14. Respiratory Viruses Flashcards
How are respiratory viruses transmitted?
Droplets and fomites
Which bacteria are transmitted via droplet spread?
Pertussis
Neisseria meningitidis
Group A strep
Which viruses cause the common cold?
Coronavirus
Rhinovirus
Adenovirus
How are influenza viruses classified?
Based on their core proteins
A, B and C
What are the reservoirs of influenza viruses A, B and C?
A: Birds and mammals
B and C: confined to humans
Which influenza virus is most commonly associated with outbreaks and epidermics?
A causes an epidemic seasonally
B causes one every 2-4 years
C is uncommon and associated with a milder disease
What dictates the subtype of an influenza virus?
Haemaglutinin and neuraminidase
What is antigenic drift?
Minor antigenic change due to errors in viral DNA polymerase
Results in yearly epidemics as population only has limited immunity
What is antigenic shift?
Major antigenic change caused by genes being swapped from different strains
What is the function of haemaglutinin?
Binds to receptors on host respiratory epithelial cells
What is the function of neuraminidase?
Cleaves sialic acid in respiratory epithelium
Allows release of virus from the cell and prevents clumping
How can an influenza infection cause a bacterial superinfection?
Inflammation of the trachea and bronchi leads to ulcerative necrotising trachea-bronchitis and loss of cilia
What are the clinical features of influenza?
Abrupt onset of a fever, cough and myalgia
Persistent weakness and depression
What time frame is someone infectious with influenza?
1-2 days before symptoms to 7 days after
What percentage of people are asymptomatic with influenza?
30%
What complications are associated with influenza?
Pneumonia
Secondary bacterial superinfection
Myositis/mycarditis
Reye’s syndrome
What pathogens can cause bacterial superinfection after influenza?
Strep pneumoniae
H. influenzae
Staph aureus
What is Reye’s syndrome?
Encephalopathy and liver failure after giving aspirin to children with a fever
What is the treatment for influenza?
Supportive: analgesics, antipyretics
O2 if hospitalised
NA inhibitor antivirals
Who should be vaccinated against influenza?
Anyone at high risk
Healthcare workers
All children 2-12
What long term drug puts someone at higher risk for influenza?
Aspirin
You can be reinfected with RSV. T/F?
True
What part of the respiratory system does RSV damage?
Bronchioles
What are the signs of RSV?
Respiratory distress: tachypnoea, nasal flare, wheeze Apnoea Irritability Cyanosis Prominent intercostal retraction
What does intercostal retraction suggest?
Lower airway obstruction
What is seen on a CXR in an RSV infection?
Flattened diaphragm and hyperlucent lower lung (hyperinflation)
What immunity is given to those at high risk of RSV?
Palivizumab: passive immunity
How many parainfluenza serotypes exist?
4
What is the incubation time of parainfluenza?
3-6 days
What diseases are caused by parainfluenza?
Croup
Bronchiolitis
How are parainfluenza, RSV and influenza detected?
Multiplex PCR
How many serotypes of adenovirus exist?
> 50
What diseases are caused by adenovirus?
Wide range of RTIs
Diarrhoea
Conjunctivitis
What samples can be taken if a patient is suspected of having a respiratory virus?
Nasopharyngeal aspirates
Throat swabs
BAL
Sputum
Name 3 recent epidemics
Avian influenza
SARS
MERS-COV
What animal served as a mixing vessel in avian influenza?
Pigs
What animals were the reservoir hosts in MERS-COV?
Camels and bats
What is the incubation period of COVID-19?
1-14 days
Median 5-6
What are the common presentation of COVID-19?
Fever
Cough
SOB
Lack of smell and taste
What are other symptoms of COVID-19?
Myalgia Headache Sore throat Nasal congestion Vomiting Diarrhoea Fatigue
Which patient groups are more likely to have less typical symptoms?
Elderly
Immunosuppressed
What are the complications of COVID-19?
ARDS
Thromboembolism
Sepsis
What are the risk factors for severe COVID-19?
> 60
Underlying diseases
Smoking
How is COVID-19 diagnosed?
Nasopharyngeal and throat swab
RT-PCR for viral RNA (because SARS-COV-2 is an RNA virus, DNA must first be made to use PCR)
What genes does RT-PCR look for in COVID?
E gene
N gene
RNA polymerase genes
What cardiac sequelae may follow COVID?
Arrhythmias
Myocardial injury
Postviral myocarditis
What factors might cause cardiac sequelae after COVID?
Virus itself Hypoxia ACE2 receptor downregulation Hypotension Inflammation Drug toxicity
Who is at risk of acute kidney injury due to COVID?
elderly male CV disease Hypertension Chronic kidney disease
How is ‘long COVID’ defined?
Symptoms longer than 3 weeks after first onset of symptoms
Define chronic COVID?
> 12 weeks after onset of symptoms
What symptoms are associated with long/chronic COVID?
Ongoing cough, fever, fatigue, SOB
Psychiatric, cognitive and physical impairments
