Common Cold Faculty of Medicine University Of Jordan.

Common Cold

Faculty of MedicineUniversity Of Jordan

Common ColdCommon 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-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.

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. coldRhinoviruses > 100 60Coronaviruses 2 15Influenza 3 <10Parainfluenza 4 <10R S V 2 <10Adenovirus 47 <10Entrovirus >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 VirusEnveloped,

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 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.

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 Dilatation NASAL OBSTRACTION

Increased Vascular

Permeability

Tissue Edema

Serum Transduction

Increased Mucus

Production

Sensitization of Irritated of Airways Receptors

Cholinergic Stimulation

Bronchoconstriction

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. conjunctivitis3. 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 throatHoarseness

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

Uncommon

Arthralgia Severe, common

Uncommon

Anorexia Common Uncommon

Headache Severe, common

Mild, 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

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