distinct functions (Montenegro-Landívar et al., 2021). Direct action against infected cells is the domain of cytotoxic T cells, while helper T cells orchestrate the wider immune response by stimulating other immune cells into action. However, B cells play a different role, producing antibodies instead. The Y-shape allows these proteins to interact with specific antigens on pathogens, greatly improving their prospects for elimination. Through the process of affinity maturation, B cells continually improve their antibody production to more effectively combat the intruding pathogen.

Notably, the influenza virus may employ multiple strategies to slow down or evade the adaptive immune system. Rapidly mutating, the virus undergoes changes that render it elusive to antibodies and immune T cells (Montenegro-Landívar et al., 2021). Interference in the activation of T cells and the subsequent impairment of immune cell function is another key way the influenza virus hampers the host’s immune system. Some strains of influenza also can inhibit the presentation of viral antigens to immune cells, hindering the recognition and memory formation by the adaptive immune system (Montenegro-Landívar et al., 2021). These mechanisms collectively make the influenza virus a formidable adversary for the adaptive immune system, necessitating regular vaccine updates to combat evolving strains.


In conclusion, influenza is a highly contagious respiratory virus; various strategies have been developed to navigate the human immune system. Its success in establishing infections relies on its ability to overcome barriers, compete with normal flora, evade the innate immune response through antigenic variation and immune evasion proteins, and hinder the adaptive immune system’s actions. Understanding these interactions is crucial for developing effective preventive and therapeutic strategies against influenza and similar pathogens.


Lamoth, F., Lewis, R. E., Walsh, T. J., & Kontoyiannis, D. P. (2021). Navigating the uncertainties of COVID-19-associated Aspergillosis: a comparison with influenza-associated Aspergillosis. The Journal of Infectious Diseases, 224(10), 1631-1640.

Li, Y. T., Linster, M., Mendenhall, I. H., Su, Y. C., & Smith, G. J. (2019). Avian influenza viruses in humans: lessons from past outbreaks. British Medical Bulletin, 132(1), 81-95.

Montenegro-Landívar, M. F., Tapia-Quirós, P., Vecino, X., Reig, M., Valderrama, C., Granados, M., & Saurina, J. (2021). Polyphenols and their potential role to fight viral diseases: An overview. Science of the Total Environment, 801, 149719.

Wille, M., & Holmes, E. C. (2020). The ecology and evolution of influenza viruses. Cold Spring Harbor perspectives in medicine, 10(7).


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Write a 1,050- to 1,400-word report that answers the following questions:
Choose a point of entry into the human body and outline potential barriers the pathogen might encounter.
Provide an overview of the normal flora in the human body that your pathogen may interact with, and include some challenges the flora might present.

Influenza Virus-Pathogen and its Journey into the Human Body

Influenza Virus-Pathogen and its Journey into the Human Body

Provide an overview of the workings of the innate immune system, including the major components. Are there ways in which your pathogen might slow down or avoid the innate immune system?
Provide an overview of the workings of the adaptive immune system, including the major components. Are there ways in which your pathogen might slow down or avoid the adaptive immune system?
Format your report consistent with APA guidelines.

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