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 pharyngo-laryngitis 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 Commonly Associated Less Commonly
viruses Associated viruses
Corza Rhino and Picrona Influenza, Parainfluenza
Entero and Adeno
Influenza Influenza Virus Parainfluenza, RSV,
Adenovirus
Croup Parainfluenza Influenza, RSV,
Adenovirus
Bronchiolitis RSV Influenza, Parainfluenza,
Adenovirus
Pronchopneumonia Parainfluenza, RSV, Parainfluenza, Measlse,
Adenovirus VZV, CMV
Common Cold Viruses
Common colds account for one-third to one-halfof 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.
EtiologyCommon 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 % C. cold
Rhinoviruses > 100 60
Coronaviruses 2 15
Influenza 3 <10
Parainfluenza 4 <10
R S V 2 <10
Adenovirus 47 <10
Entrovirus >40 <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
Secretion, which are transmitted by direct physical contact
directly in alveoli of other individuals
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 particlesinfecting both ciliated areas of the nose and nonciliatedareas 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.
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• 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.
VIRAL
INFECTION
OF NAZAL
CELLS
SNEEZING
SORE THROAT
Chemical
Mediators
of Inflammation
Vascular
DilatationNASAL OBSTRACTION
Increased
Vascular
Permeability
Tissue
Edema
Serum
Transduction
Increased
Mucus
Production
Sensitization
of Irritated of
Airways Receptors
Cholinergic
StimulationBronchoconstriction
RHINORRHEA
COUGH
The Common Cold
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
the nasopharynx (nose)
Nasal secretions (usually clear and watery)
Watery eyes
Red and swollen nasal mucous membranes
Headache
Generalized tiredness
Chills (in severe cases)
Fever (in severe cases)
Exhaustion (in severe cases)
If the pharynx and larynx
(throat) becomes involved:Sore throat
Hoarseness
ICEBERG CONCEPT INFECTION
Sever Symptoms
Mild Symptoms
Infection but no Symptoms
Exposure but no Symptoms
Common
cold
Influenza Features
More gradual Abrupt Onset
Uncommon CommonFever
Uncommon Severe ,
common
Myalgia
Uncommon Severe ,
common
Arthralgia
Uncommon Common Anorexia
Mild,
uncommon
Severe ,
common
Headache
Mild to
moderate
Common ,severe Cough (dry)
Mild Severe Malaise
Very mild, short
lasting
More common
than with the
common cold ;
lasts 2 to 3 weeks
Fatigue,
weakness
Mild to
moderate
Common ,severe Chest discomfort
Common Occasional Stuffy nose
Common Occasional Sneezing
Common Occasional Sore throat
RISK FACTOR FOR MORE SEVER
COMMON COLD
LOW NEUTRALIZING Ab
CHRONIC LUNG DISEASE
EXTREMES AGE
ASTHMA
• ALLERGY
• Ig E
• CYTOKINE PRODUCTION
I F N -gamma
I L-5
Complications• 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 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
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-to-nose contact, and use of nasal tissue.
Cough and sneeze into arm or tissue, not into your hand
SUMMARY