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 VIROLOGY - LECTURE 
 FIFTEEN  
 RUBELLA (GERMAN 
 MEASLES) VIRUS  

Virology Lecture 1
BASIC VIROLOGY: DEFINITIONS, CLASSIFICATION, 
MORPHOLOGY AND CHEMISTRY  

Virology Lecture 2
 
 DNA VIRUS REPLICATION 
 STRATEGIES  

 RNA VIRUS REPLICATION
 STRATEGIES  

 ONCOGENIC VIRUSES 
 
 SEVEN  HUMAN  
 IMMUNODEFICIENCY VIRUS  
 AND AIDS  

 PICORNAVIRUSES - 
 PART ONE  
 ENTEROVIRUSES  
Virology Lecture 

 HERPES VIRUSES  

Virology Lecture 9

INFLUENZA VIRUS

Virology Lecture 10

MEASLES (RUBEOLA) 
AND MUMPS VIRUSES  

Virology Lecture 11
RUBELLA (GERMAN 
 MEASLES) VIRUS

Virology Lecture 12
RABIES  




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  VIROLOGY - LECTURE FIFTEEN  

  RUBELLA (GERMAN MEASLES) VIRUS  

Dr. Margaret Hunt 

MEDICAL MICROBIOLOGY, MBIM 650/720  LECTURE: 70 (part)
READING: Murray et al., Microbiology, 3rd Ed., Chapter 59 pp. 499-502

TEACHING OBJECTIVES

Brief review of structure and properties of rubella virus. Discussion of viral pathogenesis and disease, epidemiology, prevention and treatment.

 

INTRODUCTION

Infections with measles, mumps and rubella viruses are confined to man and occur worldwide. They are all spread primarily via the aerosol route. Each of these viruses exists as a single serotype. MMR vaccine contains live, attenuated forms of all three of these viruses.

Rubella virus is a member of the Togavirus family. Mumps and measles viruses are members of the Paramyxovirus family.

 

  RUBELLA  

 Rubella (means "little red" also known as German measles) is a mild disease in children and adults, but can cause devastating problems if it infects the fetus, especially if infection is in the first few weeks of pregnancy.

rubella.jpg (31913 bytes)  Electron micrograph of rubella virus CDC/Dr. Erskine Palmer 

rub1.jpg (54454 bytes)  Structure of rubella virus

THE VIRUS

Rubella virus is the only member of the Rubrivirus genus of the Togavirus family.
Unlike most Togaviruses it is NOT arthropod borne, but is acquired via the respiratory route.
It is an enveloped (toga=cloak), non-segmented, positive sense, RNA virus and replicates in the cytoplasm.
Its nucleocapsid has icosahedral symmetry.

There is only one major antigenic type.

 

PATHOGENESIS AND DISEASE:

rubelpath.jpg (40356 bytes)

CLINCAL ASPECTS OF RUBELLA

Site of replication of virus

Symptoms

Notes

Respiratory tract

Minor symptoms although virus is shed (Mild sore throat, coryza, cough)

Patient is infectious 5 days before to 3 days after symptoms

Skin

Rash 
rubel2.jpg (27265 bytes)
 
Rash of rubella on skin of child's back. Distribution is similar to that of measles but the lesions are less intensely red. CDC

rubel3.jpg (54360 bytes) Infant with congenital rubella and "blueberry muffin" skin lesions.
Lesions are sites of extramedullary hematopoiesis
and can be associated with several different congenital viral infections and hematologic diseases. CDC

rubel4.jpg (45996 bytes) Face of adult with rubella. CDC/Barbara Rice 
ber2@cdc.gov 

Often short-lived, atypical; immunopathology (Ag-Ab complexes)

Lymph nodes

lymphadenopathy

Commoner in posterior triangle of neck or behind ear

Joints

mild arthralgia, arthritis

Immunopathology (circulating immune complexes)

Placent/fetus

Placentitis
Fetal damage

rubel-baby.jpg (29090 bytes) Baby born with rubella: Thickening of the lens of the eye that causes blindness (cataracts)  CDC

Congenital rubella

Adapted from Mims et al. Medical Microbiology, 1993, Mosby.

 

CHILDREN AND ADULTS

Man is the only host. Virus is spread via an aerosol route and occurs throughout the world.

Initial site of infection is the  upper respiratory tract. The virus replicates locally (epithelium, lymph nodes) leading to viremia and  spread to other tissues. As a result the disease symptoms develop.

Rash (if it occurs) starts approximately 2 weeks after initial infection. There is probably an immunological basis for rash (since it occurs as antibody titers rise). The  patient is infectious from about 1 week before onset of rash to about 1 week after. Disease results in low grade fever, rash, sore throat, lymphoadenopathy. Maculopapular rash begins on the face and lasts from 12hr to 5days. Some individuals (especially adults and especially women) get arthralgia and sometimes arthritis which usually clears up in a few weeks.

Recovery

T-cell immunity plays an important role in recovery. IgM may persist for up to a year. There are also IgG, IgA responses.

Complications

Complications are extremely rarely (1 in 6000 cases) - rubella encephalopathy (headache, vomiting, stiff neck, lethargy, convulsions) may occur about 6 days after rash. It usually lasts only a few days and most patients recover (no sequelae),. If death occurs, it is within few days of onset of symptoms.

 

FETUS

The risk to a fetus is highest in the first few weeks of pregnancy and then declines in terms of both frequency and severity, although there is still some risk in second trimester. Virus infects the placenta and then spreads to the fetus.
If non-immune mothers are infected in the first trimester, up to 80% of neonates may have sequelae:

hearing loss

congenital heart defects

neurologic problems (psychomotor retardation, mental retardation)

ophthalmic problems (cataract, glaucoma, retinopathy)

intrauterine growth retardation

thrombocytopenia purpura

hepatomegaly

splenomegaly

There may also be variety of other problems including bone lesions, pneumonitis etc..

In most cases, there is neural involvement - lethargy, irritability, motor tone problems, mental retardation, motor disabilities, abnormal posture, neurosensory hearing loss.

Virus from congenital infections persists after birth. Those with congenital infections can infect others after birth for a year or more. Virus occurs in naso-pharyngeal secretions, urine and feces.

Later on, patients with congenital rubella syndrome may develop additional complications including diabetes mellitus (up to 20%), thyroid dysfunction, growth hormone deficiency, ocular complications.

Progressive rubella panencephalitis

This is an extremely rare slow virus disease. It usually develops in the teens with death within 8 years. Most often it is associated with congenital rubella and may be associated with childhood rubella.

 

DIAGNOSIS OF RUBELLA

Many (possibly 50%) infections are apparently subclinical and many infections go unrecognized, even if symptoms develop (rash is not always present).

Infections with many other agents give similar symptoms to rubella (e.g. infection with human parvovirus, certain arboviruses, many of the enterovirus group of picornaviruses, some adenoviruses, EBV, scarlet fever, toxic drug reactions).

Serological tests or isolation of virus (immunofluorescence) are needed to confirm infection of individual.


EPIDEMIOLOGY

Man is the only host.
Rubella occurs world wide.
Periodic epidemics occur in an unvaccinated population.
Natural infection protects for life (there is a single serotype).

PREVENTION

A live vaccine (attenuated strain) is available. Since only one serotype, a univalent attenuated vaccine can provide lifelong immunity. The vaccine strain does not spread to family members.

It is important that women are vaccinated prior to their first pregnancy. United States recommendations are for childhood vaccination to prevent epidemics, combined with vaccination of susceptible, non-pregnant adolescent and adult females. The vaccine is contraindicated for pregnant women, but when unwittingly used, no problems have been seen. If the patient is pregnant and seronegative, the pregnancy should be monitored carefully and the patient vaccinated postpartum.

TREATMENT

There is no specific treatment. Supportive care should be used


 

 


 






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