Viral Diseases: Transmission, Symptoms and Prevention

June 5, 2024 1633 0

Viruses are microscopic organisms that contain genetic material encased in a protein coat. They can only replicate inside living cells and are responsible for various diseases. Understanding different viral diseases and their transmission methods is crucial for prevention and treatment.

Understanding Viral Diseases: From Transmission to Prevention

  • Virus Structure and Replication Mechanisms: A virus is a nucleic acid molecule (RNA or DNA) encapsulated in a protein coat or capsid
    • The virus is not a complete cell and can only replicate inside a living cell (bacteria, plants, fungi etc.). 
    • The capsid may have a protective lipid-containing envelope. The capsid and envelope facilitate attachment and penetration into host cells (e.g., via attachment to receptors like ACE 2) and often contain virulence factors
    • Inside the host cell, the nucleic acid molecule utilises cellular proteins and processes for virus replication
    • Based on the type of nucleic acids, viruses can be classified as:
  • DNA Viruses: contain usually double‐stranded DNA (dsDNA) and rarely single‐stranded DNA (ssDNA). These viruses replicate using DNA‐dependent DNA polymerase

    • Example:  Adenovirus
  • RNA Viruses: have typically ssRNA (single-stranded RNA) but may also contain dsRNA
  • Retrovirus: Core contains several copies of reverse transcriptase bound to two identical single-stranded RNA molecules. 
    • Example: Human Immunodeficiency Virus (HIV)
  • The key difference between RNA viruses and retroviruses is that RNA viruses are viruses that have single-stranded or double-stranded RNA as their genetic material, while retroviruses are viruses that have single-stranded RNA as their genetic material but use DNA intermediates in their life cycle.

 

Disease Agent Vector/ Transmission Treatment/Prevention
Dengue Dengue virus

(RNA Virus)

Aedes aegypti or

 Aedes albopictus female mosquitoes

Dengvaxia
Chikungunya

[UPSC 2013]

Chikungunya virus 

(RNA Virus)

Aedes aegypti or

 Aedes albopictus female mosquitoes

Ixchiq 
Poliomyelitis(Polio) Polio virus

(RNA Virus) 

Person to person: faecal-oral route.

Contaminated water/food.

Inactivated poliovirus vaccine (IPV)

Oral poliovirus vaccine (OPV)

AIDS 

[UPSC 2019, 2013]

Human Immunodeficiency Virus (HIV)

[RNA Virus] 

Exchange of body fluids

(excluding saliva)

Anti Retroviral Therapy (ART) with:

Fostemsavir

Ibalizumab-uiyk

Lenacapavir

Lamivudine

Cabotegravir

Zidovudine etc.

Hepatitis- A,

B, C, D, E, G

[UPSC 2019, 2013]

Hepatitis- A,

B, C, D, E, G Viruses

[All are RNA viruses except Hepatitis B- a DNA virus]

Hepatitis A and E- contaminated food or water

Hepatitis B, C, D, G- Parenteral contact with body fluids/blood

HAV Vaccine

HBV Vaccine- also for Hepatitis D

No VaccinesHepatitis C, E, G

Chickenpox

[UPSC 2014]

Varicella-Zoster Virus Air-borne

Direct Contact

Varivax, ProQuad (MMRV)
Ebola Zaire ebolavirus (deadliest strain)

Sudan ebolavirus

Taï Forest ebolavirus

Bundibugyo ebolavirus

All are RNA Viruses

Zoonosis & Body fluids Ervebo

Zabdeno+Mvabea

Nipah Nipah virus (NiV)

[RNA Virus]

Zoonosis, Direct contact and Food contaminated by body fluid of infected animals No approved Vaccines
COVID-19 SARS-CoV-2 (many strains) [RNA Virus] Contact and droplet transmission

Air-borne

Fomite transmission

Covaxin, Covishield, Sputnik-V,  GEMCOVAC-OM (mRNA vaccine)
Japanese encephalitis Japanese encephalitis virus [RNA Virus] Culex tritaeniorhynchus mosquitoes Inactivated Vero cell culture-derived Vaccine (IXIARO)
Zika Fever Zika Virus [RNA Virus] Aedes aegypti or

 Aedes albopictus female mosquitoes

No approved Vaccines
Table: Viral Diseases

 

Prions: Discovered in recent years (Stanley Prusiner, Nobel Prize 1997)– are proteins, which can induce disease [Degenerative central nervous system (CNS) diseases, including spongiform encephalopathy in livestock (mad cow disease and scrapie in sheep) and humans {variant Creutzfeldt–Jakob Disease (vCJD)}].

 

Must Read
Current Affairs Editorial Analysis
Upsc Notes  Upsc Blogs 
NCERT Notes  Free Main Answer Writing

Conclusion 

  • Viruses cause a wide array of diseases ranging from the common cold to more severe conditions like AIDS and Ebola
  • Vaccination, vector control, and proper hygiene practices play pivotal roles in preventing viral infections. 
  • Continued research and public health efforts are essential to combating these viral threats effectively.
Related Articles 
Beyond Single Cell: Viruses, Viroids and Lichens Recombinant Proteins
Rare Disease Day 2024 and Rare Disease in India Classification of Cells: Eukaryotic vs. Prokaryotic and Plant vs. Animal Cells
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Comprehensive coverage with a concise format
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Designed as per recent trends of Prelims questions
हिंदी में भी उपलब्ध

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