Note4Students
From UPSC perspective, the following things are important :
Prelims level: West Nile Virus, Its host, Transmission;
Mains level: NA
Why in the news?
- The Kerala government disclosed the re-emergence of West Nile fever cases in Thrissur, Malappuram, and Kozhikode districts.
- West Nile fever was first detected in Kerala in 2011, with a fatal case recorded in 2019 involving a six-year-old from Malappuram.
What is West Nile Fever?
- West Nile fever is caused by a West Nile Virus (WNV) transmitted through bites from infected Culex mosquitoes.
- The WNV is a mosquito-borne, single-stranded RNA virus.
- According to the WHO, it is a member of the flavi-virus genus and belongs to the Japanese Encephalitis antigenic complex of the family Flaviviridae.
How does it spread?
- It is transmitted by infected mosquitoes between and among humans and animals, including birds, which are the reservoir host of the virus.
- Mosquitoes become infected when they feed on infected birds, which circulate the virus in their blood for a few days.
- The virus eventually gets into the mosquito’s salivary glands.
- During later blood meals (when mosquitoes bite), the virus may be injected into humans and animals, where it can multiply and possibly cause illness.
- WNV can also spread through blood transfusion, from an infected mother to her child, or through exposure to the virus in laboratories.
- It is not known to spread by contact with infected humans or animals.
Symptoms of WNV infection:
- The disease is asymptomatic in 80% of the infected people.
- The rest develop what is called the West Nile fever or severe West Nile disease.
- In these 20% cases, the symptoms include fever, headache, fatigue, body aches, nausea, rash, and swollen glands.
PYQ:[2017] Consider the following statements: 1. In tropical regions, Zika virus disease is transmitted by the same mosquito that transmits dengue. 2. Sexual transmission of Zika virus disease is possible. Which of the statements given above is/are correct? (a) 1 only (b) 2 only (c) Both 1 and 2 (d) Neither 1 nor 2 |
Back2Basics: Type of Viruses
| Subtypes | Description | Examples | |
| DNA Viruses | Herpesviruses | DNA viruses with a complex structure causing various diseases including cold sores, chickenpox, and mononucleosis. | HSV-1, HSV-2, VZV, EBV |
| Papillomaviruses | DNA viruses associated with warts and certain cancers. | HPV | |
| Adenoviruses | DNA viruses causing a wide range of infections in humans. | Adenovirus types causing respiratory, gastrointestinal, and ocular infections | |
| Poxviruses | Large, complex DNA viruses responsible for diseases like smallpox. | Variola virus (smallpox), Vaccinia virus | |
| RNA Viruses | Positive-Sense RNA Viruses | RNA viruses with genomes that can directly serve as mRNA, causing diseases like the common cold, Zika, and COVID-19. | Picornaviruses, Flaviviruses, Coronaviruses |
| Negative-Sense RNA Viruses | RNA viruses requiring transcription into positive-sense RNA before translation, causing diseases like influenza and rabies. | Orthomyxoviruses, Paramyxoviruses, Rhabdoviruses | |
| Retroviruses | RNA viruses that use reverse transcriptase to integrate their genome into the host cell’s DNA. | HIV, HTLV | |
| Double-Stranded RNA (dsRNA) Viruses | RNA viruses with double-stranded RNA genomes causing gastroenteritis and other infections. | Reoviruses | |
| Single-Stranded RNA (ssRNA) Viruses with Ambisense Genome | RNA viruses with genomes containing both positive-sense and negative-sense RNA regions. | Arenaviruses, Bunyaviruses | |
| Single-Stranded RNA (ssRNA) Viruses with Segmented Genome | RNA viruses with genomes consisting of multiple segments, causing diseases like influenza and hemorrhagic fevers. | Orthomyxoviruses, Bunyaviruses | |
| Single-Stranded RNA (ssRNA) Viruses with Circular Genome | Satellite viruses with a circular RNA genome requiring helper viruses for replication. | Hepatitis Delta Virus (HDV) | |
| Enveloped Viruses | Influenza Viruses | RNA viruses surrounded by a lipid envelope causing seasonal flu outbreaks. | Influenza A, B, C viruses |
| Herpesviruses | Enveloped DNA viruses causing diseases like cold sores, chickenpox, and mononucleosis. | HSV-1, HSV-2, VZV, CMV | |
| Coronaviruses | Enveloped RNA viruses causing diseases like severe acute respiratory syndrome (SARS) and COVID-19. | SARS-CoV, MERS-CoV, SARS-CoV-2 | |
| HIV | Enveloped retroviruses responsible for acquired immunodeficiency syndrome (AIDS). | Human immunodeficiency virus | |
| Ebola Virus | Enveloped RNA virus causing severe hemorrhagic fever in humans. | Ebola virus | |
| Non-enveloped Viruses | Adenoviruses | DNA viruses lacking a lipid envelope, causing various infections in humans. | Adenovirus types causing respiratory, gastrointestinal, and ocular infections |
| Papillomaviruses | DNA viruses associated with warts and certain cancers, lacking an envelope. | HPV | |
| Noroviruses | RNA viruses causing gastroenteritis, lacking an envelope. | Norovirus | |
| Rotaviruses | RNA viruses causing severe gastroenteritis in infants and young children, lacking an envelope. | Rotavirus | |
| Bacteriophages | T4 Bacteriophage | Viruses that infect bacteria, with a complex structure and lifecycle. | T4 bacteriophage |
| Lambda Phage | Temperate bacteriophage capable of lysogenic and lytic cycles in E. coli. | Lambda phage |
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