Respi tract viruses Flashcards
Structure of influenza virus
Envelope
- lipoprotein
- covered w/ radially-projecting glycoprotein surface projections
Neuraminidase -> cleaves neuraminic acid receptors to allow virus release
Nucleocapsid
- type specific antigenicity -> influenza A,B,C
- RNA
Features of the radially-projecting glycoprotein surface projections
Haemagglutinin
Spikes for virus attachment to host cells -> specific for respi tract receptors
Antigenic variation
Clinical features of influenza
Incubation period -> 1-4 days
Abrupt onset of fever, myalgia, malaise, headache
Rhinorrhoea, sneezing
Sore throat, dry cough
Viral multiplication in respi epithelium w/ desquamation and ciliary damage
Complications of influenza virus infection
Pneumonia
- pri viral -> respi failure
- sec bacterial after damage of bronchial mucosa -> a lot of inflammation and excessive mucus production -> affect gaseous exchange
Myocarditis
Myositis
Reye’s syndrome
Common cause of sec bacterial pneumonia
S. pneumoniae
H. influenzae
S. aureus
Features of Reye’s syndrome
Usually associated w/ influenza B and aspirin intake in children
Cerebral oedema
Fatty degeneration -> liver
Lab diagnosis for influenza
Virus isolation
IF of antigen in respi epithelial cells
RT-PCR
Point-of-care (POC) test
Serology -> not commonly done
What are the various antigen structures of influenza?
Souluble/’s’ antigen
- same antigen shared by all influenza A viruses
Haemagglutinin
- varies from 1 strain to another
- main neutralising antigen responsible for host immunity
Why are there epidemics of influenza?
Due to antigenic variation
What is antigenic variation?
Recombination of RNA segments of 2 antigenic types simultaneously infecting same cell
Major antigenic change of both surface components
What is antigenic drift?
Spontaneous mutations leading to minor changes in haemagglutinin
Management of influenza virus infection
Differential diagnosis (flu-like illness)
Symptomatic treatment
Recognise and treat complications
Neuraminidase inhibitors -> -mivir
Polymerase inhibitors -> baloxavir
Minimise spread by respi route
Types of vaccination avail for influenza
Inactivated vaccine comprising of antigens from circulating A/H1N1, A/H3N2 and B strains
- quadrivalent -> cover B/Victoria and B/Yamagata lineages
Who are at risk of complications for influenza vaccine?
Elderly
Indivs w/ chronic cardiorespiratory conditions
Pregnant women
Issues w/ influenza vaccination
Timely preparation
Short-lived immunity -> strain of virus might have changed
Incomplete protection
Guillain-Barre syndrome
Features of paramyxovisruses
Enveloped helical RNA virus
No genetic recombination
Eg of pathogenic paramyxovisruses
Parainfluenza virus
Measles
Mumps
Clinical features of parainfluenza virus
Infection acquired by age of 5
4 serotypes
Disease associations w/ the various serotypes of parainfluenza virus
Type 1 -> croup in infants
Type 2 -> epidemics (winter)
Type 3 -> bronchiolitis and bronchopneumonia in young infants/croup in older infants
Type 4 -> minor respi infection
Common symptoms across the 4 serotypes of parainfluenza virus
Febrile common cold
- sore throat
- cough
- hoarseness
Croup
Bronchiolitis
Bronchopneumonia
Features of croup
Acute laryngo-tracheo-bronchitis
Cough, hoarseness
Severe -> dyspnoea, stridor, cyanosis
Lab diagnosis of parainfluenza virus infection
Tissue culture
Antigenic detection -> IF
RT-PCR
Serology
- early -> S antigen
- late -> V antigen
Treatment and control of parainfluenza virus infection
Ventilatory support
Antibiotics for sec bacterial infection
Sedation and hydration
Is there vaccine for parainfluenza virus?
No
Features of respiratory syncytial virus (RSV)
No haemagglutinin and neuraminidase
Commonest cause of bronchiolitis in young children
- wheezing is vry characteristic
Immune-mediated and/or mechanical obstruction of narrow bronchioles by inflammatory process
URTI in older children and adults due to larger bronchiole
Complications of RSV infection
Sec bacterial infections
Otitis media
Cardiac failure
Apnoea
Lab diagnosis of RSV infection
Tissue culture
Viral antigen demonstration -> IF
RT-PCR
Serology
- 1 serotype
Characteristic histological feature for RSV infection
Refractile syncytium (cells fusing) formation of multinucleated giant cells
Treatment and control of RSV infection
Ribavirin aerosol therapy
Ventilatory support
Isolation of infected
RSV monoclonal Ab to protect infants at risk of severe RSV disease
What are some things metapneumovirus associated w/?
Infants and children w/ acute respi disease
Asthma in children -> acute wheezing attacks
Symptoms of metapneumovirus infection
Similar to RSV infections
Features of adenovirus
DNA virus
More than 50 serotypes
Infect URT, mucosa and lymphoid tissue
Symptoms of adenovirus infection
Pharyngoconjunctival fever -> associated w/ swimming pool
URTI w/ fever
Pneumonia
Acute follicular conjunctivitis
Keratoconjunctivitis (shipyard eye)
Haemorrhagic cystitis
Enteritis
- mesenteric adenitis
- intussusception
Chronic infection of tonsils and adenoids
Lab diagnosis of adenovirus infection
Tissue culture
PCR
Serology -> IF/serotyping
Histological features of adenovirus infection
Swelling and clustering of infected cells w/ intra-nuclear inclusions -> bunch of grapes
Control of adenovirus infection
Vaccine (for certain serotypes)
Features of rhinovirus
More than 100 serotypes
Genetic/antigenic variation
Inhabit URT
Causative agent of common cold
May precipitate asthmatic attacks and aggravate chronic bronchitis
Readily spread by close contact and respi secretions
Neutralising Ab protective against same serotype -> can get common cold many times
Symptoms of rhinovirus infection
Rhinorrhoea
Sneezing
Sore throat
Cough
Mild fever
Hoarseness
Headache
NOTE: essentially symptoms of common cold
Lab diagnosis of rhinovirus infection
Tissue culture
Serotyping -> NT
RT-PCR
Features of coronavirus
Enveloped RNA virus
Crown-like projections on surface
Haemagglutinate RBCs
Multiple antigenic types
Cause common colds
Is tissue culture possible for coronaviruses?
No
Treatment and control of coronavirus
No specific treatment
No routine vaccines except for Covid-19
Eg of coronaviruses
SARS (severe acute respiratory syndrome)
MERS (middle east respiratory syndrome)
