ID2-MB-3-Paramyxoviruses.pdf

University of Baghdad
College of Medicine
2022-2023
Title: Measles and rubella
Grade: 3rd stage
Module: ID
Speaker: Dr. Hiba Sabah Jasim
Date: 132023

University of Baghdad/ College of Medicine 2022-2023
Objectives:
▪ Define Measles, Rubella, and MMR vaccine.
▪ Explain the causative agent of Measles and Rubella diseases.
▪ Explain pathogenesis, diagnosis methods, control and treatment for
these viruses.

Measles:
• Is a highly contagious infectious disease caused by measles virus, and it
considered as an airborne disease which spread easily through cough
and sneeze of infected people.
• It may also be spread through direct contact with mouth or nasal secretion.
‫معدي‬
‫الحصبة‬

• Measles virus is a single stranded, negative sense , non segmented
enveloped RNA virus, of the genus Morbillivirus within the
family Paramyxoviridae.
• Measles is so contagious that if one person has it, 90% of nearby non-
immune people will also become infected. Human is the only natural host of
the virus, and no other animal reservoirs are known to exist.

Entry of the virus:
• The measles virus has two envelope glycoproteins the viral
surface hemagglutinin (H), and membrane fusion protein (F).
• These proteins are responsible for host cell binding and invasion.
Three receptors for the H protein have been identified to date:
complement regulatory molecule CD46 , the signaling lymphocyte
activation molecule (SLAM) and the cell adhesion molecule Nectin-4.
‫االن‬ ‫حتى‬

Genome replication and virus assembly:
• The negative sense strand of ssRNA is used to create a positive copy, then
this used to create a new negative copy, and so on, to create many copies of
the ssRNA.
• The ssRNA is then translated by host ribosomes, producing necessary
viral proteins. The viruses are then assembled, and the cell will lyse, leading
to restarting the cycle in a new cell.
‫تجمع‬

Symptoms of Measles:
• Symptoms typically begin two weeks after exposure, the classic symptoms
include a four days fever, cough, coryza, and conjunctivitis ,along with
a maculopapular rash.
• Fever is common and typically lasts for about one week; the fever seen
with measles is often as high as 40 °C.
• Koplik's spots seen inside the mouth are diagnostic for measles, but are
temporary and therefore rarely seen.
‫الزكام‬

• The characteristic measles rash is classically described as a
generalized red maculopapular rash that begins several days after the fever starts.
It starts on the back of the ears and, after a few hours, spreads to the head and neck
before spreading to cover most of the body, often causing itching.
• The rash is said to "stain", changing color from red to dark brown, before
disappearing.

Risk factors for measles virus infection:
▪ Loss of passive antibodies before the age of routine immunization.
▪ Travel to areas where measles commonly occurs or contact with travelers from
such an area.
▪ Corticosteroid therapy.
▪ Immunosuppression following receipt of an organ or a stem cell transplant.
▪ Immunodeficiency caused by HIV.
‫الجذعية‬ ‫الخاليا‬ ‫زرع‬ ‫أو‬ ‫العضو‬ ‫تلقي‬ ‫بعد‬ ‫املناعي‬ ‫التثبيط‬.

• Complications of measles are relatively common, ranging from mild ones such
as diarrhea to serious ones such as pneumonia, laryngotracheobronchitis, otitis
media, acute
• brain inflammation and corneal ulceration.
• In addition, measles can suppress the immune system for weeks to months, and
this can contribute to bacterial superinfections such as bacterial pneumonia.

• Measles can cause serious illness requiring hospitalization. One out of
every 1,000 measles cases progresses to acute encephalitis, which
often results in permanent brain damage.
• One to three out of every 1,000 children who become infected with
measles will die from respiratory and neurological complications.
‫للمستشفى‬ ‫الذهاب‬ ‫ببسبه‬ ‫يتطلب‬

Laboratory testing:
• Isolation & identification of virus:
• Measles virus grows slowly; typical cytopathic effects (multinucleated giant
cells containing both intranuclear and intracytoplasmic inclusion bodies)
• Laboratory diagnosis of measles can be done with confirmation of positive
measles IgM antibodies or detection of measles virus RNA from throat, nasal or
urine specimen by using the reverse transcription polymerase chain reaction
assay.

Treatment:
• There is no specific antiviral treatment if measles develops. Instead the
medications are generally aimed at treating superinfections, maintaining
good hydration with adequate fluids, and pain relief.
• Young children, are also given vitamin A, which act as an
immunomodulator that boosts the antibody responses to measles and
decreases the risk of serious complications
‫للمناعة‬ ‫معدل‬ ‫يعزز‬

• Treatment is supportive, with paracetamol to reduce fever and pain. using
of vitamin A during treatment is recommended to decrease the risk of
blindness; however, it does not prevent or cure the disease.
• A systematic review of trials into its use found no reduction in overall
mortality, but two doses (200 000 IU) of vitamin A was shown to reduce
mortality for measles in children younger than two years of age.

Rubella

▪ Rubella, also known as German measles is an infection caused by the rubella virus.
▪ Is an acute febrile illness characterized by a rash and lymphadenopathy that affects
children and young adults.
▪ It is the mildest of common viral exanthema.
▪ However, infection during early pregnancy may result in serious abnormalities of the fetus,
including congenital malformations and mental retardation.
▪ The consequences of rubella in utero are referred to as the congenital rubella syndrome.
Man is the only resvoir.
Only one antigenic type ‫فارييشن‬ ‫تسوي‬ ‫متكدر‬ ‫الن‬ ‫ثانية‬ ‫مرة‬ ‫متصير‬ ‫بعد‬ ‫مرة‬ ‫بيك‬ ‫صارت‬ ‫اذا‬ ‫لذلك‬.

Classification of the virus:
▪ Rubella virus, a member of the Togaviridae family, is the sole
member of the genus Rubivirus.
▪ Single-stranded RNA positive-sense, Enveloped. Three or four major
structural polypeptides.
‫الوحيد‬
It is the only human pathogenic virus in this genus

Structure of Rubella virus:
• The spherical virus particles have a diameter of 50 to 70 nm and are covered
by a lipid membrane, derived from the host cell membrane. There are
prominent projections composed of the viral envelope proteins E1 and E2
embedded in the membrane.
• The E1 glycoprotein is considered immunodominant in the humoral
response induced against the structural proteins and contains both
neutralizing and hemagglutinating determinants.

Replication of Rubella virus:
• The virus attach to the cell surface via specific receptors and are taken up by
an endosome. At the neutral pH outside of the cell the E2 envelope protein
covers the E1 protein.
• Dropping pH inside the endosome frees the outer domain of E1 and causes
the fusion of the viral envelope with the endosomal membrane. Thus, the
capsid reaches the cytosol, decays and releases the genome.
‫ويطلق‬ ‫يتحلل‬

• The positive, ssRNA at first only acts as a template for the translation of the
non-structural proteins, which are synthesized as a large polyprotein and are
then cut into single proteins.
• The sequences for the structural proteins are first replicated by the
viral RNA polymerase via a complementary (-) ssRNA as a template and
translated as a separate short mRNA. This short sub genomic RNA is
additionally packed in a virion.

• Translation of the structural proteins produces a large polypeptide.
This is then cut into E1, E2 and the capsid protein.
• E1 and E2 are transported into the endoplasmic reticulum with the
help of an N-terminal signal sequence.
• From the ER the heterodimeric (E1,E2-complex) reaches the Golgi
apparatus, where the budding of new virions occurs..

• The virus is transmitted by the respiratory route and replicates in
the nasopharynx and lymph nodes. The virus is found in the blood 5 to 7
days after infection and spreads throughout the body, and has the ability to
cross the placenta and infect the fetus.
• During the incubation period, the patient is contagious typically for about
one week before rash appearing and about one week thereafter.

Symptoms:
• The primary symptom of rubella virus infection is the appearance of a
rash on the face which spreads to the trunk and limbs. The facial rash
usually clears as it spreads to other parts of the body.
• Other symptoms include low grade fever, swollen glands which can
persist for up to a week and the fever rarely rises above 38 °C.

In older children and adults additional symptoms may be present including:
• Swollen glands coryza (cold-like symptoms)
• Aching joints (especially in young women)
• Severe complications of rubella include:
• Brain inflammation (encephalitis).
• Low platelet count.
• Ear infection.

• Rubella can cause congenital rubella syndrome in the newborn, this
syndrome follows intrauterine infection by the rubella virus and comprises
cardiac, cerebral, ophthalmic and auditory defects.
• It may also cause prematurity, low birth weight, and neonatal
thrombocytopenia, anemia and hepatitis. The risk of major defects
or organogenesis is highest for infection in the first trimester.

• Many mothers who contract rubella within the first critical trimester either
have a miscarriage or a stillborn baby. If the fetus survive, he may be born
with severe heart disorders , blindness, and deafness.
• The skin manifestations are called "blueberry muffin lesions". For these
reasons, rubella is included on the TORCH complex of perinatal infections.

Laboratory diagnosis of Rubella virus:
▪ Isolation & identification of virus:
o Nasopharyngeal or throat swabs taken 6 days before and after onset of
rash.
▪ Nucleic acid detection: RT-PCR.
▪ Serology:
o Detect specific IgM.
o Detection of IgG is evidence of immunity.

Treatment:
• There is no specific treatment for rubella; however, management is a matter
of responding to symptoms to diminish discomfort. Treatment of newborn
babies is focused on management of the complications. Congenital heart
defects can be corrected by direct surgery.
• Management for ocular congenital rubella syndrome is similar to that for
age-related macular degeneration, including counseling, regular monitoring,
and the provision of low vision devices, if required.

MMR vaccine:
• Is a vaccine against measles, mumps, and rubella. The first dose is generally
given to children around 9 to 15 months of age, second dose at 15 months to
6 years of age, with at least 4 weeks between the doses.
• The vaccine is also recommended in those who do not have evidence
of immunity, those with well controlled HIV, and within 72 hours of
exposure to measles among those who are incompletely immunized. It is
given by injection.

Thank you

ID2-MB-3-Paramyxoviruses.pdf

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