Lecture 5: Aof pathogen 1: Viral colds Flashcards
How did the symptoms of runny nose and sore throat develop
Through inflammation of throat and nasal airspaces, causing redness, swelling, pain/irritation and sometimes purulence (yellow protein exudate)
What are the ways that we can catch viruses
Viruses have to make contact with the airways. It can transferred from human to human through
- aerosols/droplets
- direct contact (touching, cough, vertical, sexual transmission)
- indirect contact (touching contaminated surface, medical device, thru airborne particles, a vector,
How are viral colds diagnosed
Based on signs, symptoms and lack of other illnesses: must check for pneumonia and allergic rhinitis (hayfever). Lab tests are not helpful to diagnose common cold
What is the treatment and prevention for viral cold
They almost all get better on their own so treatment is to treat the symptoms using
- nasal decongestants, sedating antihistamines, non steroidal anti inflammatories for cough
Prevention is in hand hygiene and exercise
Compare the basic structure of enveloped and non enveloped viruses
Both have nucleic acid (RNA or DNA) and proteins/ enzymes in a protein capsid. Non enveloped present their surface viral proteins on this while enveloped present on the envelope = host cell membrane
What are the two classifications of viruses that are clinically relevant
Disease they cause or where they are transmitted
What are the 6 main steps of the viral life cycle
Binding, cell entry, uncoating the capsid or envelope, replicating proteins & nucleic acid, assembly of new virus particles, and exit.
Why does virus infection cause disease
- Through activating the immune system leading to excessive inflammatory response which can harm cells
- Damaging human cells directly by decreasing cell membrane integrity
What are 3 ways the immune system is alerted of the presence of virus
- Cytokines released by damaged cells as virus particles exit the cell
- Cells display viral surface proteins
- Cells withdraw self surface proteins (MHC-1) asking NK cells to kill them
What is viral tropism
Viral tropism refers to how some viruses create only specific diseases because they have viral proteins that only bind to specific molecules found on some human cells and not others.
Eg. HIV glycoprotein 120 binds specifically to CD4 receptors
What happens after the immune system is alerted of the presence of virus
- There is an increase in concentrations of systemic cytokines (eg IL6)nwhich build up locally and then leak into circulation, going on to interact with other cells/ tissues
- Further collateral damage to infected cells/ tissues
What are the symptomes related to cytokine release
fever, aches and pains, loss of appetite, lethargy, sense of illness/doom.
What virus is behind the cold, where does it infect and why, when do symptoms show and what is the duration of the cold
Rhinovirus- has more than 100 subtypes.
Infects the respiratory epithelial cells by binding to Icam1 or LDL receptor on the surface of cells and is confined to the airways.
The symptoms show after 1-3 days after contact, median duration is a week but can go to 2 weeks.
Compare the normal incidence of colds between children to adults
For children= 5-7/ year
Adults=1-2/year
What is healthcare associated infection
Infection related to healthcare. Onset can be in hospital (sick people bc of doctors) or in the community includes infections of healthcare workers.
