Paramyxoviruses

pathogenic paramyxoviruses Measles virus Parainfluenza viruses Mumps virus Respiratory syncytial virus,RSV

paramyxoviruses Spherical ,enveloped, 150~300nm in diameter helical nucleocapsid -ssRNA as a single piece Membrane fusion leads to the formation of syncytia Envelope contains two glycoproteins, F protein and HN/H/G

PARAMYXOVIRUSES pleomorphic HN/H/G glycoprotein SPIKES F glycoprotein helical nucleocapsid (RNA plus NP protein) lipid bilayer membrane polymerase (2 proteins) M protein

Measles virus

HA,HL Multinucleated giant cell syncitia

Pathogenicity and immunity There are only one serotype of virus Measles is an acute febrile illness,mostly in childhood Incubation period:10-12 days Two viraemia High fever,photophobia

conjunctivitis, rhinitis, cough---three main prodrome Koplik’s spots Maculopapular rash---T cell-mediated immunopathological mechanism Rash fades with considerable desquamation

MEASLES - Koplik’s spots

                                                      CDC - B.Rice

MEASLES - RASH CDC - B.Rice

Recovery--- T cell response T cell deficient, may be no rash, may be severe disease (life threatening) Life-long immunity (protective antibody)

High risk factors vitamin A deficient low mucosal defense malnourishment impaired immunity Immunocompromised Adults infection Poor medical care lack of vaccination poor hygiene

Mims et al., Medical Microbiology 1993

Complications pneumonia due to secondary bacterial infection Measles encephalitis SSPE

Laboratory diagnosis Most cases of measles are diagnosed clinically Virus isolation Serodiagnosis ELISA,HI,CF Immunofluorescence assay

Epidemiology Human are only natural host Transmission is person-to-person by respiratory droplet Most contagious before rash is evident Almost all infected individuals show disease Natural infection and vaccine using give life long protection

Prevent and treatment Live attenuated vaccine Can cause problems in immunosuppressed Immune serum globulin Supportive care

Mumps virus

There is only one serotype. Mumps is a world-wide disease,with humans the only known reservior. Most infections are in school-age children. Mumps are often subclinical.

The incubation period is 14-18 days. usually “flu-like” illness,with fever and malaise parotid pain and swelling over a period of 1 to 3 days. The pain gets worse when the child swallows, talks, chews, or drinks acidic juices (like orange juice).

Clinical meningitis remains the most serious complication of mumps,occurring in 1-10% of patients with mumps parotitis. postpubertal males --- orchitis Oophoritis also occurs in girls

Infection appears to confer life-long immunity and second infections do not occur. Typical mumps does not usually require laboratory confirmation. Mumps live attenuated virus

Parainfluenza viruses

There are four types of parainfluenza viruses. The viruses may cause minor upper respiratory tract illness,as well as tracheitis,laryngitis,bronchiolitis and pneumonia. Local infection and no viraemia. Fatalities are rare and reinfections occur

Respiratory syncytial virus(RSV)

The most serious illness caused by RS virus is bronchiolitis in young babies,especially in those under 1 year of year.

This infection is potentially life-threatening, particularly in those with bronchopulmonary dysplasia or congenital heart defects. In older children and adults,the virus causes only minor infections RS virus causes a substantial winter epidemic every year. No vaccines have proved satisfactory.

Rhinovirus The most frequent of all human infections Piconaviridae Spherical, non-enveloped,+ssRNA Acid lability(complete inactivation at Ph 3.0) Over 100 serotypes

The typical illness is a generally referred to as a common cold. Infections provoke poor response and reinfections are very common.

Rubella virus glycoprotein icosahedral nucleocapsid RNA (single-stranded positive-sense) lipid bilayer membrane

Rubella virus(German measles) Biological characters Togaviridae Spherical, 50-70nm +ssRNA, enveloped Icosahedral symmetry One serotype

Pathogenicity and immunity Infection is common in childhood Infection in the upper respiratory tract viraemia the target organs such as skin and joints

Pathogenicity and immunity Incubation period:2-3 weeks Fever, cough, arthritis The characteristic feature is a macular rash and lymphadenopathy

Pathogenicity and immunity Complications:encephalitis and thrombocytopenia High risk factor: pregnancy infection during the first trimester congenital rubella Life-long lasting immunity after infection

Rubella rash

Congenital rubella Congenital rubella symdrome Hearing loss Congenital heart defects Neurological Psychomotor and/or mental retardation Ophthalmic cataract, glaucoma, retinopathy

Congenital rubella The risk to the fetus depends on the gestational period. First trimester 65-85% of neonates have sequelae Reinfection in pregnant women leads little effect on fetus.

Prevention Live attenuated vaccine Susceptible non-pregnant females In UK , MMR vaccine to all children at 15 months of age

Adenovirus

Named from their original source, adenoid tissue Human adenoviruses are subdivided into 6 subgenera (A-F) and 49 recognized serotypes.

Biological character A single piece of dsDNA ,non-enveloped,70-90nm in diameter A very good example of an icosahedron apical fiber projects from each pentron function: type-specific haemagglutination(monkey or rat erythrocytes) Experimentally induce transformation of hamster cells in culture.But there is no evidence that this can occur in humans.

Pathogenicity Respiratory disease conjunctivitis gut infections

Treatment and control No satisfactory vaccine No antiviral drugs