RNA Viruses: Paramyxoviridae and Rubella Virus

RNA Viruses: Paramyxoviridae and Rubella Virus

• RNA viruses are a large group, some enveloped, some unenveloped
• Paramyxoviruses and Rubella virus are specific examples
• Paramyxoviruses have a single-stranded, negative-sense, nonsegmented RNA genome
• Rubella virus has a single-stranded, positive-sense RNA genome
• Both viruses have an outer envelope
• RNA viruses carry their own RNA-dependent RNA polymerase
• Negative-stranded RNA viruses must convert their negative-sense RNA to positive-sense mRNA
• Two subcategories of negative-polarity RNA viruses exist: those with a single RNA piece, or those with multiple RNA pieces
• Paramyxoviruses contain 6 structural proteins in complex with viral RNA to form a nucleocapsid
• Paramyxoviruses have a helical nucleocapsid with an outer lipoprotein envelope with spikes (which include fusion protein, hemolysin activity, neuraminidase, etc.)
• Paramyxoviruses genomes are not infectious
• Measles virus, parainfluenza viruses, mumps virus etc are specific examples of paramyxoviruses
• Rubella virus has one type of antigen
• Both viruses are spread through the respiratory route
• Rubella can cause congenital disease (CRS) in the developing fetus, while Paramyxoviruses cause symptoms in an individual

Paramyxoviruses

• Contain a single, nonsegmented, negative-sense RNA molecule
• Contain 6 structural proteins (N/NP, P, L, M, F, HN/H/G)
• The F protein mediates cell-membrane fusion
• The HN/H/G protein plays role in host attachment
• Cause respiratory tract disease
• May cause complications like encephalitis, meningitis, subacute sclerosing panencephalitis
• The viral genome is not directly infectious

Rubella Virus

• Has a single-stranded, positive-sense RNA genome
• Causes a mild infection in healthy individuals
• The primary concern is the potential for congenital birth defects (CRS) if a pregnant woman contracts the virus
• The virus can cross the placenta
• Causes congenital rubella syndrome (CRS)
• Characterized by a rash and lymphadenopathy,
• Symptoms resolve within 3 days
• Symptoms include: Fever, rash, lymphadenopathy, arthralgia
• Causes fetal complications, including deafness, heart defects, eye cataracts etc if a pregnant woman contracts it during the first trimester of pregnancy

Mumps Virus

• A paramyxovirus
• Characterized by swelling of the salivary glands, particularly the parotid glands.
• Can lead to complications, including pancreatitis, encephalitis, and orchitis (testicular swelling) in males (which may lead to sterility)
• Airborne transmission, with an incubation period of 14-21 days
• Recovery is usually complete with no long-term effects

Respiratory Syncytial Virus (RSV)

• A paramyxovirus
• Causes respiratory infections, especially in infants and young children
• Infections in infants can be severe, with possible pneumonia or bronchiolitis
• A common cause for acute respiratory infections and death in the first year of life
• Causes syncytia formación
• Spread via droplets and direct contact .
• Has a single serotype
• The virus replicates in the nasopharynx and local lymph nodes

Measles

• A paramyxovirus
• Highly contagious
• Characterized by fever, cough, runny nose, and a distinctive rash
• Symptoms include: fever, conjunctivitis, respiratory symptoms, koplik spots
• Spread respiratory droplets
• Leads to complications like encephalitis, pneumonia and subacute sclerosing panencephalitis
• Has a single serotype