Respiratory Tract Infections: Viral Infection Flashcards
What are host defences to protect against respiratory viruses?
Mucus
Cilia
Dendritic cells
Alveolar macrophages
What bacteria cause pharyngitis/ tonsillitis?
Streptococcus pyogenes
What viruses can cause pharyngitis/tonsillitis?
Adenovirus, rhinovirus, influenza, herpes simplex, HIV, EPB
What is an upper respiratory tract infection?
Infectious mononucleosis
Most commonly caused by Epstein Barr virus
Can also be caused by cytomegalovirus, HIV seroconversion and toxoplasmosis
What is lower respiratory tract?
Inflammation of the lower airways
Pneumonia is quite frequent
What are viral causes of lower respiratory tract infections?
Influenza
RSV
SARS-CoV-2
What are diagnostics for respiratory?
Laboratory testing e.g. nose/throat swab
Lateral flow
PCR
What are the four types of influenza virus?
A - infect humans and animals
B - seasonal epidemics
C - can infect humans and pigs but infections are generally mild
D - primarily affect cattle and are not known to infect or cause illness in people
Flu A and B are most circulating types
What is the genome in influenza?
In repeat segments - part of the orthomyxoviridae family
Why are you susceptible to re-infection by some acute viral infections?
Short lived immunity, become immunocompromised etc.
Immune escape mechanisms e.g. antigenic drift, antigenic shift, recombination
What is antigenic drift?
Error prone replication , more prominent in RNA viruses e.g. RSV and influenza A virus
What is antigenic shift?
Via reassortment, segmented viruses
What is influenza pathogenesis?
Viral replication in epithelial cells
Multi focal destruction and desquamation of epithelium of trachea and bronchi
Recruitment of pro-inflammatory neutrophils and macrophages
Air spaces fill with oedema, blood
What is prevention of influenza?
Live attenuated seasonal influenza vaccine (children)
Inactivated seasonal influenza vaccine (adults)
What is treatment for influenza?
Neurominidase inhibitors - prevents release of influenza virion from host cell (oseltamivir, zanamivir)
Cap-dependent endonuclease inhibitor - inhibits viral replication (baloxavir)
What is RSV virology?
Enveloped -ve ssRNA
3 surface glycoproteins (small hydrophobic (SH), fusion (f), attachment (G))
What is RSV pathogenesis?
Attachment to host cell via receptors (e.g. CX3CR1)
Fusion with cell membrane
Viral entry
Syncytia formation
Viral replication
Spread to lower respiratory tract
Cell death, epithelial necrosis
What is RSV clinical presentation in children?
Bronchiolotis
Short history cough, low grade fever, difficulty breathing
What is RSV clinical presentation in adults?
URTI, viral-induced wheeze, acute exacerbation of asthma, pneumonitis
What are risk factors of RSV?
Extremes of age
Congenital heart/lung disease
Infants born with low material antibody titre
Immunodeficiency
Exposure to smoke/air pollution
What is prevention of RSV?
Palivizumab - monoclonal antibody
Nirsevimab - monoclonal antibody
RSV vaccine - mRNA and protein vaccines
What is treatment for RSV?
Ribavirin - guanosine analogue which inhibits viral genome replication
IVIG - limited evidence for efficacy, except when given in combination with ribavirin for immunosuppresed patients
What type of coronavirus is SARS-CoV-2
Beta coronavirus
What jobs does spike attachment protein do?
Both the jobs of attachment and fusion
What type of genome does SARS-CoV-2 have?
Enveloped, +ve ssRNA genome
What is the receptor for SARS-CoV-2?
Angiotensin converting enzyme 2
When are anti virals most useful?
Early infection when the virus is replicating
What is prevention of SARS-CoV-2?
SARS-CoV-2 vaccine
What are treatments for SARS-CoV-2?
Antivirals
Anti-inflammatory es
Supportive care - anti-coagulation and antibiotics
