RNA viruses are genetic pathogens that replicate using RNA, leading to diseases such as Ebola, Oncogenic Viruses. Known for high mutation rates, they demand vigilant surveillance, vaccination, and clinical care—essential in nursing and virology.
Introduction
RNA viruses constitute a vast and diverse group of pathogens responsible for significant morbidity and mortality worldwide. Characterised by their ribonucleic acid (RNA) genome, these viruses display high mutation rates, rapid evolution, and efficient adaptability, contributing to their clinical relevance in human disease. RNA virus infections span a broad spectrum, including acute gastrointestinal illnesses, haemorrhagic fevers, rodent-borne zoonoses, oncogenic malignancies, and slow-progressing neurodegenerative conditions.
Definition and Significance of RNA Viruses
RNA viruses are infectious agents whose genetic material is encoded in RNA rather than DNA. This fundamental difference confers unique biological properties, such as error-prone replication and genetic variability, facilitating immune evasion and emergence of new strains. RNA viruses are responsible for some of the most challenging infectious diseases, including influenza, HIV, Ebola, and viral gastroenteritis. Their global impact necessitates continuous surveillance, research, and innovation in clinical practice.
Viral Gastroenteritis
Major RNA Viruses Causing Gastroenteritis
Viral gastroenteritis, colloquially known as “stomach flu,” refers to inflammation of the gastrointestinal tract caused by viral agents. The predominant RNA viruses implicated include:
- Rotavirus: Double-stranded RNA virus, leading cause of severe diarrhoea in infants and young children.
- Norovirus: Single-stranded RNA virus, major cause of outbreaks in all age groups, especially in closed communities.
- Astrovirus: Single-stranded RNA virus, causes milder gastroenteritis, particularly in children.
- Sapovirus: Similar to norovirus, causes sporadic cases and outbreaks.
Transmission and Epidemiology
Transmission typically occurs via the faecal-oral route, contaminated water or food, and person-to-person contact. Norovirus outbreaks are common in schools, hospitals, and cruise ships due to high infectivity and environmental persistence. Rotavirus infection is most prevalent in children under five, with seasonal peaks observed in winter months.
Clinical Features
- Acute onset of vomiting and diarrhoea
- Abdominal cramps and low-grade fever
- Dehydration, particularly in infants and elderly
- Self-limiting course, usually resolving within 1–3 days
Management
Management is primarily supportive, focusing on rehydration and electrolyte balance. Oral rehydration solutions (ORS) are the cornerstone of therapy. Vaccination (e.g., rotavirus vaccine) has significantly reduced disease burden. Antiviral agents are generally not indicated for uncomplicated cases.
Ebola Virus Infection
Virology and Classification
Ebola virus belongs to the family Filoviridae, genus Ebolavirus. It is an enveloped, single-stranded negative-sense RNA virus. Several species exist, with Zaire ebolavirus being the most virulent.
Epidemiology
Ebola virus disease (EVD) is endemic to Central and West Africa, with outbreaks often linked to contact with infected wildlife, particularly fruit bats and primates. Human-to-human transmission occurs via direct contact with blood, secretions, or contaminated surfaces.
Clinical Presentation
- Incubation period: 2–21 days
- Initial symptoms: Fever, malaise, myalgia, headache
- Progression: Vomiting, diarrhoea, rash, impaired renal and hepatic function
- Haemorrhagic manifestations: Bleeding from mucous membranes, gastrointestinal tract
- Multisystem organ failure in severe cases
Treatment and Outcomes
Supportive care, including fluid management, electrolyte correction, and organ support, remains the mainstay. Experimental therapies (e.g., monoclonal antibodies, antiviral agents) have shown promise. Case fatality rates vary from 25% to 90%, depending on the virus species and healthcare infrastructure.
Rodent-Borne Viral Infections
Examples and Classification
Rodent-borne RNA viruses are zoonotic pathogens transmitted from rodents to humans, often resulting in severe systemic illness. Notable examples include:
- Hantavirus: Family Bunyaviridae; causes Hantavirus Pulmonary Syndrome (HPS) and Haemorrhagic Fever with Renal Syndrome (HFRS).
- Lassa virus: Family Arenaviridae; responsible for Lassa fever, endemic in West Africa.
- South American arenaviruses: e.g., Junin and Machupo viruses, causing Argentine and Bolivian haemorrhagic fevers.
Transmission
Transmission typically occurs via inhalation of aerosolised excreta (urine, faeces, saliva) from infected rodents, direct contact, or, less commonly, rodent bites. Human-to-human transmission is rare, except for Lassa virus.
Clinical Features
- Fever, myalgia, headache
- Respiratory distress (Hantavirus)
- Renal impairment (HFRS)
- Haemorrhagic manifestations (Lassa, Junin viruses)
- Multiorgan dysfunction in severe cases
Prevention and Control
Preventive strategies include rodent control, improved sanitation, use of protective equipment, and public education. Vaccines are available for some arenaviruses but not for hantavirus. Early recognition and supportive management improve outcomes.
Oncogenic Viruses
Definition and Mechanisms of Oncogenesis
Oncogenic viruses are those capable of inducing cellular transformation and malignancy in the host. RNA viruses may exert oncogenic effects via:
- Insertional mutagenesis: Integration of viral genome disrupts host oncogenes or tumour suppressor genes.
- Expression of viral oncoproteins: Interfere with cell cycle regulation and apoptosis.
- Chronic inflammation: Persistent infection leads to cellular damage and neoplastic transformation.
Examples of Oncogenic RNA Viruses
- Human T-lymphotropic virus type 1 (HTLV-1): Associated with adult T-cell leukaemia/lymphoma.
- Hepatitis C virus (HCV): Linked to hepatocellular carcinoma.
- Human immunodeficiency virus (HIV): Indirectly oncogenic via immunosuppression, leading to increased risk of Kaposi’s sarcoma, lymphomas, and other tumours.
Human Oncogenic Viruses and Associated Malignancies
| Virus | Type | Associated Malignancy | Epidemiology | Mechanism |
| HTLV-1 | RNA (retrovirus) | Adult T-cell leukaemia/lymphoma | Endemic in Japan, Caribbean, parts of Africa | Tax protein induces proliferation, inhibits apoptosis |
| HCV | RNA (flavivirus) | Hepatocellular carcinoma | Global, high prevalence in Egypt, India, China | Chronic inflammation, cirrhosis, genetic instability |
| HIV | RNA (retrovirus) | Kaposi’s sarcoma, non-Hodgkin lymphoma | Worldwide, especially sub-Saharan Africa | Immunosuppression, activation of latent oncogenic viruses (e.g., HHV-8) |
Slow Virus Infections
Definition and Characteristics
Slow virus infections are chronic, progressive diseases caused by unconventional viruses with prolonged incubation periods and gradual clinical deterioration. These infections may be due to classic RNA viruses or atypical agents such as prions.
Examples
- Human Immunodeficiency Virus (HIV): Progressive immunodeficiency leading to AIDS, with long asymptomatic phase.
- Measles virus (Subacute Sclerosing Panencephalitis, SSPE): Rare, fatal neurodegenerative disease following measles infection.
- Prion diseases (e.g., Creutzfeldt-Jakob disease): Although prions lack nucleic acid, they share the slow progression characteristic.
Pathogenesis
Slow virus infections typically involve persistent replication or latency, immune evasion, and gradual tissue destruction. HIV targets CD4+ T cells, leading to immune collapse over years. SSPE results from defective measles virus replication in the brain, causing neuronal loss.
Clinical Course
- Prolonged asymptomatic phase
- Gradual onset of symptoms (e.g., cognitive decline, motor deficits, immunosuppression)
- Progressive deterioration and eventual fatality
Summary of RNA Virus Infections
| Virus | Family | Transmission | Major Disease(s) | Clinical Features | Outcome |
| Rotavirus | Reoviridae | Faecal-oral | Gastroenteritis | Diarrhoea, vomiting, dehydration | Usually self-limited, severe in infants |
| Norovirus | Caliciviridae | Faecal-oral, person-to-person | Gastroenteritis | Vomiting, diarrhoea, abdominal pain | Self-limited, outbreaks common |
| Ebola virus | Filoviridae | Contact with body fluids, wildlife | Haemorrhagic fever | Fever, bleeding, organ failure | High mortality (25–90%) |
| Hantavirus | Bunyaviridae | Rodent excreta | Pulmonary syndrome, renal syndrome | Fever, myalgia, respiratory distress | Variable, can be fatal |
| Lassa virus | Arenaviridae | Rodent excreta, person-to-person | Haemorrhagic fever | Fever, bleeding, shock | High morbidity, variable mortality |
| HTLV-1 | Retroviridae | Blood, sexual, vertical | Leukaemia/lymphoma | Lymphadenopathy, organ infiltration | Chronic, often fatal |
| HCV | Flaviviridae | Blood, sexual | Hepatitis, carcinoma | Chronic hepatitis, cirrhosis | Chronic, risk of cancer |
| HIV | Retroviridae | Blood, sexual, vertical | AIDS, associated cancers | Immunodeficiency, opportunistic infections | Chronic, fatal without treatment |
Conclusion
Miscellaneous RNA virus infections encompass a wide array of clinical presentations, ranging from acute self-limited illnesses to chronic, fatal diseases and oncogenic malignancies. The high mutation rates and adaptability of RNA viruses pose ongoing challenges for diagnosis, treatment, and prevention. Notable examples include viral gastroenteritis agents (rotavirus, norovirus), haemorrhagic fever viruses (Ebola, Lassa), rodent-borne pathogens (hantavirus), and oncogenic viruses (HTLV-1, HCV, HIV). Slow virus infections, such as HIV and SSPE, highlight the insidious nature of certain RNA viruses.
Future research directions should focus on improved surveillance, vaccine development, antiviral therapies, and understanding the molecular mechanisms of pathogenesis and oncogenesis. Interdisciplinary collaboration among clinicians, researchers, and public health authorities is essential to mitigate the impact of these formidable pathogens and to advance scientific knowledge.
Key Takeaways
- RNA viruses are a major cause of human disease due to their genetic variability and adaptability.
- Clinical spectrum includes gastroenteritis, haemorrhagic fevers, respiratory and renal syndromes, oncogenic malignancies, and slow-progressing infections.
- Management strategies vary from supportive care to targeted antivirals and vaccines, with prevention remaining paramount.
- Understanding disease mechanisms and epidemiology is critical for effective control and future research.
REFERENCES
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- Joanne Willey, Prescott’s Microbiology, 11th Edition, 2019, Innox Publishers, ASIN- B0FM8CVYL4.
- Anju Dhir, Textbook of Applied Microbiology including Infection Control and Safety, 2nd Edition, December 2022, CBS Publishers and Distributors, ISBN: 978-9390619450
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