Detailed Guide About How Viruses Affect Us

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Microbes are present everywhere, including in the human body, skin, mucous membranes, and organs. There are four classes of microbes: Viruses, bacteria, fungi, protozoa, and helminths.

Viruses are tiny infectious particles ranging in size from 20nm to 300nm. Scientists estimate that 380 trillion viruses are present outside and inside of the body that can cause minor illnesses and even death depending on the type of virus.

Viruses are also called hijackers because they invade cells, multiply exponentially, and produce copies. They can kill our cells by releasing special types of toxins.

Structure of Viruses: Viruses are of three shapes: Rod-shaped, Helical, and Spherical. They contain either DNA or RNA as genetic material which is wrapped in a protein coat called Capsid.

The capsid is made up of capsomeres that are repeating protein units around the genome or core of the virus.

A virus has an outer covering called an envelope that is derived from the host. An envelope is made of lipoprotein and has special structures called Glycoprotein with spikes embedded in it.

These spikes help the virus in attaching to the host cell. Viruses lack the metabolic machinery required for replication. Due to this, they are also called Obligate Intracellular Parasites. This means that they require a host cell for their replication.

Healthcare workers have to know the different virus types, as is required by the courses they study. If you want to be a nurse, you can also avail dual certifications. The dual nurse practitioner programs online is the best place to get certified in family nursing and adult-gerontology nursing.

Viruses may have a few enzymes such as integrase, reverse transcriptase, and protease.

These enzymes help viruses with replication.

Following are the major factors that help in classification of viruses:

  • Type of genome either DNA or RNA
  • Size and shape
  • Presence or absence of an envelope

Viruses can be human friendly such as defective viruses that interfere with the growth of infectious viruses and decrease the chances of developing an infection.

Sources of Viruses: Viruses are difficult to trace over time because they do not leave any fossils. Molecular techniques based on DNA or RNA are used to study the origin of viruses.

There are three theories that try to explain the origin of viruses:

  1. Reduction or Regressive Hypothesis explains that viruses started as parasites but over time shed their parasitic gene and became dependent on the cells.
  2. Escape or Progressive Hypothesis explains that viruses evolved from the DNA or RNA that escaped from the genes of larger entities.
  3. First Cell Hypothesis suggests viruses originated from a complex of nucleic acid and proteins billions of years ago.

But these are only hypotheses and not an indication of how or why the virus behaves the way that it does.

Transmission of Viruses: Microbes enter our bodies by way of wounds, mouth, body fluids, eyes, nose, and sometimes through sexual contact.

Viruses can spread through:

  • By the touch of an infected patient or virus-carrying objects
  • Some viruses, such as coronavirus, spread through respiratory droplets
  • Viruses such as Human Papillomavirus can spread through direct contact with the infected person
  • Body fluids such as blood and serum can pass viruses from one person to another during blood transfusions
  • Viruses can contaminate food and water. For example, the Noroviruses
  • Viruses such as poliovirus can spread through the fecal-oral route
  • Vectors such as snakes and mosquitoes can spread different types of viruses as well

Viruses are inactive or non-living outside the living cells but can become activated after entering a living body or cell.

Virus in Human Body: When viruses enter our bodies, spikes on their envelope recognize cells for attachment. After attachment, viruses enter inside the cell and uncoating occurs.

The viral genome separates from its capsid. Genome processing occurs in which the viral genome is replicated.

Meanwhile, viral proteins are also formed in host cells by using host cell RNA machinery. When the formation of viral proteins and replication of the genome is completed, new viruses are assembled by combining proteins and the genome.

New viruses are released from the host cell by budding and lysis of the host cell occurs due to a lack of macromolecules and rupturing of the plasma membrane.

In a nutshell, the following are the events of virus replication in the human body:

  • Recognition and attachment to the cell
  • Entry and uncoating in cell
  • Genome and protein processing inside the cell
  • Assembly of viruses
  • Release of viruses

Infected patients and infected cells: Pathogenesis is the development of disease in an individual. In an infected patient, the following events take place:

  1. Transmission of virus in the patient
  2. Replication of virus and damage to cells
  3. Spread of the virus to other parts of the body
  4. Immune response of the body to the virus
  5. Persistence of virus in some cases

The stages a virus goes through in its development in the body are the same as in bacterial infections. The incubation period is the stage during which the patient is unaffected.

The prodromal period in which the patient shows non-specific symptoms.

Specific illness period in which characteristic signs and symptoms occur.  

The recovery period is the stage in which the illness wanes and the patient regains good health.

There are four effects of viral infection on the cell:

(1) Death of the cell

 (2) Fusion of cells to form a multinucleated mass of cells

(3) Malignant formation

(4) No functional or morphological change

Death of the cell mainly occurs when macromolecules synthesis, such as the synthesis of proteins and lipids, is inhibited. Viruses release special materials that can block macromolecule synthesis.

Fighting with Virus: The body’s immune system is the first line of defense against foreign particles, such as viruses. This system can activate and release some cells, known as T-cells, that kill viruses.

T- cells kill viruses by releasing perforins and granzymes. Perforins make holes in viruses and kill them while granzymes degrade viral contents. 

Antiviral drugs and vaccines can also be used to fight viral infections. These drugs damage viral DNA in order to prevent viruses from replicating.

Conclusion: Viruses are micro-organisms need a host to survive and thrive. They can infect the cell if they manage to overcome the body’s natural defenses. They replicate exponentially cause various viral infections.