Common Cold - JUdoctors · Common Cold •Common Cold Syndrome is a general term of acute...

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