Infections Flashcards
C - Herpes Simplex Virus 1
- an intensely painful infective ulcer on the fingertips is herpetic whitlow
- tingling sensation tends to precede herpes
- this is common in dentists as they are in contact with a lot of mouths
D - paracetamol & Calamine lotion
- treatment for chickenpox in children is aimed at symptomatic relief
- in adults, treatment is aimed at eradicating the virus
- oral acyclovir is given in adults
- oral valaciclovir is the treatment for shingles
B - this rash can only present unilaterally
- this is shingles, which has a dermatomal distribution
- it is caused by reactivation of VZV
- there is tingling in a dermatomal distribution
- treatment is with valaciclovir
- it is caused by a DNA virus
EBV
- it is NOT streptococcus pyogenes as strep throat presents with anterior cervical lymphadenopathy
- EBV presents with posterior cervical lymphadenopathy
E - Human herpesvirus 8
- this man has HIV, which predisposes him to Kaposi’s sarcoma
- this is caused by HHV8
What is the name of HHV-1?
How is it transmitted and what is the clinical presentation?
herpes simplex virus - 1 (HSV-1)
Transmission route:
- respiratory droplets / saliva
Clinical presentation:
- gingivostomatitis (mouth or gum swelling)
- keratoconjunctivitis (inflammation of cornea & conjunctiva)
- herpes labialis (cold sores)
- temporal lobe encephalitis
What is the name of HHV-2?
How is it transmitted and what is the clinical presentation?
herpes simplex virus 2 (HSV-2)
Transmission route:
- sexual contact
- perinatal
Clinical presentation:
- genital herpes
- neonatal herpes
What is the name of HHV-3?
How is it transmitted and what is the clinical presentation?
varicella zoster virus (VZV)
Transmission route:
- respiratory
Clinical presentation:
- chicken pox
- shingles
What is the name of HHV-4?
How is it transmitted and what is the clinical presentation?
Epstein-Barr virus (EBV)
Transmission route:
- saliva - known as the “kissing disease”
Clinical presentation:
- mononucleosis - associated with lymphomas & nasopharyngeal carcinoma
What is the name of HHV-5?
How is it transmitted and what is the clinical presentation?
cytomegalovirus (CMV)
Transmission route:
- congenital
- sexual
- saliva
Clinical presentation:
- mononucleosis in immunocompromised patients
What is the name of HHV-6 and HHV-7?
How is it transmitted and what is the clinical presentation?
HHV-6 & HHV-7
Transmission route:
- saliva
Clinical presentation:
- roseola infantum (high fever followed by a rash in infants)
What is the name of HHV-8?
How is it transmitted and what is the clinical presentation?
HHV-8
Transmission route:
- sexual contact
Clinical presentation:
- Kaposi’s sarcoma
What is the definition of herpes simplex virus?
How common is it?
this describes disease resulting from HSV1 or HSV2 infection
it is very common with 90% of adults seropositive for HSV1 by 30 years
it can be asymptomatic
What is the presentation of HSV-1 like?
herpes virus - think VESICULAR rash
- gingivostomatitis, cold sores (herpes labialis)
-
herpetic whitlow
- painful vesicular lesions on the hands / fingers
-
eczema herpeticum
- looks like eczema, but rash is vesicular
- herpes simplex meningitis, encephalitis
- systemic infection
- keratoconjunctivitis
What is the presentation of HSV2 like?
this presents as genital herpes, which is chronic and life-long
- flu-like prodrome
- vesicles / papules around the genitals & anus
- shallow ulcers
- urethral discharge
- dysuria
- fever and malaise
What is the aetiology for herpes simplex virus?
- the virus becomes dormant following primary infection
- it travels to the trigeminal / sacral root ganglia and stays there
- reactivation may occur in response to stress or immunosuppression (HIV)
What are the 2 phases involved in herpes simplex virus infection?
Latent phase:
- chronic infection where infectious virions are not produced
- the virus is within the trigeminal/sacral root ganglion
- there are no symptoms
Lytic phase:
- there is viral replication and transport of the virus to the skin
- this is active infection that produces symptoms
What investigations are carried out for herpes simplex virus?
What is involved in the management?
Investigations:
- usually a clinical diagnosis
- may consider viral culture / HSV PCR (not usually done)
Management:
- topical, oral or IV acyclovir depending on severity of presentation
What is the definition of varicella zoster infection?
- the primary infection is varicella (chickenpox)
- reactivation of the dormant virus in the dorsal root ganglia causes zoster (shingles)
this usually occurs due to stress and presents in a dermatomal distribution
What is the epidemiology of varicella zoster virus like?
- chickenpox has a peak incidence between 4 to 10 years
- shingles has a peak inidence of > 50 years
- around 90% of adults are VZV IgG positive
What is the presentation of chickenpox like?
- prodromal malaise
- mild pyrexia
- generalised pruritic vesicular rash
- this predominantly affects the face and trunk
- contagious from 48 hours before the rash and until all the vesicles have crusted over (within 7 - 10 days)
What is the presentation of shingles like?
- may occur due to stress
- there is tingling in a dermatomal distribution
- this is followed by painful skin lesions
- it is unilateral due to a dermatomal distribution (only in one of the trigeminal nerves)
- it can affect any dermatome, but is usually on the trunk
- recovery within 10 - 14 days
What are the investigations for varicella zoster virus?
How is the treatment different for chickenpox in adults and children?
- no investigations are performed - it is a clinical diagnosis
Children:
- supportive treatment to relieve the symptoms
- Calamine lotion to treat itching
- analgesia
- antihistamines
Adults:
- treatment is aimed at treating the virus, rather than the symptoms
- consider aciclovir, valaciclovir or famciclovir if within 24 hours of rash onset
- no treatment is given if the patient presents after 24 hours
What is the treatment for shingles?
- 1st line treatment involves valaciclovir or famciclovir
- 2nd line treatment involves aciclovir
if within 72 hours of appearance of the rash, given for 7 days
What is involved in the prevention of varicella zoster?
VZIG may be indicated in:
- immunosuppressed individuals
-
pregnant women exposed to varicella zoster
- this virus can have teratogenic effects
chickenpox vaccine is licensed in the UK, but no guidelines are available for appropriate use
What can shingles lead to in 15% of elderly patients?
postherpetic neuralgia
this is neuropathic (nerve) pain that occurs due to damage to a peripheral nerve caused by reactivation of VZV
nerve pain tends to be confined to a single dermatome
What are the acute complications of chickenpox?
- bacterial sepsis
- pneumonia
- encephalitis
- haemorrhagic complications
complications are rare in healthy children
What are some of the acute complications of shingles?
- meningoencephalitis
- myelitis
- cranial nerve palsies
- vasculopathy
- gastrointestinal ulcers
- pancreatitis
- hepatitis
complications can also occur without the rash
What are the main clinical features of infectious mononucleosis?
- pharyngitis
- lymphadenopathy (swollen lymph nodes)
- splenomegaly (enlarged spleen)
- there may also be hepatitis
- atypical lymphocytes will be seen
In what types of infections are neutrophils and lymphocytes most commonly seen?
- neutrophils are mostly seen in bacterial infections
- lymphocytes are mostly seen in viral infections
What is the definition of infectious mononucleosis and how common is it?
How is it spread?
it is a clinical syndrome caused by primary EBV infection
- (also known as glandular fever)*
- it affects 90-95% of people at some point in their lives
- EBV is spread by saliva / respiratory droplets
- it infects B lymphocytes and there is incorporation of viral DNA into host DNA
What is the presentation of infectious mononucleosis like?
- fever
- jaundice due to hepatosplenomegaly
- tonsillar exudates due to pharyngitis
- lymphadenopathy affecting the posterior cervical nodes
What “triangle” is used to diagnose infectious mononucleosis?
- there should be fever, pharyngitis and lymphadenopathy on a background of atypical lymphocytosis
What investigations are done for infectious mononucleosis?
- FBC will show lymphocytosis which is highest in week 2-3
- blood film will show atypical lymphocytosis
- Monospot test is performed to look for heterophile antibodies
- EBV specific antibodies
What is involved in the management for infectious mononucleosis?
- management involves supportive care with paracetamol or ibuprofen (anti-inflammatory + analgesics)
-
corticosteroids may be indicated for severe cases
- e.g. haemolytic anaemia, severe tonisillar swelling, obstructive pharyngitis
What is contraindicated in infectious mononucleosis and why?
antibiotics should not be given, especially amoxicillin or ampicillin
these cause a widespread maculopapular rash
What are the 3 components of the EBV specific antibody test?
- EBV viral capsid antigen (VCA) IgM
- indicates current infection
- EBV VCA IgG
- indicates past infection
- Epstein-Barr nuclear antigen (EBNA)
- appears 6 - 12 weeks after onset of symptoms
How can the levels of VCA IgM, VCA IgG and EBNA IgG determine whether someone has had EBV or not?
- in an early primary infection, there will only be VCA IgM
- in an acute primary infection, there will be VCA IgM & IgG
- if someone has had EBV in the past, they will have VCA IgG & EBNA
How does HIV replicate?
- it attaches to the cell and uses reverse transcriptase and integrase to become part of the nuclear genome
- it can then produce viral proteins and replicate
What are the ways in which HIV can be transmitted?
- through sexual contact
- during pregnancy, childbirth & breastfeeding
- injection drug use
- occupational exposure
- blood transfusion or organ transplant
What are the 4 stages of untreated HIV infection (4Fs)?
1 - Flu-like:
- presents with fever, myalgia, fatigue & flu-like symptoms after intial infection
2 - Feeling fine:
- the virus is slowly replicating and during this time there are no symptoms
3 - Falling count:
- virus starts destroying CD4 cells and their numbers dwindle
4 - Final crisis:
- CD4 cells are so low that they cannot fight other infections
- this is an immunocompromised patient with AIDS
What is the reason for the presentation of HIV?
What are 3 common presentations of diseases that occur in someone with HIV?
HIV presentation is due to complications arising from having low levels of CD4+ T cells
- toxoplasmosis infection presents with ring-enhancing lesions on CT-head
- CMV retinitis is caused by herpes virus
- diffuse patchy pneumonia caused by pneumocystitis (PCP)
What is hairy leukoplakia?
What causes it and who is affected?
- irregular, white, painless plaques on the lateral tongue that cannot be scraped off
- mediated by EBV
- occurs in HIV-positive patients and organ transplant recipients
What is the definition of candidiasis?
Who tends to be affected and what causes it?
it is a fungal infection caused by Candida species (Candida albicans) = thrush
- oral colonisation ranges from 40-70% of healthy adults and children
- higher rates of infection are seen in children with carious teeth and adults with dentures
- it is caused by a dimorphic fungus
What are the symptoms of candidiasis and who tends to be affected by them?
-
oral candidiasis and oesophageal thrush affects immunocompromised patients
- this presents with a white exudate that can be scraped off
- vulvovagintis affects diabetics and people who have used antibiotics recently
- diaper rash
- infective endocarditis affects IV drug users
- disseminated candidiasis is most common in neutropenic patients
What are the signs and symptoms of candidiasis?
-
oral candidiasis and oesophageal thrush
- presents with dysphagia
-
vulvovaginitis / balanitis
- presents with thick discharge, itching, redness, soreness
-
disseminated candidiasis
- presents with fever, hypotension +/- leucocytosis
What are the investigations for candidiasis?
it is usually a clinical diagnosis and swabs are not routinely recommended
other investigations may be performed to exclude differentials or risk factors:
- urinalysis (UTI)
- random or fasting blood glucose (diabetes)
- glucose tolerance test (diabetes)
- HIV antibody test
- vaginal pH test (to exclude STIs)
What is Kaposi’s sarcoma and how does it present?
- it is an AIDS-defining condition that is caused by HHV-8
- it presents as a pink or violaceous (purple) patch on the skin or in the mouth
What are other HIV-associated tumours?
- squamous cell carcinoma
- this is particularly cervical or anal and due to HPV
What are the first line investigations for HIV?
- ELISA - confirmed with Western blot
- serum HIV rapid test
- serum HIV DNA PCR in infants
-
CD4 count
- this indicates immune status and assists the staging process
What is the definition of tonsillitis?
How common is it?
acute infection of the parenchyma of the palatine tonsils
it may occur in isolation or as part of generalised pharyngitis
it is very common and is more common in children aged between 5 and 15
What are the common bacterial and viral causes of tonsilitis?
Viral:
- most common are rhinovirus, coronavirus & adenovirus
- associated with IM infection
Bacterial:
- Group A streptococci
- Mycoplasma pneumoniae
- Neisseria gonorrhoea
What are the signs and symptoms of tonsillitis?
- pain on swallowing
- fever > 38
- tonsillar exudate
- sudden onset of a sore throat
- tonsillar erythema and enlargement
- anterior cervical lymphadenopathy
What are the Centor criteria for tonsillitis and how do they determine what investigations should be done?
- tonsillar exudates present
- fever > 38
- anterior cervical lymphadenopathy
- absence of a cough
- if score is 2 or less, then the cause is likely to be viral and no investigations are performed
- if the score is 3 or more then a rapid streptococcal antigen test is performed
What is the definition of the common cold?
How common is it?
mild, self-limiting, viral, upper respiratory tract infection characterised by nasal stuffiness and discharge, sneezing, sore throat and cough
it is very common and adults experience around 2-3 each year
What are the most common causes of the common cold?
- rhinoviruses (50%)
- coronavirus (10-15%)
- influenza (5-15%)
- parainfluenza (5%)
- respiratory syncytial virus (5%)
What are the investigations for the common cold?
What is involved in the management?
- usually it is a clinical diagnosis and no investigations are done
- consider FBC, throat swab, sputum culture, CRP, CXR
- management is with supportive care
- hydration
- analgesics
- antipyretics
- decongestant (oxymetazozline nasal, ipratropium nasal)
- +/- antihistamine, antitussive
What are the signs and symptoms of a common cold?
- runny / blocked nose
- sneezing
- sore throat
- cough
- headache
- malaise and fever
- symptoms usually clear within 7 to 10 days
What is the definition of an abscess?
What usually causes it?
a collection of pus that has built up within a tissue, organ** or **confined space walled off by fibrosis
it is usually caused by bacterial infection
rarely, it can be caused by parasites (developing world) or foreign substances
What is an external abscess and what usually causes it?
an abscess on the skin surface that is either cutaneous or subcutaenous
it is usually caused by Staphylococcus aureus
What are the signs and symptoms of an external abscess?
- erythema
- hot
- oedema
- pain
- loss of function
Where do internal abscesses tend to be found?
- lungs
- brain
- teeth
- kidneys
- tonsils
- perianal abscesses (common in IBD and diabetes)
- incisional abscesses
What are the signs and symptoms of an internal abscess?
the patient is often systemically unwell with pain and fever
What are the investigations performed for an abscess?
- history
- examination
- observations
- it is usually a clinical diagnosis, however USS can be used to help with diagnosis
What is involved in the management for an uncomplicated abscess?
for uncomplicated skin or soft tissue abscesses:
- aspiration
- incision and drainage
there is no need for antibiotics
What is involved in the management for severe abscesses?
for severe abscesses, multiple sites of infection, rapid disease progression, cellulitis & sepsis:
- antibiotics
- incision and drainage
- excision in severe cases
