Transcript Rhinovirus - JUdoctors

Common
Cold
Faculty of Medicine
University Of Jordan
Common Cold
• Common Cold Syndrome is a general
term of acute inflammatory disease of
the upper respiratory tracts
• Syndrome includes rhinitis, tonsilitis,
pharyngitis, laryngitis pharyngolaryngitis etc.
• Sometimes Influenza (the flu) and
sinusitis are characterized as a common
cold syndrome.
Although many people are convinced
that a cold results from:
1. Exposure to cold weather
2. From getting chilled or overheated
3. Fatigue, or sleep deprivation.
These conditions have little or no effect
on the development or severity of a cold.
On the other hand, research
suggests that :
 Psychological stress
 Allergic disorders affecting the nasal
passages or throat
 Menstrual cycles
may have an impact on a person's
susceptibility to colds.
Common cold
 Acute respiratory infections, predominantly
rhinovirus infections, are estimated to cause
30-50% of time lost from work by adults and
60-80% of time lost from school by children.
 Up to 6 common colds/year in adults and 8
common colds/year for children acceptable.
 Medications can help relieve cold
symptoms, but only time can cure a cold.
Common Cold
 Common symptoms are sore throat, runny nose,
nasal congestion, sneezing,
 Sometimes accompanied by conjunctivitis, myalgias,
fatigue
 Sinusitis often present by CT scan; “rhinosinusitis”
might be a better term
 Seasonal variation
• Rhinovirus early fall
• Coronavirus- winter
Viruses Associated with Respiratory
Infection
Syndrome
Corza
Commonly Associated
viruses
Rhino and Picrona
Influenza
Influenza Virus
Croup
Parainfluenza
Bronchiolitis
RSV
Pronchopneumonia Parainfluenza, RSV,
Adenovirus
Less Commonly
Associated viruses
Influenza, Parainfluenza
Entero and Adeno
Parainfluenza, RSV,
Adenovirus
Influenza, RSV,
Adenovirus
Influenza, Parainfluenza,
Adenovirus
Parainfluenza, Measlse,
VZV, CMV
Common Cold Viruses
 Common colds account for one-third to one-half
of all acute respiratory infections in humans.
 Rhinoviruses are responsible for 30-50% of
common colds, coronaviruses 10-30%.
The rest are due to adenoviruses, enteroviruses,
RSV, influenza, and parainfluenza viruses,
which may cause symptoms indistinguishable to
those of rhinoviruses and coronaviruses.
Etiology
Common viruses that usually cause common
colds
 Rhinoviruses
 Parainfluenza or influenza viruses
 Respiratory Syncytial Virus (RSV)
 Coronaviruses
 Adenovirus
 Enteroviruses
Coxsackie Virus and ECHO Virus
 Reoviruses
Common Cold Viruses
Viruses
Serotype
 Rhinoviruses > 100
 Coronaviruses
2
 Influenza
3
 Parainfluenza
4
 RSV
2
 Adenovirus
47
 Entrovirus
>40
% C. cold
60
15
<10
<10
<10
<10
<10
Rhinovirus
 Rhinovirus infections are chiefly limited to the
upper respiratory tract but may include otitis
media and sinusitis.
 Rhinovirus plays a role in exacerbations of
asthma, cystic fibrosis, chronic bronchitis, and
serious lower respiratory tract illness in
infants, elderly persons, and patients who are
immunocompromised.
 Although infections occur year-round, the
greatest incidence is in the fall and spring.
 Of persons exposed to the virus, 70-80%
have symptomatic disease.
Rhinovirus
 Belong to the picornavirus family the smallest (pico) RNA
viruses (24-30 nm)
 ssRNA virus
 Acid-labile
 Rhinovirus Capsid consists of 4 proteins VP1, VP2, VP3& VP4
 At least 100 serotypes are known
 Intercellular Adhesion Protein-1 (ICAM-1)
 Receptor for most human rhinovirus serotypes
Rhinovirus bonded to
a CAM 1 receptor
Antibodies bonded
to a rhinovirus
Functions of Viral RNA
 RNA genome is mRNA Positive strand.
 A viral-coded peptide (VPg) is attached to the 5’ end.
 When introduced into cells, viral RNA can produce
infectious virus.
 Viral RNA serves as a template for its replication
 Optimum growth occurs between 33 and 34 oC
 Viruses replicate rapidly in the cytoplasm
 do not require DNA for reproduction
Functions of Viral Proteins
 Derived from one polyprotein precursor
 Processed by post-translational cleaving
 Structural proteins
• Responsible for host tropisms
• Protection of genome
• Antigenicity
 Non-structural proteins
• Proteases
• RNA polymerase
• Inhibitors of normal host cell functions
Virus Replication Cycle
Internal ribosome entry segment (IRES)
Coronavirus
 ssRNA Virus
 Enveloped,
pleomorphic
morphology
 2 serogroups:
OC43 and 229E
Transmission Routes
Cold viruses may be transmitted
by three routes:
 Large-particle droplets, which
can travel a short distance to
directly inoculate another
person
 Small-particle aerosols, which
can travel longer distances
and deposit
directly in alveoli of other individuals
 Secretion, which are transmitted by direct physical
contact
How does it spread?
 Very contagious
 Spread from person to person
 Usually from nasal secretions and from fingers
of the affected person
 Most contagious in the first 3 days after
symptoms begin
 Viruses can last up to 5 hours on the skin and
hard surfaces
Rhinovirus
Higher rates occur in humid,
crowded conditions, as found in
nurseries, day care centers, and
schools, especially during cooler
months in temperate regions and
rainy season in tropical regions.
Pathogenesis
 The offending virus invades the epithelial cells of
URT.
 Inflammatory mediators are released.
 They alter the vascular permeability and cause
tissue edema and stuffiness.
 Stimulation of cholinergic nerves in the nose and
URT leads to increased mucus production
(rhinorrhea) and occasionally to bronchocontriction
 Injury to cilia in the nasal epithelial cells may
decrease ciliary function and impair clearance of
nasal secretions.
Pathophysiology
• Rhinoviruses are transmitted to
susceptible individuals by :
 Direct contact
 Aerosol particles
infecting both ciliated areas of the nose and nonciliated
areas of the nasopharynx through receptors, most
frequently ICAM-1 (found in high quantities in the
posterior nasopharynx).
• Few cells are actually infected by the virus, and the
infection involves only a small portion of the epithelium.
Pathophysiology
• Symptoms develop 1-2 days after
viral infection, peaking 2-4 days
after inoculation, although reports
have described symptoms as early
as 2 hours after inoculation with
primary symptoms 8-16 hours
later.
Pathophysiology
 Detectable histopathology causing the
associated nasal obstruction, rhinorrhea, and
sneezing is lacking:
which leads to the hypothesis that the host immune
response plays a major role in rhinovirus pathogenesis.
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Infected cells release interleukin-8 (IL-8), which is a potent
polymorphonuclear (PMN) chemoattractant.
Concentrations of IL-8 in secretions correlate proportionally with
the severity of common cold symptoms.
Inflammatory mediators, such as kinins and prostaglandins, may
cause vasodilatation, increased vascular permeability, and exocrine
gland secretion.
These, together with local parasympathetic nerve-ending
stimulation, lead to cold symptoms
Pathophysiology
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Viral clearance is associated with the host response
and is due, in part, to the local production of nitric
oxide.
Serotype-specific neutralizing antibodies are found
7-21 days after infection in 80% of patients.
Although these antibodies persist for years, providing
long-lasting immunity, recovery from illness is more
likely related to cell-mediated immunity.
Persistent protection from repeat infection by that
serotype appears to be partially attributable to
immunoglobulin A (IgA) antibodies in nasal
secretions, serum immunoglobulin G (IgG), and,
possibly, serum immunoglobulin M (IgM).
Pathophysiology
• The virus has a limited temperature
range in which it can grow (33-35°C)
and cannot tolerate an acidic
environment.
Thus, finding the virus outside of the nasopharynx
is unlikely because of the acidic environment of
the stomach and the temperature elevation in both
the lower respiratory and gastrointestinal tracts.
The Common Cold
Chemical
Mediators
of Inflammation
VIRAL
INFECTION
OF NAZAL
CELLS
SNEEZING
SORE THROAT
Vascular
Dilatation
Increased
Vascular
Permeability
Tissue
Edema
Serum
Transduction
Increased
Mucus
Production
Sensitization
of Irritated of
Airways Receptors
NASAL OBSTRACTION
Cholinergic
Stimulation
RHINORRHEA
Bronchoconstriction
COUGH
Physical examination
• Red nose with dripping nasal discharge may
be present.
• Nasal mucous membranes have a
glistening, glassy appearance without
obvious erythema and edema.
• Yellow or green nasal discharge does not
indicate bacterial infection because a large
number of white blood cells migrate to the
site of viral infection.
Physical Examination
• If marked:
1. erythema, edema, exudates, or small
vesicles are observed in the oropharynx
2. conjunctivitis
3. polyps in the nasal mucosa occur, consider
other etiologies, including: adenovirus, herpes
simplex virus, mononucleosis, diphtheria,
Coxsackie A virus, or group A streptococcus
(GAS).
Clinical characteristics
 Incubation period 12-72 hours
 Nasal obstruction, drainage, sneezing,
scratchy throat
 Median duration 1 week but 25% can last 2
weeks
 Pharyngeal erythema is commoner with
adenovirus than with rhino or coronavirus
Symptoms
 Begins with a feeling of dryness and stuffiness in
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the nasopharynx (nose)
Nasal secretions (usually clear and watery)
Watery eyes
Red and swollen nasal mucous membranes
Headache
Generalized tiredness
If the pharynx and larynx
(throat) becomes involved:
Chills (in severe cases)
Sore throat
Hoarseness
Fever (in severe cases)
Exhaustion (in severe cases)
ICEBERG CONCEPT INFECTION
Sever Symptoms
Mild Symptoms
Infection but no Symptoms
Exposure but no Symptoms
Features Influenza
Common
cold
Onset
Abrupt
More gradual
Fever
Common
Uncommon
Myalgia
Severe ,
common
Severe ,
common
Common
Uncommon
Severe ,
common
Mild,
uncommon
Arthralgia
Anorexia
Headache
Uncommon
Uncommon
Cough (dry)
Common ,severe
Mild to moderate
Malaise
Severe
Mild
Fatigue,
weakness
More common
than with the
common cold ;
lasts 2 to 3 weeks
Very mild, short
lasting
Chest discomfort
Common ,severe
Mild to moderate
Stuffy nose
Occasional
Common
Sneezing
Occasional
Common
Sore throat
Occasional
Common
RISK FACTOR FOR MORE SEVER
COMMON COLD
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LOW NEUTRALIZING Ab
CHRONIC LUNG DISEASE
EXTREMES AGE
ASTHMA
• ALLERGY
• Ig E
• CYTOKINE PRODUCTION
 I F N -gamma
 I L-5
Complications
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Acute otitis media
Paranasal sinusitis
Neck lymphonoditis
Retropharyngeal abscess
Laryngitis
Lower respiratory tract disease
Acute glomerulonephritis and rheumatic fever
Laboratory Test
 White cell count
• The viral infections is normal to low.
• The bacterial infections or viral-bacterial
infection is high.
 Laboratory diagnosis of viral infections
• Antigen or nucleic acid detection
• Serologic testing
• Isolation of viruses by culture of the throat or
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nasopharynx
Use of monoclonal antibodies
Polymerase chain reaction (PCR)
TREATMENT
Treatment of common cold
 Antihistamines
 Decongestants
 Pain Relievers
 Cough suppressants
 Nasal Strips
 Antibiotics are ineffective!!!
MEDICATION
 Drugs used in the symptomatic treatment
include:
Nonsteroidal anti-inflammatory drugs
(NSAIDs)
 Antihistamines
 Anticholinergic nasal solutions
 These agents have no preventive activity
and appear to have no impact on
complications.
TREATMENT
• Rhinovirus infections are predominately mild
and self-limited:
thus, treatment is generally focused on symptomatic
relief and prevention of person-to-person spread and
complications.
The mainstays of therapy include:
• Rest,
• Hydration,
• Antihistamines,
• Nasal decongestants
• Antibacterial agents are not effective unless
bacterial superinfection occurs.
TREATMENT
 Development of effective antiviral medications
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has been hampered by the short course of
these infections.
Because peak symptom severity occurs at
24-36 hours after inoculation, only a narrow
window of time exists in which antivirals
could positively impact upon this infection.
In addition, the cause of the common cold is
not always rhinovirus.
Therefore, rapid and accurate diagnostic
tests would be needed if a specific antiviral
therapy were developed.
VACCINATION
Because of the large number of rhinovirus
immunotypes and the inaccessibility of
the conserved region of the viral capsid
(the most likely effective site for targeting a
vaccine), no rhinovirus vaccine is on
the horizon.
PREVENTION
• Because infection is spread by:
hand-to-hand contact,
autoinoculation,
possibly, aerosol particles,
emphasize appropriate hand washing,
avoidance of finger-to-eyes or finger-tonose contact, and use of nasal tissue.
Cough and sneeze into arm or tissue, not into
your hand
SUMMARY