Viral Respiratory Tract Infections Flashcards
What are the most common causes of the common cold?
Mostly rhinoviruses (80%) Some coronaviruses (15-20%)
Which infections does rhinovirus cause?
The common cold
COPD
Describe the coronavirus.
Large RNA virus
Found in animals and can jump species
Associated with severe infections, although are mostly mild
What is croup?
This is commonly encountered as a childhood infectious syndrome
Distinctive cough
Mostly mild but responsible for significant emergency visits (rapid onset with difficult breathing)
What normally causing croup?
Parainfluenza viruses 1-4
- normally occurs in the winter
- type three occurs in the spring
How is croup treated?
Supportive only (steroids) Not any curative treatment
What is the pathophysiology of Bronchiolitis?
Infection of the lower respiratory tract with the respiratory syncitial virus causes the bronchioles to become infected and inflamed. The inflammation reduces air entry into the lungs
Who are most commonly affected by bronchiolitis?
Babies and young children under the age of 2
- very common, most children are at least asymptomatically affected by the virus
What are the symptoms of bronchiolitis?
Fever
Dry and persistent cough
Difficulty feeding
Wheezing
What is the treatment for RSV (cause of bronchiolitis)?
Ribivirin (oral, IV or aerosolised) - benefit unclear - has many side effects, so only used in very severe infections Palivizumab - a prophylactic monoclonal antibody - give IM monthly - expensive
Name some symptoms of pneumonia.
High fever Headaches Cough with sputum Shortness of breath Pleuritic chest pain Fatigue Nausea
What is the most common cause of viral pneumonia?
Influenza virus
Describe the nucleic acid of an influenza virus.
RNA virus made up of eight different segments
What are the three forms of the influeza virus?
A -most dangerous type (forms neurominidase)
B - only circulates in humans
C- mild and untested for
What are the symptoms of influenza?
Fever
Muscle ache
Systemic features (headache, runny nose, cough, sore throat)
What is direct viral primary pneumonia?
Infection goes straight to the lungs and doesn’t cause any other side effects (just pneumonia symptoms)
What are the common complications of an influenza infection?
Acute otitis media Sinusitis Pneumonia Exacerbation of underlying diseases Dehydration (infants)
What are the uncommon complications of an influenza infection?
Encephalopathy Reye syndrome Myositis Myocarditis Febrile seizures
Which populations are most at risk of complications from an influenza infection?
Extremes of ages Chronic lung and heart disorders Immunosuppressed Pregnant Hepatic disorders
Describe the epidemiology of an influenza epidemic.
The kids are affected first because they all interact at school and infect each other
The parents of these children are then infected
Then adults in general are affected as they interact with each other
Why do influenza epidemics occur every year?
From one year to the next, the influenza virus mutates and changes in order to avoid our immune response (antigenic drift)
This means when the health board try and vaccinate people, they have to make educated guesses as to which mutations will have occurred in the past year
What is the treatment for influenza?
Neuroamidase inhibitors
- prevent release of the virus from the infected cell, stopping transmission
What is an influenza pandemic
A worldwide epidemic of a newly emerged strain of influenza
- few people are immune to the virus
- new virus can spread widely and easily and cause more serious illness
Describe the three ways in which antigenic shift can occur for the influenza virus.
1) Aquatic bird strain jumps straight to intermediate host then to humans without genetic change
2) Human or aquatic strain jumps to the intermediate host, where two viruses enter the same cell and reassortment occurs. Then the new strain is passed back to humans
3) Aquatic strain passes straight to humans without any genetic change
