Medical Microbiology & Immunology

Medical Microbiology & Immunology

Lecture 21 Virology Viruses of Mumps, Measles, Rubella and other Childhood Exanthems

1. 
   To know the viruses that cause childhood exanthems.
   

Mumps (Paramyxoviridae), Measles (Paramyxoviridae), Rubella (Togaviridae), Erythema infectiosum (Parvoviridae), and Roseola Infantum (rose-colored rash).

2. 
   To describe the unique features of each virus.
   

Mumps (Paramyxoviridae) – (-)ssRNA virus, nucleoprotein complex surrounded by matrix, envelope contains two spikes (one w/H and N, the other is F), replicates and is assembled in the cytoplasm, and buds through cytoplasmic membrane. Pleomorphic.

Measles (Paramyxoviridae) - structure and replication are the same as mumps but the envelope protein of measles lacks neuraminidase (N) activity.

Rubella (Togaviridae) - simple, icosahedral, enveloped virus, (+)ssRNA, single species of capsid protein, entry by receptor mediated endocytosis, translated to produce proteins including RNA dependent RNA polymerase, protein synthesize replicative intermediates, and virus assembly may take place at Golgi complex or plasma membranes.

Erythema infectiosum (Parvoviridae) - a moderately benign contagious epidemic disease in children, human parvovirus B19, small (20-25 nm), icosahedral ssDNA virus, replicates and assembles in the nucleus of dividing cells, released by cell disruption.

Roseola Infantum (rose-colored rash) – Agent (?) human herpes virus type 6, adenovirus, coxsackievirus, or echoviruses. Common disease in infants and children (6 months -4 years).

3. 
   To explain the clinical disease associated with each virus.
   

Virus	Clinical Disease
Mumps	Viruses breathed in and replicates in the respiratory tract epithelium and local lymph nodes, it then spreads throughout the body, around day 16-18 a fever develops, followed by painful swelling of one or both parotid glands (parotitis). Symptoms last 7-10 days, immunity is lifelong. Common complications: meningitis, encephalitis (hearing loss), pancreatitis, orchitis, oophortis, and myocarditis (less common).
Measles	Enters respiratory tract, replicates, spreads to local lymph nodes, and eventually is transported to all body organs. Incubation is 7-18 days. Koplik spots first appear in the mouth as small bluish yellow spots 1-2 days before rash, which appears on head, then trunk and extremities. High fever, delirium, cough, photophobia, and conjunctivitis. Complications: encephalitis (death or permanent impairments), bacterial superinfection (otitis media, mastoiditis, pneumonia, sinusitis), death.
Rubella	Virus breathed in and replicates in respiratory tract, spreads to lymph nodes, and viremia develops. Incubation 14-21 days. Mild fever with rash, which appears on head neck and trunk (may be mild), symptoms persist 1-3 days, contagious seven days before and after rash, immunity is lifelong.
Erythema infectiosum	Mild fever, headache, and rash may occur on face and persist 1-2 weeks.
Roseola Infantum	Abrupt onset of fever, brief convulsions, after 3-5 days fever goes down followed in few hours by faint, transient rash. Rosette on face and body (echo 19), finger (hand and mouth-coxsackie virus A.

4. 
   To describe the diagnosis, treatment, and preventions of mumps, measles, rubella and other viral exanthems.
   

Virus	Diagnosis	Treatment and prevention
Mumps	Clinical picture (most common), virus isolation (saliva, urine), serology	Treatment: supportive Prevention: live, attenuated vaccine after 1st year of life or adults (particularly men).
Measles	Clinical picture (most common), virus isolation (throat, urine), serology	Treatment: supportive Prevention: live, attenuated vaccine 13-15 months of age
Rubella	Isolate virus, hemagglutination inhibition (most common)	Treatment: supportive Prevention: live attenuated vaccine after 1st year, not given in pregnancy or immunocompromised patients.
Erythema infectiosum	"Fifth disease" Clinical picture	Treatment: supportive
Roseola Infantum	Clinical picture	Treatment: supportive