Viral Infections of the Respiratory Tract

Question 1

List clinical terms to describe infections of the respiratory tract

Answer 1

Sinusitis, tonsillitis, otitis, epiglottis, tracheitis

Question 2

Distinguish between upper and lower respiratory tract infections

Answer 2

Upper respiratory tract infections: Common, normally viral but can be caused by secondary bacterial infection.
Lower respiratory tract infections: Less common, life threatening, e.g. pneumonia. LRT begins at the inferior border of the larynx

Question 3

Describe the common viral infections of the upper respiratory tract

Answer 3

Common cold (rhinitis), pharyngitis, tonsillitis

Question 4

Describe the features, and common aetiological agents, of infectious mononucleosis.

Answer 4

Infectious mononucleosis: Fever, malaise, lymphedema, sore throat, pharyngitis. Atypical mononuclear cells.
Infection of B cells by the virus
Aetiological agent: Viral: EBV Parasite: Toxoplasma

Question 5

List the common viral causes of LRTIs

Answer 5

• Influenza
• RSV (Respiratory Syncytial Virus)
  Rare: VZV, measles, SARS and MERS

Question 6

Describe the clinical features and epidemiology of influenza infection

Answer 6

Clinical features:
1.) Respiratory tract symptoms: Cough, rhinitis, shortness of breath
2.) Systemic symptoms: Fever, headache, myalgia
Epidemiology: Annual winter epidemics seen.

Question 7

List the mechanisms and describe the importance of antigenic drift and shift

Answer 7

Antigenic drift: Random mutations within the viral genome, 1% aa change. Mutations cluster in epitopes. Decreases the ability of the body to recognise the virus.
Antigenic shift: Only occurs in A. Viruses exchange gene segments. Leads to 20% aa change –> new subtype. Genetic assortment between human and animal viruses can lead to the emergence of new strains.

Question 8

Describe the clinical features and epidemiology of RSV infection

Answer 8

Clinical features: Causes LRTIs in infants (pneumonia, bronchiolitis). Has a high hospitalisation rate but low death rates - apart from when co-morbidities exist. Requires rapid diagnosis and infection control mechanisms. Reinfection occurs throughout life due to antigenic drift.
Epidemiology: High seasonal infection (winter), due to the ability of the virus to survive in the environment being increased (temperature and humidity).
Extremely common - everyone infected by age 2.

Question 9

Describe the features of the influenza virion

Answer 9

An enveloped virus
Surface neuraminidase (NA) and haemagglutinin (HA) molecules are seen.
RNA genome

Question 10

Outline the types, and subtypes, of the influenza virus

Answer 10

Types: A, B and C
Subtypes: Only type A virus has subtypes. These subtypes are defined on the basis of their NA and HA surface proteins.
For each subtype the genetic variability in sequence of these proteins is > 20 %

Question 11

Influenza infection symptoms

Answer 11

Respiratory: Rhinitis, cough, dyspnoea
Systemic: Fever, headache

Question 12

Influenza mounts what type of infection?

Answer 12

Lytic

PNEUMOTROPIC VIRUS

Question 13

Outline the complications of influenza infection

Answer 13

Pneumonia
Myocarditis
Encephalitis

Question 14

Which groups are at high risk of influenza infection

Answer 14

Pre-existing: Lung, cardiac, renal, endocrine, immunodeficiency and liver disease
> 65 years
Pregnant women
Children