Micro - Opportunistic Viral Infections Flashcards
How are viruses classified
Baltimore classification, which classifies via the replicative life cycle and characteristics (dsDNA, ssDNA, RNA etc.)
Define opportunistic infections
An infection caused by an organism that does not normally cause disease in an immunocompetent host OR symptomatology may be altered in the immunocompromised compared to immunocompetent
What are endogenous opportunistic infections and give an example
Latent viruses that reactivate in the absence of a normal immune system
Acquired in the past prior to immune suppression
e.g. Varicella Zoster (VZV)
What are exogenous opportunistic infections and give an example
Viruses which are acquired from the environment
Increased severity in the immunocompromised
e.g. influenza, SARS-CoV-2
Give examples of AIDS defining illnesses and the viruses they are associated with
Cervical cancer – HPV
CMV
Encephalitis – HIV related
Chronic ulcers - HSV
Kaposi’s sarcoma – HHV-8
Lymphoma/Burkitt’s – infection of B-cell lymphocytes with EBV
PML – JC virus
What is the difference between indirect and direct detection of viruses
Indirect detection
- Useful to see whether you have ever had the infection
- Response of the immune system to the virus
Direct detection
- Useful to see whether you currently have the infection
- Viral proteins (lateral flow/antigen tests)
- Viral genetic material (virus genetic material is present with patient sample)
- Polymerase Chain Reaction, PCR
How is serology used for virus detection and what is the disadvantage of serology
Measure levels of antibody in patients serum
+++ IgM indicate Active or Resolving infection
+++ IgG indicates past infection > 6 weeks ago
BUT Antibody levels are reduced in Immunosuppressed (so this would not work in those with immunsuppression)
What are the advantages and disadvantages of PCR for virus detection
Detect viral genome in samples via amplification
Highly sensitive and specific
Performed on many different sample types
Viral load can be used to monitor infection
Tends to peak when most infectious
However, may remain positive after infection resolved
how are viruses screened for in those who are immunocompromised
- Screen prior to immunosuppression
- Identify previous viral exposure that may reactivate
- Can be done pre-transplant etc.
- Guide the use of antiviral prophylaxis
- E.g. HIV, HBV, HCV, EBV, CMV, HSV, VZV, HTLV - Monitor using PCR
- Identify viral reactivation promptly → Rx
- Detect infection
E.g. CMV, EBV, BK, Adenovirus, HSV
Which therapies carry a high risk of immunosuppression and therefore opportunistic infection (most likely first)
Allogeneic stem cell transplant
Advanced HIV infection
Solid organ transplant
Monoclonal antibody therapies
Cytotoxic chemotherapy
DMARDs and steroids
What is the difference in immunosuppression treatment for patients with a haematopoeitic stem cell transplant compared to those with a solid organ transplant
HSTC - Conditioning regimen - wiping out a disease completely (results in a very weakened immune system i.e. no neutrophils)
Ongoing immunosuppression as neutrophils start to be produced to prevent graft versus host prophylaxis → Can come off immunosuppresion
In a SOLID organ transplant - induction immunosuppression, rather than a conditioning regimen, is carried out to prevent rejection → Lifelong immunosuppression
How do you prevent infection in immunosuppressed patients who received a graft
Serostatus
Risk assessment
How do you prevent infection in immunosuppressed patients at risk of reactivation
Serostatus
Monitoring
Prophylaxis
Pre-emptive therapy
How do you prevent infection in immunosuppressed patients at risk of novel infection
Isolation-barrier nursing
Advice for family/contacts
Post-exposure prophylaxis
Vaccinating contacts
Control of diet
Which viruses are screened for in immunosuppressed patients who have a CNS infection
HSV
VZV
Enterovirus
EBV
CMV
Adenovirus
HHV6
JC virus
Which viruses are screened for in immunosuppressed patients who have a respiratory infection
Influenza A/B
Parainfluenza 1-4
Adenovirus
Enterovirus
RSV
HMPV
Rhinovirus
Coronavirus
CMV in BAL
Which viruses are screened for in immunosuppressed patients who have a haematological infection
CMV
EBV
Adenovirus
HHV6
Parvovirus