What Are the Main Types and Symptoms of Viral Diseases?
Introduction To Viral Diseases
Viruses are a type of microorganism which are very small infectious agents. DNA or RNA is the piece of genetic material that is enclosed in a protein coat and these lead to the formation of viruses. In the cells of the body, these viruses invade and use those cell's components as they help them to multiply. Infected cells often get destroyed by this process and cause incredibly widespread infection which is called viral disease. Viral diseases are also considered contagious because when the virus enters the human body, it begins to multiply and it spreads from one person to the other. Viral diseases include:
Chickenpox
Influenza
Herpes
AIDS
Human papillomavirus (HPV)
Infectious mononucleosis
Symptoms of Viral Diseases
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Viral disease symptoms vary on the basis of virus type, health history and age of the patient, body area infected, and other factors. Symptoms of viral diseases can include:
Irritability, rash, sneezing.
Swollen lymph nodes and tonsils.
Flu-like symptoms include (headache, fever, cough, sore throat, aches, fatigue, and pains).
Gastrointestinal disturbances like nausea, diarrhea, and vomiting.
Malaise (general ill feeling).
Stuffy and runny nose, postnasal drip, or nasal congestion.
Unexplained weight loss.
Serious Symptoms
In some cases, viral diseases cause serious complications like pneumonia or even life-threatening conditions.
Change in conscious level or alertness.
Green, yellowish or brownish phlegm produced by deep, wet chest cough.
High fever, seizure, chest pain, stiff neck.
Lethargy or unresponsiveness
Shortness of breath, or difficulty in breathing, wheezing.
Jaundice.
Types of Viral Diseases
1. Respiratory Viral Diseases
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These diseases commonly affect either the upper or lower part of the body's respiratory tract. Examples include common cold, influenza, SARS, etc.
Transmission
These Respiratory viruses are either transmitted through droplets generated by sneezing, coughing, or by close contact with contaminated objects.
Treatment
These infections mostly heal on their own. But some medications can be prescribed that help reduce symptoms like cough suppressants, Tamiflu (antiviral drug), Nasal decongestants, and pain relievers.
2. Gastrointestinal Viral Diseases
As the name suggests, these infections affect a human's digestive tract. The viruses that cause the disease are mostly responsible for causing a condition called gastroenteritis, also named as the stomach flu and it is also termed to be contagious.
For Example astrovirus, norovirus, rotavirus infections
Transmission
These diseases are spread due to contamination of water and food with feces or using personal objects and utensils of infectious persons.
Treatment
No treatment is available. It resolves on their own. Meanwhile, the person is advised to take plenty of fluids to make a balance of the loss due to vomiting or diarrhea.
3. Exanthematous Viral Disease
These diseases are caused by Exanthematous viruses that are responsible for causing skin rashes. Most of the viruses of the category are highly contagious.
For Example Rubella, Smallpox, Chickenpox, Measles.
Transmission
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Most of the viruses are transmitted from the droplets generated through sneeze and cough of the infected persons.
Many diseases like chickenpox and smallpox are spread through the contact of fluid present in the broken skin lesions and diseases like chikungunya are spread through the mosquito bite.
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Treatment
It can be cured by managing symptoms. For Chickenpox, antiviral drugs like acyclovir are given to the patients. Some other fever-reducing medications like acetaminophen are also given to other diseases that come under this category.
List of Viral Diseases in Humans
FAQs on Virus Viral Diseases: Complete Guide for Students
1. What is a virus, and how is it different from a bacterium?
A virus is a non-cellular, infectious agent that can only replicate inside the living cells of other organisms. They are considered to be on the boundary of living and non-living. The main difference between a virus and a bacterium is structural: bacteria are single-celled organisms with their own cellular machinery, while viruses are much simpler, consisting only of genetic material (DNA or RNA) enclosed in a protein coat called a capsid. Bacteria can reproduce on their own, whereas viruses must hijack a host cell to multiply.
2. What are some common viral diseases in humans, along with their causative viruses?
Several common diseases are caused by viruses. Here are some key examples as per the CBSE syllabus:
- Common Cold: Caused by Rhinoviruses.
- Influenza (Flu): Caused by Influenza viruses.
- Measles: Caused by the Measles virus (part of the Paramyxovirus family).
- Mumps: Caused by the Mumps virus.
- Chickenpox: Caused by the Varicella-zoster virus.
- Poliomyelitis (Polio): Caused by the Poliovirus.
- Hepatitis B: Caused by the Hepatitis B virus (HBV).
- Acquired Immunodeficiency Syndrome (AIDS): Caused by the Human Immunodeficiency Virus (HIV).
3. What are the common symptoms that indicate a viral infection?
While symptoms vary depending on the specific virus, many viral infections share general signs as the body's immune system responds. These often include: fever, fatigue, body aches (myalgia), headache, and a general feeling of being unwell (malaise). Depending on the affected area, other symptoms can arise, such as a runny nose and sore throat in respiratory infections or a rash in skin infections like measles.
4. Do viruses only infect humans? What are some examples of plant viral diseases?
No, viruses can infect a wide range of organisms, including animals, plants, bacteria, and fungi. Viruses that infect plants can cause significant crop damage. Common symptoms in plants include mosaic patterns on leaves, yellowing, stunted growth, and leaf curl. Some well-known plant viral diseases are:
- Tobacco Mosaic Disease (TMD): Caused by the Tobacco Mosaic Virus (TMV).
- Tomato Spotted Wilt: Caused by the Tomato Spotted Wilt Virus (TSWV).
- Cauliflower Mosaic Disease: Caused by the Cauliflower Mosaic Virus (CaMV).
5. Why are antibiotics ineffective against viral diseases?
Antibiotics are specifically designed to target and destroy bacterial structures and metabolic pathways, such as the cell wall or protein synthesis machinery. Viruses lack these structures. Since viruses are not cells and use the host's cellular machinery to replicate, antibiotics have no mechanism to attack them. Using antibiotics for a viral infection is ineffective and can contribute to antibiotic resistance.
6. How do viruses replicate inside a host cell?
Viruses replicate through a process involving several key stages. The general steps are:
- Attachment: The virus attaches to a specific receptor on the surface of the host cell.
- Penetration: The virus or its genetic material enters the host cell.
- Replication & Synthesis: The virus hijacks the host cell's machinery (like ribosomes and enzymes) to replicate its own genetic material (DNA or RNA) and produce viral proteins.
- Assembly: New viral particles are assembled from the newly made components.
- Release: The new viruses are released from the host cell, often by causing it to burst (lysis), which then go on to infect other cells.
7. What is the basic principle for classifying viruses?
The primary method for classifying viruses is based on the nature of their genetic material and its replication strategy. The Baltimore classification system, for instance, categorises viruses into seven groups. The key criteria include:
- Whether the genetic material is DNA or RNA.
- Whether the nucleic acid is single-stranded (ss) or double-stranded (ds).
- The method used to produce messenger RNA (mRNA) for protein synthesis. For example, a dsDNA virus (like Herpesvirus) is in a different class from a (+)ssRNA virus (like Poliovirus).
8. How do vaccines work to protect us from viral diseases like Polio or Measles?
Vaccines protect against viral diseases by stimulating the body's adaptive immune system without causing the actual illness. They introduce a safe, modified form of the virus (either a weakened, inactivated, or partial virus). This triggers the immune system to produce antibodies and memory cells specific to that virus. If the body later encounters the real, active virus, these memory cells can quickly mount a strong and effective defence, preventing the disease from developing.
