Level 2 - Infections Flashcards
Definition of chicken pox?
- Highly infectious disease caused by herpes virus transmitted by air droplets
- VZV infection between 1-6yrs commonly —winter/spring
- Varicella is very infectious
Transmission of chicken pox? Infectious period?
- Transmission is by personal contact or droplet spread, with an incubation period (the time from becoming infected until symptoms appear) of 1-3 weeks
- Chickenpox is infectious from 1-2 days before the rash appears until the vesicles are dry or have crusted over, usually 5 days after the onset of the rash
What is Herpes Zoster?
- Herpes Zoster (shingles)
o a reactivation of the latent infection may occur -> vesicular lesions in the distribution of the sensory nerve. Increased risk in immunosuppressed
Epidemiology of chicken pox?
- Incidence is highest before 10 years of age
- > 90% of people older than 15 years of age UK are immune
- Peak incidence from March-May
Causes of chicken pox? Name a risk factor?
- Caused by varicella-zoster virus (VZV)
- Immunocompromised
Prodrome of chicken pox?
- Infection begins 2 days before vesicles appear
- Infection ends when last vesicle crusts over
Rash in chicken pox?
- Head and trunk rest of body.
- Red macules papulevesiclepustulecrusting
- Completely heal in 2wks
Other symptoms in chicken pox?
headache, anorexia, URTI (sore throat, coryza, cough), fever and itching
Investigations (when needed) for chicken pox?
Ex: Characteristic rash, its distribution and progression
Other: Serology (VZV IgM), vesicle fluid or electron microscopy
Management of chicken pox?
Usually self-limiting, symptomatic: Paracetamol, calamine lotion and chlorphenamine
School exclusion: 5 days from start of skin eruption
Antivirals: Acyclovir if severe, in babies and immunosuppressed
Human varicella zoster Ig recommended for high risk immunocompromised
Complications of chicken pox in pregnancy?
- Varicella in pregnancy can result in severe chickenpox
- Infection during 1st 28 weeks of pregnancy can lead to intrauterine infection and foetal varicella syndrome
Other complications in chicken pox?
- Secondary bacterial infection
o Due to staphylococcal/streptococcal leading to toxic shock syndrome or necrotising fasciitis - Encephalitis
o Cerebellitis, meningitis - Purpura fulminans
o Vasculitis in the skin due to cross-reactivity of antiviral antibodies - Immunocompromised can disseminate causing pneumonitis/DIC – fatal 20%
Define conjunctivitis? Classification?
- Redness and inflammation of conjunctiva (thin layer that covers front of eye)
- Hyperaemic vessels may be moved to sclera by pressure on globe
- Classified as infectious or non-infectious, and as acute (<4 weeks), chronic, or recurrent
What is allergic conjunctivitis?
o Associated with IgE antibodies or non-atopic
o Can be acute/chronic or seasonal (hayfever)
What is infectious conjunctivitis?
o Hyper-acute conjunctivitis is a rapidly developing severe conjunctivitis typically caused by infection with chlamydia
o Ophthalmia neonatorum (ON) is conjunctivitis occurring within the first four weeks of life
Can be infectious or non-infectious
Can be caused by Chlamydia trachomatis or Neisseria gonorrhoeae
Epidemiology of allergic conjunctivitis?
o 15-40% of children
Infectious aetiologies of conjunctivitis?
o Viral
Most common 80% adenoviruses
HSV, VZV, EBV, Coxsackie
o Bacterial
Streptococcus pneumoniae, Staphylococcus aureus and Haemophilus influenzae
Moraxella catarrhalis, Chlamydia trachomatis, and Neisseria gonorrhoea
Non-infectious causes of conunctivitis?
o Allergic, mechanical/irritative/toxic, immune-mediated and neoplastic
Symptoms of conjunctivitis?
- Eyes itch, burn, ‘gritty feeling’ and lacrimate
- Often bilateral with discharge sticking lids together
Explain different discharges in conjunctivitis?
- Discharge can be watery, mucoid, purulent depending on cause
o Bacterial purulent with sticking lids, may have lymphadenopathy
o Viral watery discharge and less, URTI
What happens to eye function?
- Acuity, pupillary responses, corneal lustre are unaffected
DDx of conjunctivitis?
- Acute glaucoma, Scleritis, Episcleritis, Keratitis, Uvitis, Iritis, Corneal ulcer, abrasion or foreign body
- Nasolacrimal duct obstruction
- Dry Eye
- Blepharitis
Investigations of conjunctivitis?
- Slit lamp examination if needed
- Gram staining and culture if gonococcal suspected
When is sticky eyes common? Management?
- Sticky eyes common in first few days of life
o Clean with saline
o Eye drops lubricating
Management of conjunctivitis? Bacterial?
Allergic?
Neonates?
Opthalmia neonatorum?
- Usually self-limiting and rarely causes loss of vision (resolves within 5-10 days)
- Bacterial Conjunctivitis
o Chloramphenicol topical drops (or fusidic acid drops) - Allergic Conjunctivitis
o Topical antihistamines
o Topical corticosteroids
o Cromoglycate eye drops - Neonates
o Treat with neomycin - Ophthalmia Neonatorum
o Gonococcal infection should be cultured and treated with 3rd generation cephalosporin given
o If chlamydia infection then treated with oral erythromycin
Complications of conjunctivitis?
- Keratoconjunctivitis
- Keratitis
- ON
o Corneal scarring, ulceration, visual impairment
What is a food allergy? Type of reactions?
- Immediate IgE-antibody allergic reaction to specific food antigens
- 70% have FHx of atopy
- Immunological reactions - both IgE (acute, often rapid, onset) and non-IgE-mediated (delayed and non-acute reactions)
- Food Intolerance – non-immunological hypersensitivity to specific food