�ݺ�ߣ

RNA Enveloped
Viruses
Dr Mohammed Salah 1
LECTURE IV
“Paramyxoviruses”

Enveloped RNA Containing Viruses
1. Orthomyxoviruses [segmented nucleic acid (7 - 8 segments)]
A. Human influenza A, B and C viruses.
B. Avian influenza virus.
C. Swine influenza virus.
2. Paramyxoviruses (non-segmented nucleic acid)
A. Human Para-influenza viruses (HPIV).
B. Mumps virus.
C. Measles virus.
D. Respiratory syncytial virus.

1. Nucleocapsid with helical symmetry.
2. Genome: (-) SS enveloped RNA
genome. Non-segmented; no shift or drift
(no antigenic variation).
3. Envelope: Outer surface with two surface
antigenic glycoproteins spikes;
a) Haemagglutinin-Neuraminidase (HN).
b) Fusion protein (F); mediates virus-
host cell membrane fusion.
 MORPHOLOGY

I. Human Para-influenza viruses (HPIV)
• The second most common cause of lower
respiratory infections (LRS) in infants and
young children.
• Cause 75% of cases of laryngeal obstruction
croup ‫الخناق‬
• However, HPIVs can also cause more severe
illness such as pneumonia.
• The incubation period of all the 4 serotype is
1-7 days
• There are 4 serotypes of HPIV.
 INTRODUCTION

Human Parainfluenza
virus type 1
HPIV-1 More frequent in the winter.
Most common cause of laryngeal obstruction (croup).
Human Parainfluenza
virus type 2
HPIV-2 Causes croup and other upper and lower respiratory tract
illnesses.
Human Parainfluenza
virus type 3
HPIV-3 Cause summer infection.
Associated with bronchiolitis and pneumonia.
Human Parainfluenza
virus type 4
HPIV-4 Includes subtypes 4a and 4b.
 SEROTYPES
 TRANSMISION
 The virus present in respiratory secretions so, infection is acquired
through droplet inhalation or contact with contaminated surfaces

 DISEASEANDCLINICALMANIFISTATIONS
 Human parainfluenza (influenza-like).
 Cause 30 - 40 % of all acute respiratory infections in infants
and children with;
• Mild, febrile common cold. ‫بحمي‬ ‫مصحوبة‬
• Severe laryngotracheobronchiolitis.
• Severe, life-threatening laryngeal obstruction (croup).
• Pneumonia (rarely).

1. Tissue culture:- Nasopharyngeal swab or aspirates and throat washings.
2. Serological:- Detection of specific antibodies using
immunofluorescent microscope and ELISA.
3. RT-PCR detection of viral specific nucleic acid.
Symptomatic treatment.
 DIAGNOSIS
 TREATMENT
 TREATMENT
 No available vaccine.
 Rapid diagnosis and strict isolation.

II. MUMPS VIRUS ‫النكاف‬
It is the cause of acute benign viral parotitis ‫النكاف‬, mumps,
(swelling of salivary glands) but the disease causes systemic
clinical symptoms.
Only one viral serotype exists.
Human are the only source of the virus.
« Inhalation through respiratory droplets »
« Incubation period 14-21 days »
 Introduction
 Transmission

Dr Mohammed Salah 9
 Pathogenesis

1. Non-purulent Swelling of one or both
of the parotid glands in front of the ear
and crossing into the corner of the jaw
2. Cough or runny nose
3. headache and muscle ache
4. tiredness
5. low-grade fever
6. abdominal pain and loss of appetite.
Dr Mohammed Salah 10
 Symptoms include:

1- Isolation of the virus from saliva, urine or CSF on monkey kidney cells.
2- serological testing (ELISA, haemagglutination inhibition):
 Detection of specific IgM antibodies in 1st serum sample (2-3 days) after onset
of rash
 four fold increase in antibody titer (IgG)
 detection of specific IgM.
• No specific antiviral agent
• Vaccination using the live attenuated mumps-measles-rubella (MMR) vaccine is
the only protective measure. Immunity is life long following infection or
vaccination. Given to children at 12 to 18 months of age.
 Laboratory diagnosis:
 Treatment and prevention:

III. MEASLES (RUBEOLA) ‫الحصبة‬
 Measles (Rubeola) is one of the most highly communicable acute
infectious diseases.
 Prior to widespread immunization 1988, measles was a common
childhood disease, with greater than 90% of infants and children
infected by 12 years.
 Only one viral serotype exists.
 Human and monkeys are the only
source of the virus.
 Causes viremia
 Target the skin and mucus membrane
 Introduction

1. Its transmission is by respiratory aerosol
2. by direct contact with nasal or throat secretions of infected persons.
Incubation period:- The incubation period varies from 7 to 18 days,
usually around 14 days.
 Transmission

 Highly contagious (communicable) disease.
 Measles typically begins with:-
1. high fever (may spike to more than 40°),
2. cough,
3. runny nose (coryza)
4. red, watery eyes (conjunctivitis) with red eyes
and white spots (Koplick spots) inside the
mouth.
5. Typical maculopapular rash (Exanthema)
appears after 1 - 3 days, starts behind the ears
and face and then spreads to the rest of the
body Dr Mohammed Salah 14
 Signs and symptoms

 Exanthema results from cell mediated immune
attack by cytotoxic T cells to the virus infected
vascular endothelial skin cells.
 The rash usually lasts 4 – 7 days but can persist
for up to 3 weeks
 Complications include:-
1. Otitis,
2. Blindness
3. Pneumonia,
4. Encephalitis
 Signs and symptoms

1. Measles is easy to be diagnosed clinically
2. Serological:-
1. Detection of IgM antibodies in 1st serum sample (2-3 days) after onset of rash or
2. 4-fold rising IgG antibodies 2nd serum sample (within 5-8 days).
3. Detection of viral specific RNA by RT-PCR.
1-There is no specific antiviral therapy for measles, and the basic treatment is supportive
therapy such as hydration and antipyretics.
2-Treating complications such as pneumonia.
3- Vitamin A supplementation improves outcome of measles.
• MMR vaccine is recommended whenever one or more of the individual components are
indicated. Immunity to measles is considered permanent.
 Diagnosis:
 Treatment:
 Prevention

IV. Respiratory Syncytial Virus
 Lacks the H and N antigenic glycoprotein.
 Size of nucleocapside less than paramyxovirus
 Causes fusion of cells together to form
syncytia
 Most common cause of severe lower
respiratory tract disease (bronchopneumonia)
in infants (< one year). In older children and
adults, the symptoms are much milder: it may
cause a coryza-like illness or bronchitis.
 Transmitted by:- Droplets infection
 Introduction

 Incubation period: 1 to 4 days.
 Following viral inhalation, it infects the respiratory
tract epithelium, causing cells death and sloughing.
 This lead to inflammatory response which
plug the bronchioles, cause bronchiolitis, and pneumonia.
 Obstruction of narrow airways may be fatal in infants.
 Viremia and secondary infection occurs.
 The virus causes syncytia that allow the virus to pass from
cell to cell directly.
 Pathogenesis

 Disease
 URT disease (Mild);
 Life-threatening LRT illness (bronchiolitis and pneumonia)
in infants and young children, among whom
this virus is the most important serious LRT pathogen.
 LRT illness in the elderly patients.
 Otitis media in young children; the virus
infect the middle ear directly or predispose
individuals to bacterial superinfection.
 Common cold symptoms in older children and adults.
 LRT disease;

Signs and symptoms
1. Runny nose, cough, fever, and wheezing.
2. Difficulty breathing.
3. Dusky color. ‫داكن‬ ‫لون‬

• Detection of specific antigen in nasal epithelial cells nasopharyngeal
secretions by; IFA & ELISA
• Tissue culture
• PCR
• Ribavirin aerosol in sever cases.
• Supportive with adequate oxygenation.
• Isolation and sanitation.
• Monoclonal antibody (MCA).
• Trials with killed vaccine.
 Laboratory Diagnosis:
 Treatment:
 Treatment:

RNA Enveloped
Viruses
LECTURE IV
“Toga viruses”

• Rubella virus is one of the Toga viruses,
• icosahedral enveloped viruses with positive sense SS RNA.
• (spike-like) contain haemagglutinin.
• Only one serotype exists.
• Humans are the only source.
Transmission
1. The disease is highly contagious, spread by nasal secretions (droplets).
2. Transplacental from mother to fetus.
• Rash appears after incubation period 14-25 days and unlike measles the symptoms
may be unapparent.
 Structure

Clinical Features and complications:
A. Postnatal rubella:
• In children, resemble measles in causing fever and skin rash but:
1. the disease is milder
2. with no Koplik`s spots and is self limiting of shorter duration (3
days),
3. and involving fewer complications.
• The rash generally first appears on the face and then spreads to the rest
of the body, and lasts about three days.
• Other symptoms that may occur 1 to 5 days before the rash appears
include:
1. a low-grade fever and headache
2. mild pink eye (redness or swelling of the white of the eye)
3. general discomfort
4. swollen and enlarged lymph nodes
5. Cough and runny nose

B. In adults
Most adults who get rubella usually have a mild illness,
1. with low-grade fever,
2. sore throat, and
3. a rash that starts on the face and spreads to the rest of
the body.
4. Some adults may also have a headache, pink eye, and
general discomfort before the rash appears.
5. About 25 to 50% of people infected with rubella will
not experience any symptoms

3. Congenital rubella:
Rubella infection is very serious in pregnant ladies as it crosses the placenta.
The virus affects differentiation but not proliferation of fetal cells and so it
is very dangerous during the first trimester of pregnancy only.
It results in congenital defects:
1. Splenomegally,
2. purpurea,
3. deafness,
4. blindness,
5. heart defects,
6. and mental retardness

By serological testing (ELISA, hemagglutination inhibition):-
four fold increase in antibody titer (IgG) or detection of specific IgM.
Treatment and control:
1- As there is no specific antiviral agent,
vaccination using the MMR (living attenuated mumps-measles-rubella) vaccine is the
only protective measure and should be given to girls before marriage.
2-Vaccination should be avoided during pregnancy and for 3 months before pregnancy.
Immunity is lifelong following infection or vaccination.
Laboratory diagnosis:

�ݺ�ߣ

AZU VIROLOGY LEC 4.pdf

More Related Content

AZU VIROLOGY LEC 4.pdf