RNA Viruses Overview and Transmission Patterns

RNA Viruses Overview

• RNA viruses use RNA as their genetic material, differing from DNA viruses.
• They are classified into different families based on their structure, genome characteristics, and replication strategies (different types of RNA and their genomes).
• Many RNA viruses are enveloped, meaning they have a lipid membrane surrounding their nucleocapsid.
• Some common families include Picornaviridae, Rhabdoviridae, Flaviviridae, Retroviridae, and Orthomyxoviridae.

Arboviruses and Rodent-Borne Viruses

• Arboviruses and rodent-borne viruses are often transmitted by arthropods (insects) and rodents.
• Some specific examples and the vectors that transmit them, including mosquitoes, ticks, and sandflies, are presented in the text.
• Different families like Arenaviridae, Bunyaviridae, Filoviridae, Flaviviridae, Reoviridae, and Togaviridae, are included as examples of viral classifications important for understanding patterns of transmission and diseases.
• Important diseases associated with these families and vectors discussed include various encephalitis types, hemorrhagic fevers, and other illnesses.
• Dengue fever, Japanese B encephalitis, Zika virus, and other examples of diseases caused by these families of viruses are discussed.

Dengue Virus

• Dengue viruses are transmitted by the Aedes mosquito.
• Four serotypes of dengue virus exist (DENV 1–4).
• Infection with one serotype generally does not provide lifetime immunity to the others.
• Secondary infection may lead to life-threatening complications (Dengue Hemorrhagic Fever)
• Symptoms, such as fever, headache, muscle, and joint pain, and rash are listed in the document
• Diagnosis involves laboratory tests like NS1, IgM and IgG levels, PCR and other tests
• Prevention includes mosquito control measures, vector control
• Vaccine (Dengvaxia) is mentioned as a treatment but only for people who have had prior dengue exposure.
• Risk of severe disease exists if a person gets Dengvaxia without prior dengue infection

Japanese Encephalitis Virus (JEV)

• Transmitted by mosquitoes (genus Culex),
• Often affecting children, causes severe neurological complications (encephalitis).
• Prevention includes mosquito control and vaccination in high-risk areas
• Symptoms, such as high fever, headache, neck stiffness, nausea/vomiting, disorientation are presented.
• Diagnosis includes serum/CSF ELISA, MRI
• Prevention includes reducing mosquito habitats and vaccination.

Zika Virus

• Transmitted by Aedes mosquitoes, (same as Dengue).
• Associated with severe birth defects (like microcephaly) in infants.
• Symptoms, such as fever, rash, and joint pain.
• Diagnosis and prevention are mentioned.

HIV (Human Immunodeficiency Virus)

• Retrovirus
• Transmitted through bodily fluids—most effectively through sexual contact and shared needles.
• It attacks the immune system leading to AIDS (Acquired Immunodeficiency Syndrome).
• The genome is an (+) strand RNA, but the genetic material is replicated as a DNA strand
• It has an enveloped structure.
• Target cells include macrophages and T-helper lymphocytes.
• Diagnosis is through tests like ELISA and Western Blot
• Treatments can include antiretroviral therapies.

Influenza Virus

• Characterized by antigenic drift (minor changes in viral proteins) and antigenic shift (major changes in viral proteins.)
• Causes annual outbreaks of seasonal influenza.
• Classification involves RNA segments.
• Subtypes (A, B, C).
• Prevention involves vaccination.

Rabies Virus

• Transmitted through the bite of an infected animal (e.g., dogs, bats)
• Attacks the central nervous system (CNS).
• Severe disease leading to death if not treated.
• Symptoms involve a progressive neurological syndrome.
• Treatment is most effective if administered quickly after exposure and may involve vaccination series.
• Symptoms, such as aggressive behavior, seizures, and paralysis.
• Diagnosis methods include finding Negri bodies in brain tissue.

Coronavirus (SARS-CoV-2, etc.)

• A class of enveloped RNA viruses that cause respiratory illness.
• Spike protein (S) protein interacts with host ACE2 receptors.
• Transmission via respiratory droplets and fomites.
• Infections can exhibit various severity levels- from mild to severe.
• Treatments include various therapeutic approaches depending on the severity of symptoms.

Other RNA Viruses

• Other RNA viruses (from the text) are also grouped by family and genus.
• Symptoms and the methods of transmission vary for each type of RNA virus.