CURRENT AFFAIRS | MARCH 2026
CLAT Relevance
• RNA vs DNA viruses — mutation rates and pandemic potential
• Nipah virus: 18kb negative-sense single-stranded RNA
• Baltimore Classification of viruses
• WHO Disease X concept and global health preparedness
• RNA vs DNA viruses — mutation rates and pandemic potential
• Nipah virus: 18kb negative-sense single-stranded RNA
• Baltimore Classification of viruses
• WHO Disease X concept and global health preparedness
DNA vs RNA Viruses — The Key Difference
Key Distinction
• DNA viruses: Use DNA polymerase with proofreading ability — fewer mutations, more stable
• RNA viruses: Use RNA-dependent RNA polymerase (RdRp) with NO proofreading — high mutation rate
• RNA viruses mutate 100-1000x faster than DNA viruses
• DNA viruses: Use DNA polymerase with proofreading ability — fewer mutations, more stable
• RNA viruses: Use RNA-dependent RNA polymerase (RdRp) with NO proofreading — high mutation rate
• RNA viruses mutate 100-1000x faster than DNA viruses
Examples
- DNA viruses: Smallpox (Variola), Hepatitis B, Herpes, HPV
- RNA viruses: Nipah, Influenza, SARS-CoV-2, Ebola, Dengue, HIV, Rabies, Zika
- Most pandemic-causing pathogens have been RNA viruses
Nipah Virus — Genomic Profile
- Genome type: Negative-sense single-stranded RNA
- Genome size: ~18 kilobases (kb)
- Family: Paramyxoviridae, Genus: Henipavirus
- Negative-sense means the RNA must be converted to positive-sense by viral RNA polymerase before protein translation
CLAT Angle — Science
Positive-sense RNA = can directly act as mRNA for protein synthesis
Negative-sense RNA = must first be transcribed into complementary positive-sense strand
This distinction matters for how quickly a virus can replicate inside host cells.
Positive-sense RNA = can directly act as mRNA for protein synthesis
Negative-sense RNA = must first be transcribed into complementary positive-sense strand
This distinction matters for how quickly a virus can replicate inside host cells.
Why RNA Viruses Are Dangerous
- High mutation rate — enables rapid evolution of new variants
- Antigenic drift — gradual mutations in surface proteins help virus evade immunity
- Antigenic shift — sudden major changes through genome reassortment (e.g., influenza)
- Drug resistance — mutations can make antiviral drugs ineffective
- Vaccine escape — new variants may partially evade existing vaccines
- Zoonotic potential — high mutation rate facilitates cross-species transmission
Baltimore Classification
Baltimore Classification System
Developed by David Baltimore (Nobel laureate). Classifies viruses into 7 groups based on genome type and replication strategy:
• Group I: dsDNA (e.g., Herpes)
• Group II: ssDNA (e.g., Parvovirus)
• Group III: dsRNA (e.g., Rotavirus)
• Group IV: (+)ssRNA (e.g., SARS-CoV-2, Dengue)
• Group V: (-)ssRNA (e.g., Nipah, Ebola, Influenza)
• Group VI: ssRNA-RT (e.g., HIV)
• Group VII: dsDNA-RT (e.g., Hepatitis B)
Developed by David Baltimore (Nobel laureate). Classifies viruses into 7 groups based on genome type and replication strategy:
• Group I: dsDNA (e.g., Herpes)
• Group II: ssDNA (e.g., Parvovirus)
• Group III: dsRNA (e.g., Rotavirus)
• Group IV: (+)ssRNA (e.g., SARS-CoV-2, Dengue)
• Group V: (-)ssRNA (e.g., Nipah, Ebola, Influenza)
• Group VI: ssRNA-RT (e.g., HIV)
• Group VII: dsDNA-RT (e.g., Hepatitis B)
WHO Disease X — Preparedness for the Unknown
- Disease X = WHO concept representing an unknown future pathogen with pandemic potential
- Added to WHO’s R&D Blueprint list of priority diseases
- Most likely candidate: a novel RNA virus from zoonotic source
- Demands: platform technologies (mRNA vaccines, broad-spectrum antivirals), surveillance, rapid response
Global Health Security Implications
- IHR (International Health Regulations) 2005 — binding WHO framework for disease reporting
- Pandemic Treaty — under negotiation at WHO (as of 2026)
- CEPI (Coalition for Epidemic Preparedness Innovations) — funds vaccine development for priority pathogens
- India’s role: “Pharmacy of the World” — critical for vaccine manufacturing capacity
Key Terms for CLAT
- RNA polymerase — Enzyme that copies RNA; lacks proofreading in viruses
- Antigenic drift/shift — Mechanisms of viral evolution
- Baltimore Classification — Virus classification by genome type
- Disease X — WHO concept for unknown future pandemic pathogen
- Negative-sense RNA — RNA that cannot directly serve as mRNA
Source: UPSC Essentials, The Indian Express — March 2026
Practice Quiz
Test your understanding with these 10 MCQs:
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