Diseases Caused By Viruses

Viruses are microscopic infectious pathogens that can cause a variety of human diseases. Influenza, measles, HIV/AIDS, COVID-19, and hepatitis are a few examples. These intracellular parasites proliferate within host cells, causing a variety of symptoms and health issues.

Table of Contents:

• What Are Viruses?
• Types And Characteristics Of Diseases Caused By Viruses
• Diagnosis And Transmission Of Diseases Caused By Viruses
• Prevention and Treatment;
• Practice Problems On Diseases Caused By Viruses
• Frequently Asked Questions

What Are Viruses?

The word "viruses" encompasses submicroscopic infectious entities made up of genetic material (DNA or RNA) encased in a protein sheath. They do not have cellular structures and can only replicate within host cells, using the cellular machinery of the host to do so. Viruses cause a wide range of diseases in humans, animals, and plants.

Types And Characteristics Of Diseases Caused By Viruses

Viruses come in a wide variety of shapes and sizes. Here are some of the most common types of viruses and their characteristics:

• DNA Viruses: The genetic substance of these viruses is DNA. Herpesviruses, adenoviruses, and poxviruses are some examples.
• RNA Viruses: The genetic substance of these viruses is RNA. They are further classified as positive-sense RNA viruses (for example, SARS-CoV-2, which produces COVID-19), negative-sense RNA viruses (for example, influenza viruses), and retroviruses (for example, HIV).
• Enveloped Viruses: The outer envelope of these viruses is made of a lipid bilayer produced from the host cell membrane. Influenza viruses and herpes viruses are two examples.
• Non-Enveloped Viruses: Some viruses, such as adenoviruses and noroviruses, do not have an outer envelope.
• Helical Viruses: The genetic material is coiled in a helical pattern in these viruses, which have a helical capsid structure. The tobacco mosaic virus and the Ebola virus are two examples.
• Icosahedral Viruses: Some viruses, such as poliovirus and herpes simplex virus, have a symmetrical icosahedral capsid structure made up of triangular faces.
• Complex Viruses: Viruses possess intricate structures that consist of both helical and icosahedral parts. One instance of such viruses is bacteriophages that attack bacteria.
• Oncogenic Viruses: Certain viruses, such as hepatitis B virus (HBV) and human papillomavirus (HPV), have the ability to induce cancer in the host cells.

Diagnosis And Transmission Of Diseases Caused By Viruses

The diagnosis of diseases caused by viruses involves various methods, including:

• Laboratory testing: Viral diagnostic methods include polymerase chain reaction (PCR), viral culture, antigen detection, and serological assays to detect viral genetic material, antigens, or antibodies in patient samples.
• Clinical evaluation: Doctors examine the patient's medical history and symptoms to determine the possibility of a viral infection.
• Imaging studies: It is possible to determine the severity of an infection or any related problems using imaging techniques like X-rays, computed tomography (CT), or magnetic resonance imaging (MRI).

The transmission of viral diseases can occur through various routes:

• Respiratory droplets: Certain viruses are transmitted through respiratory droplets in the air. For example- In Influenza and COVID-19, an infected person coughs, sneezes or speaks.
• Direct contact: Certain viruses are transmitted through contact with infected body fluids or surfaces. Examples are herpes simplex and hepatitis B.
• Vector transmission: Some viruses, like dengue and Zika, can be transmitted through the bites of mosquitoes or other arthropods that are infected.
• Faecal-oral transmission: The Hepatitis A virus and norovirus are viruses transmitted through contaminated food, water, or improper hygiene habits.
• Sexual transmission: Sexual contact can transmit viruses like human immunodeficiency virus (HIV) and herpes simplex virus type 2 (HSV-2).
• Vertical transmission: An infected mother can pass viruses to her foetus during pregnancy or childbirth. This includes viruses like cytomegalovirus (CMV) and human papillomavirus (HPV).

List of Diseases Caused by Viruses

Prevention and Treatment

The measures of prevention for viral diseases include the following:

• Vaccination: Proper vaccination is recommended to protect against various viral diseases, including measles, influenza, hepatitis, and HPV. Individuals can reduce their risk of contracting these diseases and help prevent their spread in their community by getting vaccinated.
• Good hygiene practices: The hygienic practices that can help reduce the transmission of viruses include frequently washing your hands with soap and water, covering your mouth and nose when coughing/sneezing, and avoiding close contact with infected individuals.
• Vector control: Insect repellents, mosquito nets, and the elimination of breeding areas can help to limit the spread of vector-borne viral infections like dengue and Zika.
• Safe food handling: Foodborne viral illnesses such as norovirus and hepatitis A can be prevented by proper food preparation, cooking, and storage.

The following are the treatment options:

• Antiviral medications: Certain antiviral medications may be prescribed to treat viral infections. These drugs operate by either blocking virus replication or lowering the severity of symptoms. Antiretroviral medications for HIV and antiviral treatments for herpes infections are famous examples.
• Supportive care: Many viral infections are self-limiting, and supportive therapy focuses on symptom relief and management of consequences. This includes drinking water, rest, over-the-counter medicines for pain, and fever reducers.
• Immunoglobulin therapy: In some situations, taking immunoglobulins that contain antibodies targeted against particular viruses can be effective in treating or preventing viral infections.
• Prevention of complications: Monitoring and controlling consequences associated with viral infections, such as subsequent bacterial infections or organ-specific problems, are critical parts of treatment.

Practice Problems On Diseases Caused By Viruses

Q1. What is the name of the virus that causes the common cold?

a. Influenza virus
b. Varicella-zoster virus
c. Rhinovirus
d. Human immunodeficiency virus

Ans: c. Rhinovirus

Rhinovirus, a type of RNA virus, is the main cause of the common cold. On the other hand, the influenza virus is responsible for causing the flu.

Q2. Which of the following conditions is linked to the human papillomavirus (HPV)?

a. Influenza
b. Cervical cancer
c. Hepatitis
d. Measles

Ans: b. Cervical cancer

One of the causes of cervical cancer is specific strains of the human papillomavirus (HPV). It is a sexually transmitted illness that can result in anal, vaginal, and oropharyngeal cancer.

Q3. Which virus is known to cause chickenpox?

a. Varicella-zoster virus
b. Measles virus
c. Hepatitis B virus
d. Herpes simplex virus

Ans: a. Varicella-zoster virus

Varicella-zoster virus, a member of the herpesvirus family, is responsible for causing chickenpox. This viral infection is highly contagious and is characterised by fever and itchy rashes.

Q4. What virus causes acquired immunodeficiency syndrome (AIDS)?

a. Human papillomavirus (HPV)
b. Influenza virus
c. Human immunodeficiency virus (HIV)
d. Hepatitis C virus

Ans: c. Human immunodeficiency virus (HIV)

The human immunodeficiency virus (HIV) causes acquired immunodeficiency syndrome (AIDS). HIV damages the immune system, leaving it vulnerable to infections and specific cancers.

Q5. Which virus is the causative agent for causing measles?

a. Varicella-zoster virus
b. Influenza virus
c. Hepatitis A virus
c. Measles virus

Ans: d. Measles virus

The measles virus is the cause of measles, which is a very contagious RNA virus. The symptoms include fever, cough, rash, and other systemic symptoms.

Frequently Asked Questions

Q1. What are the five diseases caused by viruses?
Answer: The five diseases caused by viruses are:

• COVID-19 (caused by the novel coronavirus, SARS-CoV-2)
• Influenza (flu caused by Influenza viruses, including types A, B, and C)
• Human immunodeficiency virus/acquired immunodeficiency syndrome/HIV/AIDS (caused by HIV retrovirus)
• Measles (caused by Measles virus, a highly contagious RNA virus)
• Hepatitis (caused by hepatitis A, B, C, etc.)

Q2. What are the most common viruses?
Answer: The most common viruses that affect humans include the Herpes simplex virus (HSV), Varicella-zoster virus (chickenpox and shingles), Rhinovirus (common cold), Human papillomavirus (HPV), and Influenza virus (flu).

Q3. What is AIDS?
Answer: Acquired Immunodeficiency Syndrome (AIDS) is a condition resulting from an infection of the human immunodeficiency virus (HIV). HIV harms the immune system, primarily CD4 cells (a kind of white blood cell), impairing the body's ability to fight infections and certain malignancies. If HIV is left untreated, it can progress to AIDS. This condition is characterised by severe immunodeficiency and the increased occurrence of opportunistic diseases and cancers.