Paramyxoviridae Study Guide

Paramyxoviridae All of the viruses of the Paramyxoviridae family are spread through the respiratory route and are highly contagious. Morphology ssRNA viruses Nonsegmented Enveloped Hemagglutinin Fusion Viral organisation PARAMYXOVIRUS FAMILY properties of attachment protein GLYCOPROTEIN HN TYPICAL MEMBERS mumps virus parainfluenza virus H measles virus G respiratory syncytial virus Paramyxoviruses 1.Classification Paramyxovirus (parainfluenza viruses and mumps virus) cotains neuraminidase and hemagglutinin The family Paramyxoviridae consists 3 important genera: Pneumovirus (respiratory syncytial virus) lacks hemagglutinin and neuraminidase. Morbillivirus (measles virus) is distinguished by the absence of neuraminidase in the virions. Multiplication:  Absorption  Penetration  Uncoating  Production of, positive-sense complementary RNA Transcription of virion RNA.  Translation of viral proteins.  Assembly  Budding through the cell membrane incorporating part of the cell membrane into their envelope. Parainfluenza Viruses The taxonomic division  forming four major serotypes : 1) Human parainfluenza virus type 1 (most common cause of croup) 2) Human parainfluenza virus type 2 (causes croup and other upper and lower respiratory tract illnesses) 3) Human parainfluenza virus type 3 (associated with bronchiolitis,pneumonia and lower respiratory tract illnesses) 4) Human parainfluenza virus type 4 (These viruses are not known to cause any human illness) Paraflu: Epidemiology • • • • occurs worldwide usually endemic primarily in young children reinfections common • No vaccine is available for Parainfluenza Treatment Supportive Fluids, oxygen, respiratory support, bronchodilators Antiviral Agents Ribavirin Respiratory syncytial virus RSV- syncytium formation RSV Diseases • Bronchiolitis – droplet inhalation through the nose • Asthma • Pneumonia – Chronic Obstructive Pulmonary Disease An x ray of a child with RSV Spread through respiratory secretions - coughing, sneezing Symptoms • • • • Occurs within either days or hours of exposure vary from person to person symptoms most severe in children under the age of two symptoms in adults and children are mild – – – – – – Stuffy Nose Nose flaring Low-grade fever Wheezing Rapid Breathing Ear Infection www.istockphoto.com/file_closeup/ Treatment • Currently no RSV vaccine available • No treatment given in mild disease – just medication to reduce fever • Oxygen therapy and mechanical ventilation • Ribavirin aerosol (severe disease) – Sometimes used---IGIV (immune globulin intravenous) with RSV-IGIV (neutralizing RSV antibody) and Ribavirin. Epidemiology • Transmission – RSV is easily transmitted via larange, aerosolized respiratory particles, or through contact with nasal secretions. – The most common sites of innoculation are the eyes and nose • Prevalence – Winter –spring months – Most frequently transmitted between family members and hospitals – The incubation period is three to five days for most patients MEASLES - RASH Generalized, maculopapular, erythematous rash. Measles is an acute, highly infectious disease characterized by a maculopapular rash, fever, and respiratory symptoms. Murray et al. Medical Microbiology • Measles Pathogenesis – Infection via respiratory route – Virus replicates in epithelium of upper respiratory tract – Spreads to lymph nodes • Further replication occurs here – Spreads to all parts of the body – Skin rash is due to effects of virus replication within skin cells Generalized Erythematous Rash. MEASLES - Koplik’s spots Murray et al. Medical Microbiology Measles Disease  Acute febrile illness, mostly in childhood  Incubation period: 10 – 14 days  Onset is flu-like: high fever, cough, conjunctivitis  Koplik's spots: red spots with bluish-white centre on the oral mucosa  1 – 2 days later, acute symptoms decline with appearance of a widespread maculopapular rash  Over 10 – 14 days, recovery is usually complete as the rash fades Pathogenesis and Immunity MEASLES GIANT CELL PNEUMONIA  In culture, produces characteristic intra nuclear inclusion bodies and syncytial giant cells.  Viraemia following primary local multiplication results in widespread distribution to many organs. Complications  Giant cell pneumonia, more common in adults  Otitis media  Post-measles encephalitis – Deafness – mental disorders  Subacute sclerosing panencephalitis (SSPE): progressive and fatal degenerative disease within the infected cells, there is a defective form of the virus is not released as complete virus from the cells. It can be a result of a mutation of the virus itself. Rare (decrease since vaccination program) Measles Epidemiology • Reservoir • Transmission Human Respiratory Airborne • Temporal pattern Peak in late winter–spring • Communicability 4 days before to 4 days after rash onset Mumps • Causative Agent – Mumps virus – Member of the Paramyxoviridae family • Symptoms – Early symptoms The appearance of the patient as a result of parotid gland swelling seems to be in grin. • Fever with loss of appetite and headache – Later symptoms • Painful swelling of one or both parotid glands and spasms • Usually makes it difficult to chew and swallow – Symptoms disappear in about a week Mumps Pathogenesis • Respiratory transmission of virus • Incubation period 14-28 days • Replication in nasopharynx and regional lymph nodes • Viremia 12-25 days after exposure with spread to tissues • Multiple tissues infected during viremia. Mumps Pathogenesis • Infection via respiratory route • Virus replicates in epithelium of upper respiratory tract • • • • • viremia spreads to glands & nervous tissue inflammation & cell death The contagiousis period  from about 4 days before to about a week after the onset of symptoms. Mumps Clinical Features painful enlargement of one or both of the parotid (salivary) glands (Parotid swelling) orchitis Inflammation of the ovary and pancreas can also occur. Aseptic meningitis (usually resolving without problems) Ear ache Disease is usually self-limiting within a few days Mumps Complications CNS involvement Orchitis Pancreatitis Deafness Death Epidemiology Mumps occurs throughout the world. Endemically occurs throughout the year. Outbreaks occur where crowding favors dissemination of the virus. The disease reaches its highest incidence in children age 5-15 years, but epidemics occur in army camps. Although morbidity rates are high, the mortality rate is low. Humans are the only known reservoir of virus. The virus is transmitted by direct contact, airborne droplets. Prevention of Disease • Active Immunization vaccines • Passive immunization (immunoprophylaxis) Pooled hyperimmune globulin Monoclonal antibodies Preventing Spread • Handwashing • Disinfection of surfaces • Gloves, masks, goggles, gowns • Isolation, and cohort nursing • Immunization MMR Vaccine Live attenuated strains of : 1. Measles virus 2. Mumps virus 3. Rubella virus (Belong to Togaviridae) Age 12-15 months Vaccines Note MMR -1 Deep subcutaneous injection into the upper arm. 2nd dose 4-6 years MMR -2 Deep subcutaneous injection into the upper arm.