RESP - Common cold, Influenza, Sinusitis, Pneumonia Flashcards
Common cold
Definition
Modes of transmission
Incubation period
Period of infectivity
General features
Acute self-limiting viral infection
One of upper respiratory tract infections (URTIs)
Usually last for 3 – 10 days in normal host but clinical illness may last up to 2 weeks
Modes of transmission
- Hand contact
* Direct contact via an infected person- Self-inoculation of one’s own conjunctiva or nasal mucosa after touching a person being contaminated with cold virus
* Indirect contact with a contaminated environmental surface
- Small particle droplet (Droplet transmission) from sneezing or coughing that remains airborne
- Large particle droplet (Droplet transmission) - Deposition of large particle droplets that are expelled during sneezing and land on nasal or conjunctival mucosa
Incubation period
- Most common cold virus = 24 – 72 hours
Period of infectivity
- Viral shedding peaks on third day after inoculation which coincides with peak in symptoms
- Low level of viral shedding may persist for up to 2 weeks
Common cold
Epidemiology
Etiology
Clinical sequalae
Seasonal patterns
* Rhinovirus infections in September (autumn months)
* Parainfluenza virus infection in October and November (autumn months)
* Coronavirus, influenza virus and respiratory syncytial virus infection in December to February (winter months)
Virolgy:
Immunity to virus
* Rhinovirus, influenza virus, adenovirus and enterovirus produce lasting immunity but immunity does little to prevent subsequent cold because there are too many serotypes
* Coronavirus, parainfluenza virus and respiratory syncytial virus does NOT even produce lasting immunity
Factors increasing susceptibility and severity of URTIs
* Underlying chronic illness
* Immunocompromised
* Malnutrition
* Smoking
Adenovirus infection
Specific complications
Clinical
- Respiratory infections = Pharyngitis/ Bronchiolitis/ Pneumonia
- Ocular infections = Conjunctivitis (self-limiting and requires no specific treatment) or Keratoconjunctivitis (more severe and sight-threatening form of adenovirus infection)
- GI infections = Gastroenteritis
- GU infections = Hemorrhagic cystitis (Presents with hematuria, dysuria, frequency and urgency but with negative urine bacterial culture results which resolves on its own within 1 – 2 weeks, Urinalysis shows RBC and sterile pyuria
Other complications include myocarditis, meningoencephalitis and hepatitis
Biochemical
- Leukocytosis with neutrophilia
Radiological
- Manifests as features more typical of bacterial disease including high fever, lobar infiltrates and parapneumonic effusions
Common cold
Pathogenesis
Common cold
Clinical presentation
Complications
Complications of common cold
Acute rhinosinusitis
Acute otitis media
Acute exacerbation of asthma
Lower respiratory tract disease (LRTI): Bronchitis, Acute bronchiolitis, Pneumonia
Common cold
URT and lRT infection S/S
Ddx Common cold
Physical examination
General examination
* Conjunctival injection
* Nasal mucosal swelling
* Nasal congestion
* Pharyngeal erythema
* Lymphadenopathy
Respiratory examination
* Usually unremarkable
Common cold
Ix
Tx
Ix:
- CXR NOT routinely indicated; Indicated is physical examination suggests signs of consolidation or other parenchymal disease
- Sinus X-ray: Indicated if suspect secondary sinusitis
- Nasopharyngeal aspirate/ Throat swab for culture: Cost-ineffective, impractical and unnecessary
Influenza
Clinical course
Types of influenza
Types of influenza virus
General features
Self-limiting and usually recovers in 2 – 7 days
Typical incubation period = 1 – 4 days
Transmission: Droplet transmission
Terminology
- Seasonal influenza (e.g. H1N1/ H3N2): Common respiratory tract infection caused by human seasonal influenza viruses; Circulate in human population and cause widespread illnesses during each influenza season
- Avian influenza (e.g. H5N1/ H7N9/ H9N2): Influenza viruses that mainly affect birds and poultry; infected through direct contact with infected birds and poultry, their droppings and contaminated environment
- Influenza pandemic (e.g. H1N1/ H2N2/ H3N2): Caused by emergence and global spread of a new influenza virus originated from an animal influenza virus such as avian influenza virus; Virus undergoes major genetic changes resulting in efficient human-to-human transmission
Types of influenza virus
- Influenza virus A: May lead to pandemics; Divided into 18H (H1 – 18) and 11N (N1 – 11) subtypes
- Influenza virus B: Do NOT lead to pandemics
- Influenza virus C: Do NOT lead to pandemics; Do not become ill with mild symptoms in general
Influenza virus
Epidemiology
Pathogenesis of new strains
Influenza virus
Clinical presentation
Influenza virus
Investigations
Influenza virus
Indications of treatment/ high risk patient groups
Nature of the disease
* Viral infection but not bacteria but therefore antibiotics has NO role
* Self-limiting disease with low morbidity and mortality
Treatment
* Treatment is mainly supportive including antipyretics to relieve discomfort, adequate hydration, respiratory support and treatment of complications
* Counselling on Tamiflu (see below)
* Advice on seasonal influenza vaccination
Influenza virus
Treatment options
Time course
Complications
Time course
- Antiviral is most likely to provide benefit when initiated within first 48 hours of illness
Indications:
- Individuals without higher risk conditions do NOT require testing or treatment; Individual present ≤ 48 hours can still be prescribed with antiviral to reduce the duration of illness by 1 day
- Individuals with high risk conditions or severe hospitalized (complicated) cases should receive antiviral treatment even > 48 hours after the onset of symptoms
Effectiveness
- Shorten duration of influenza symptoms by 1 day
- Reduce influenza complications
- Reduce duration of viral shedding
Dosing:
- For treatment = BD for 5 days (MUST complete full-course despite clinical improvement)
- For prevention = Once daily for 10 days
Adverse effects
- MOST common = Nausea and vomiting (15%)/ Headache
- MOST serious = Neuropsychiatric effects (Delirium/ Hallucinations/ Confusion/ Abnormal behaviors/ Convulsion/ Self-injury/ Suicidal ideation)
- Severe skin reactions (SJS/ Toxic epidermal necrolysis)
Influenza virus
Complications
Pneumonia (most common)
- Primary viral pneumonia: Bilateral reticular or reticulonodular opacities with or without superimposed consolidation on CXR
- Secondary bacterial pneumonia
Myositis and rhabdomyolysis
- Influenza B virus is well-known to cause acute myositis
- marked by muscle pain and weakness particularly in calf muscles and myoglobinuria
- ↑ Serum creatine phosphokinase (CK)
CNS infections
- Aseptic meningitis
- Encephalitis
- Reye’s syndrome: Rapidly progressive encephalopathy with hepatic dysfunction, characterized by vomiting and confusion which rapidly evolves into seizure and coma and hepatomegaly; associated with aspirin use
- Transverse myelitis
- Guillain-Barre syndrome (GBS)
Influenza virus
Vaccine type
High risk groups for vaccination
Contraindications to vaccination
Vaccine type:
- Only inactivated seasonal influenza vaccine is currently registered in HK
- Trivalent and quadrivalent inactivated influenza vaccines are recommended for use
- Requires about 2 weeks after vaccination for antibodies to develop and provide protection against influenza virus infection
Indications/ High priority groups
- Persons aged ≥ 50
- Children between age 6 months – 11 years
- Pregnant woman (only use inactivated seasonal vaccine, not live attentuated vaccines)
- Elderly living in residential care homes
- Long-stay residents of institutions for persons with disability
- Healthcare workers
- Poultry workers
- Pig farmers and pig-slaughtering industry personnel
- Chronic medical problems: CVS, Lung, Liver, Kidney, CNS, functional impairment and aspiration, immunocompromised states, children/ adolescent on long term aspirin therapy, prior pneumococcal diseases, prior cochlear implants, surgical history of CSF leak
Contraindications
- Allergy to previous dose of inactivated influenza vaccine or other vaccine components
- Allergy to egg if severe or history of anaphylaxis
Influenza virus
Drople precautions
Sinusitis
Definition
Classification
Sinusitis
Epidemiology
Sinusitis
Risk factors
Microbiology
Sinusitis
Anatomy of sinuses
Course, drainage, blood and nerve supply of each sinus
Sinusitis
Pathogenesis
Clinical features
Pathogenesis
1. Acute bacterial rhinosinusitis:
- Occurs most commonly as a complication of viral infection
- can also be associated with rhinitis or conditions that obstruct the nose or impair local or systemic immune function
- Acute viral rhinosinusitis
- Begins with viral inoculation via direct contact with conjunctiva or nasal mucosa
- Viral rhinitis spreads to paranasal sinus during nose blowing
- Inflammation occurs resulting in sinonasal hypersecretion and increased vascular permeability, mucosal edema, copious thickened secretions and impaired mucociliary clearance
Sinusitis
Diagnostic criteria
Ix
Diagnostic criteria
Acute bacterial rhinosinusitis
- Persistent symptoms or signs of ARS lasting ≥ 10 days without evidence of clinical improvement (OR)
- Onset of severe symptoms or signs of high fever and purulent nasal discharge or facial pain for at least 3 – 4 consecutive days at the beginning of illness (OR)
- Symptoms of a typical viral URTI that are slowly improving but worsen again with more severe symptoms and signs after 5 – 6 days
Acute viral rhinosinusitis
- Symptoms or signs of ARS < 10 days that are not worsening
Investigations:
- Anterior rhinoscopy
* Diffuse mucosal edema
* Narrowing of middle meatus
* Inferior turbinate hypertrophy
* Copious and purulent discharge
- Otoscopy
- Indicated in patients with symptoms of ear pain, fullness or pressure, hearing loss or tinnitus
- Biochemical tests: Sinus aspirate or endoscopic culture of middle meatus; indicated on suspicion of intracranial extension of infection or other serious complication
Imaging:
- X-ray sinus: sinus fluid levels, poor visualization of ethmoid sinuses
- CT sinus: air-fluid levels, mucosal edema and thickening, air bubbles within sinuses and opacification, e air-fluid levels, mucosal edema and thickening, air bubbles within sinuses and opacification
- MRI sinus: delineate extent of soft tissue involvement
Sinusitis
Treatment options
Medical:
- 1st line antibiotics: Augmentin/ Cefuroxime
- 2nd line antibiotics: Doxycycline/ Levofloxacin
- Glucocorticoids: Intranasal spray
- Analgesics: Paracetamol or NSAIDs
- Decongestants: For eustachian tube dysfunction
Surgical:
- Saline irrigation for pain relief
Sinusitis
Complications
Complications of acute rhinosinusitis
- Orbital and periorbital cellulitis
* Presents with ocular pain, eyelid swelling and erythema
* Orbital cellulitis will cause swelling and inflammation of extraocular muscles and fatty tissues within the orbit
* Leads to pain with eye movements, proptosis, ophthalmoplegia and diplopia
- Meningitis
- Brain abscess
- Epidural abscess
- Osteomyelitis of sinus bone: Presents with gradual onset of dull pain at involved site with or without movement
- Septic cavernous sinus thrombosis: Presents with cranial nerve palsies and headache
