Replication of paramyxoviruses

Replication of paramyxoviruses:
Very similar for all viruses in this group. Unlike influenza, all the action occurs in the cytoplasm. However, the overall strategy very similar to influenza, although unlike influenza, Paramyxovirus replication is resistant to actinomycin D.

 
A large excess of nucleocapsids are produced in infected cells, which form characteristic cytoplasmic inclusion bodies. Syncytium formation is quite common (F glycoprotein).
Parainfluenzaviruses 1-4:
Cause acute respiratory infections of man ranging from relatively mild influenza-like illness to bronchitis, croup (narrowing of airways which can result in respiratory distress, due to swelling of the larynx and related structures ) and pneumonia; common infection of children. Transmitted by aerosols. Little serological variation, therefore rare infection in adults
Treatment & Prevention:The antiviral drug ribavrin has been used that blocked the capping the viral mRNA which can be prevented by the used of subunit vaccine & live attenuated vaccine





Mumps:

Recognized by the ancient Greeks, virus first isolated in 1934. Haemagglutination is a valuable assay technique for this virus. Humans are believed to be the only natural reservoir for the virus (possibly primates). Transmission via saliva and respiratory secretions; less infectious than measles/chickenpox - more adult cases.
Symptoms: typically causes painful swelling of parotid glands 16-18 days after infection. This is preceded by primary replication of the virus in epithelial cells of the URT and local lymph nodes, followed by viraemia. .
· Prevention: one invariant serotype therefore vaccines are viable - both formalin-inactivated and live attenuated exist, the latter now being widely used
Treatment: none (passive immunization has been used).
Measles:

Measles virus is believed to have evolved from rinderpest (or a similar animal virus) 4000-5000 years ago - when Babylonian cities grew large enough to support continuous person-to-person transmission and thus maintain the virus. One of the most infectious diseases known! ~500,000 deaths in children in the third world - part of the W.H.O. expanded programme of immunization. Childhood infection almost universal, protection resulting from this is probably lifelong. Both man and wild monkeys are commonly infected, but the virus can also infect rodents (in wild?). In culture, produces characteristic intranuclear inclusion bodies and syncytial giant cells. Transmission and initial stages of disease similar to mumps, but this virus can also infect via the eye and multiply in the conjunctivae. Viraemia following primary local multiplication results in widespread distribution to many organs.
Symptoms: After a 10-12 day incubation period, dry cough, sore throat, conjunctivitis (virus may be excreted during this phase!), followed a few days later by the characteristic red, maculopapular rash and Koplik s spots - raised red spots with white centres in the mouth..
Complications include bronchopneumonia and otitis media (with or without secondary bacterial infections) (relatively common), and encephalitis.
Subacute schlerosing pan encephalitis (SSPE).
Treatment: Vitamin A & The antiviral drug ribavrin has been used
Prevention: Both live and killed vaccines exist.
 
Respiratory syncytial virus (RSV):

RSV was first isolated in 1956 and subsequently recognized as a major cause of L.R.T. disease in infants and young children. causing bronchitis, pneumonia and croup. RVS has been suggested as a possible factor in cot death and asthma.
RSV may be linked to epidemics of asthma and has been identified as an exacerbating factor in nephrotic disease, cystic fibrosis, and opportunistic infections in the immunocompromised. Bone marrow transplant patients develop lower respiratory tract disease with RSV,).
 Treatment & Prevention:The antiviral drug ribavrin has been used  Currently no effective vaccine
Human Metapneumovirus (HMPV):
HMPV was first isolated from children in the Netherlands and assigned to the pneumovirus genus on the basis of clinical data, sequence homology and gene organization. HMPV produces RSV-like illnesses in children, ranging from upper respiratory tract disease to severe bronchiolitis and pneumonia.). All recent data suggests that hMPV infections are not limited to young children or to the upper respiratory tract and that this virus causes severe lower respiratory tract diseases in high-risk subjects.

Nipah and Hendra Viruses:
Nipah and Hendra viruses have emerged as new pathogens in Malaysia and Australia respectively in recent years: