Viral Diseases: Meaning, Types, Causes, Symptoms, Treatment

Viruses are the microorganisms that spread infections. They are made of genetic material, such as DNA or RNA, enclosed in a protein coat called the capsid. These microorganisms enter the body and use the body’s machinery to help them multiply. This process results in the damage and destruction of the host cells. A viral disease is any kind of disease caused by a virus.

This Story also Contains

1. What are Viral Diseases?
2. Viral Diseases in Humans
3. Causes of Viral Diseases
4. How do viruses enter the body?
5. Symptoms of Viral Diseases
6. Diagnostic Tests for Viruses
7. Treatment for Viral Infections
8. How to prevent viral diseases?
9. MCQs on Viral Diseases

Not all viral diseases are contagious; that is, they do not spread from person to person. But some are contagious, such as the flu, common cold, HIV, and herpes. Viral diseases, such as malaria and dengue, spread from the bite of an infected mosquito. Respiratory viruses are spread by droplets through coughing and sneezing. The virus can also spread through contaminated objects, such as doorknobs, tabletops, and personal items. Viral diseases are the topic of the chapter Human Health and Disease. It is a chapter in the biology subject.

What are Viral Diseases?

Viral diseases are infections caused by viruses. Viruses can be called invisible invaders, as they are tiny pathogens that can only replicate inside the living cells of an organism upon invading. The mechanism of action in viruses is unique. The viruses do not possess the cellular organisation required for reproduction, so they cannot replicate outside the living cell like bacteria. So, Viruses need a host cell to use their cellular organisation to become active and reproduce.

Each virus causes a different kind of infection. Several viruses affect humans, i.e., influenza Virus, Rhinovirus, and Human immunodeficiency virus (HIV). The most common type of viral infection is the common cold, which affects the respiratory tract. Other viral diseases are:

• Influenza

• AIDS

• Hepatitis

• Chickenpox

• Polio

• Rabies

• Herpes

• Measles

• Mumps

Typical structure of a bacteriophage and HIV.

Viral Diseases in Humans

There are many viruses that attack humans and lead to disease in humans. Here are a few examples of human viral diseases:

Causes of Viral Diseases

Viruses can be transmitted in various primary ways, contributing to the causes of viral infections. One must understand how viruses spread to implement effective preventive measures.

Airborne transmission occurs by inhaling a virus-containing droplet, released in the air by the infected person. The viral diseases that occur through airborne transmission are influenza and COVID-19. Other ways include direct physical contact with an infected person or surface, exchange of bodily fluids, and contaminated food and water. Vectors like mosquitoes also transmit some viruses.

How do viruses enter the body?

The attachment of the virus to a host cell is the first step in the life cycle of a virus. This step is selective because only cells with the receptors on their surfaces can be infected by a virus. It is like how only keys that fit into existing locks can be used for opening locks.

The surface proteins of the virus bind very strongly to these receptors. Without this step, the virus cannot get inside the cell or begin virus production. This determines which organisms or tissues the virus can infect.

After attachment, the virus enters the host, another stage of the virus's life cycle. The way entry occurs depends on the kind of virus. Some viruses fuse their outer envelope with the host cell membrane, while others are engulfed by the cell through endocytosis.

Others introduce their genetic material through direct injection into the cell. This entry is an important step in the initiation of virus reproduction because it enables the virus to introduce its blueprint of genetic material into the cell to hijack the machinery of the cell.

Symptoms of Viral Diseases

The diseases can result in defects in the human body and are observed through the symptoms exhibited by them. General symptoms caused by viral infections include:

• Flu-like symptoms: sneezing, fever, fatigue, sore throat, and headache.

• Rashes

• Irritability

• Fatigue

• Muscle aches

• Respiratory issues.

Symptoms Specific to the disease and severity depend on the type of infection and duration. Different viruses exhibit unique symptoms, such as:

• Influenza: cough, high fever, and body aches.

• Hepatitis: dark urine, jaundice, and abdominal pain.

• COVID-19: Cough, loss of taste or smell, and breathing issues.

• HIV: fatigue, swollen lymph nodes, and infections.

Mild to severe symptoms can be present, and certain infections may not show any symptoms at all (asymptomatic).

Diagnostic Tests for Viruses

Early detection of viral disease is important for efficient treatment and infection containment. The virus can be diagnosed using a variety of techniques and tests, including:

• Blood tests can detect antibodies or antigens associated with a specific virus.

• With COVID-19 and other viral infections, PCR tests have been a common diagnostic tool. It detects the genetic material of viruses.

• Imaging examines the internal damage in severe cases. For example, lung damage occurs in COVID-19-infected patients.

Treatment for Viral Infections

Symptoms are easy to handle during the early stages. The infections need to be diagnosed at an early stage so they can be treated properly.

• General symptoms such as pain and fever can be relieved with medication, adequate rest, and water.

• Antiviral medications inhibit virus replication within the body

• Serious viral disease cases can be effectively treated with cutting-edge therapies like monoclonal antibodies.

How to prevent viral diseases?

The foremost thing to prevent viral diseases is hygiene practice. Washing your hands regularly, using sanitiser and wearing masks help avoid the spread of viral diseases.

Vaccinations are important against viral infections. Specific vaccinations are available for particular diseases.

To manage viral diseases, it is important to understand their causes, symptoms and preventive measures. Getting medical help as soon as possible is necessary to combat the disease.

Apart from vaccination awareness, maintaining proper hygiene and social distancing are critical components. Virology research must go on to enhance public health and shield the public from viral threats in the future.

MCQs on Viral Diseases

Q1. Common cold is not cured by antibiotics because it is

Option 1: Caused by a Gram-negative bacterium

Option 2: Not an infectious disease

Option 3: Caused by a virus

Option 4: Caused by a Gram-positive bacterium

Correct answer: (3) Caused by a virus

Explanation:

The common cold is caused by a virus named the rhinovirus and Antibiotics are the medications used to treat bacterial diseases. So, antibiotics cannot be used for the treatment of viral diseases. Rhinovirus, the virus responsible for the common cold, cannot be treated with antibiotics, as they are ineffective against viral infections. Instead, viral diseases are managed with rest, hydration, and over-the-counter medications to alleviate symptoms. Misuse of antibiotics for viral infections can contribute to antibiotic resistance, reducing their effectiveness for bacterial infections.

Hence, the correct option is (3) Caused by a virus

Q2. Out of the following which one is a viral disease?

Option 1: Tetanus

Option 2: Measles

Option 3: Cholera

Option 4: Tuberculosis

Correct answer: (2) Measles.

Explanation:

Measles is an infection of a viral aetiology caused by the Rubeola virus and presents with many typical symptoms. Usually, signs first appear within 10 to 14 days following exposure and are dominated by the manifestations of a high fever, dry cough, running nose, and inflamed eyes (conjunctivitis). Koplik's spots, which are small white spots in the mouth, begin to appear after the appearance of symptoms and become visible about 2-3 days afterwards. Usually,y within 3-5 days, there is a red, blotchy rash beginning on the face and spreading over the body.

Hence, the correct answer is Option (2) Measles.

Q3. Assertion: Viral diseases are caused by pathogenic viruses that can infect humans.

Reasoning: Viruses are infectious agents that can replicate within living cells and cause diseases by damaging host tissues.

Option 1: Both Assertion (A) and Reason (R) are the true and Reason (R) is a correct explanation of Assertion (A).

Option 2: Both Assertion (A) and Reason (R) are true but Reason (R) is not a correct explanation of Assertion (A).

Option 3: Assertion (A) is true and Reason (R) is false.

Option 4: Assertion (A) is false and Reason (R) is true.

Correct answer: 2) Both Assertion (A) and Reason (R) are true but Reason (R) is not a correct explanation of Assertion (A).

Explanation:

Viral diseases are caused by pathogenic viruses that can infect humans and cause a range of illnesses. These viruses can be transmitted from person to person, through contact with infected bodily fluids, contaminated surfaces, or contaminated food and water. When a virus enters the body, it can invade host cells and replicate, leading to the development of symptoms.

For example, the human immunodeficiency virus (HIV) is a virus that can cause acquired immunodeficiency syndrome (AIDS), a disease that weakens the immune system and makes individuals more susceptible to other infections. HIV is transmitted through contact with infected bodily fluids, such as blood or semen, and once it enters the body, it can infect and damage immune system cells, leading to a weakened immune system and the development of AIDS.

Therefore, it is important to take appropriate measures to prevent and treat viral diseases, including practising good hygiene, using barrier methods during sexual activity, and seeking appropriate medical care if symptoms develop. Additionally, antiviral medications can be used to treat certain viral infections, but they are not effective against all types of viruses. Vaccines can also be used to prevent certain viral diseases, by stimulating the immune system to produce antibodies against the virus.

Both Assertion (A) and Reason (R) are true but Reason (R) is not a correct explanation of Assertion (A).

Hence, the correct answer is option 2) Both Assertion (A) and Reason (R) are true but Reason (R) is not a correct explanation of Assertion (A).

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