Viral infections Flashcards
(28 cards)
How do the levels of IgG and IgM differ in primary and secondary response to viral infection?
=> Primary exposure
IgM rises before IgG
=> Secondary exposure
- Both rise at same time
- Greater rise in IgG compared to IgM
What are the general steps of viral replication/infection?
- Virus binds to receptor on host cell
- Endocytosis
- Un-coating
- Reverse transcriptase action to form viral DNA
- Viral DNA enters nucleus
- Integration into host DNA
- Transcription + Translocation
- Viral proteins assembled
- Released
What are the principles of anti-viral therapy?
- Viral replication is recognised by Pattern Recognition Receptors (PRRs) on the surface of immune cells
- These receptors trigger the innate immune response to produce restriction factors such as Type 1 Interferons
=> Antiviral therapy either stimulates these PRRs or boosts the immune response through exogenous Type 1 Interferons
What are the 2 different subtypes of the Herpes Simplex Virus?
HSV 1 => oral lesions
HSV 2 => genital herpes
There may be considerable overlap
What is Herpes Labialis?
- Cold sores which tend to be caused by HSV-1
- Spread via direct contact with the lesion
- Primary infection is frequently asymptomatic
What is the clinical presentation of Herpes Labialis?
- Pharyngitis
- Fever
- Mouth ulceration
- Lymphadenoapthy
- Localised painful blisters that resolve in 5-7 days
What is the management of Herpes Labialis?
Topical Aciclovir
What is Herpes Genitalis?
- Genital herpes caused by HSV-2
What is the clinical presentation of Herpes Genitalis?
- Painful genital ulceration
- Fever
- Lymphadenoapthy
- Urinary retention
What is the management of Herpes genitalis?
PO Aciclovir. Some people with frequent exacerbations may benefit from long term Aciclovir
What is Herpes Simplex Encephalitis?
- Severe life threatening infection of the CNS
- Typically affects the temporal and frontal lobes of the brain
- Virus spreads in the body via neurones
What is the clinical presentation of Herpes Simplex Encephalitis?
- Fever, headache, psychiatric symptoms, seizures, vomiting
- Aphasia
What is the pathophysiology of Herpes Simplex Encephalitis?
- HSV-1
- Typically affects medial temporal or inferior frontal lobes
What are the investigations in suspected Herpes Simplex Encephalitis?
=> CSF
- Lymphocytosis
- Elevated proteins
=> Imaging
- CT - typically performed first to exclude raised ICP (contraindicates CSF analysis)
- MRI is better
=> EEG
What is the management of Herpes Simplex Encephalitis?
IV Aciclovir
What is chicken pox (varicella) and its investigations?
- Caused by primary infection with Varicella Zoster Virus
- Spread via respiratory route
- Latent reactivation results in shingles
- Infective 4 days before rash till 5 days after rash onset when all lesions crusted over
=> Diagnosis:
- Clinical diagnosis made
- If immunocompromised: viral PCR, culture, immunofluorescence
What is the management of Varicella infection?
PO Aciclovir
This medication is most effective in this order:
- HSV 1
- HSV 2
- VZV
Aciclovir resistant herpes is treated with Foscarnet or Cidofovir
What categories of patients should always be treated with antiviral therapy in cases of infection?
- Immunocompromised
- Pneumonitis
- Encephalitis
- Eye disease
What is Cytomegalovirus (CMV) and its diagnosis?
One of the herpes viruses
- Usually affects foetuses or the immunocompromised
=> Diagnosis:
- Quantitative nucleic acid amplification testing
What are the complications of CMV in the immuncompromised?
- CMV mononucleosis
- CMV encephalitis
- CMV colitis
- CMV retinitis
- CMV pneumonitis
What clinical syndromes come und the Human Herpesvirus?
=> HSV:
- Herpes Labialis (HSV-1)
- Herpes Genitalis (HSV-2)
- Herpes Encephalitis (HSV-1)
- Herpes Gingivostomatitis (primary HSV-1 cold sore infection)
- Herpes Keratoconjunctivitis
- Herpetic Whitlow
=> Others
- Varicella Zoster Virus (HHV 3)
- EBV (HHV 4)
- CMV (HHV 5)
- Human Herpesvirus 6
- Human Herpesvirus 8
What is the Epstein Barr Virus (EBV) and its diagnosis?
- Also known as HHV-4
- Most common cause of infectious mononucleosis (grandular fever)
- Salivary transmission
=> Diagnosis:
- Blood film showing lymphocytosis
- Heterophile antibody tests - 1st line
- IgM serology
- Reverse transcriptase viral PCR
=> Hetrophile Antibody test (Monospot) and FBC should be done in 2 weeks to confirm the diagnosis of grandular fever)
What are the clinical features of EBV infection?
=> Classic triad: sore throat, fever, lymphadenoapthy
- Splenomegaly
- Headache
- Malaise
- Macular rash (can develop in people who take amoxicilin) and Palatal Petechiae
What is the management of CMV and EBV?
For EBV, rest, avoid alcohol and simple analgesia for any aches and pains. Avoid all contact sports for 8 weeks to reduce risk of splenic rupture
- Aciclovir not effective
- First line treatment - Ganciclovir and Vanganclicovir
- Second like treatment - Forcarnet or Cidofovir
