Common & important viral diseases Flashcards
What causes chicken pox? How is it spread? Incubation period? Symptoms?
Varicella zoster virus (VZV)
- Highly infectious
Spread by aerosol and direct contact
- Primary infection usually produced in childhood
Incubation period 11-20 days
Presents as a vesicular eruption (rash) - small pink macules (spots) that progress into vesicles and pustules
- Diagnosis by recognition of the rash
What causes shingles? Symptoms?
Herpes zoster virus:
- After initial infection (chicken pox), varicella zoster virus persists in latent form in the dorsal root ganglion of sensory nerves & can reactivate in later life
Presents w/ pain described as burning or stabbing, followed by vesicular rash in the affected dermatome
What is influenza & what are the 3 types of influenza virus?
Acute viral infection of respiratory tract
3 types: A, B & C.
Influenza A & B are responsible for most cases.
What is the incubation period?
1-3 days
Why is influenza unique among respiratory viruses?
Frequent antigen changes
Seasonality
- changes in hemagglutinin neuraminidase (HN) glycoproteins on surface of virus
Impact on general pop.
- can cause explosive outbreaks & can cause substantial mortality (particularly in people with chronic illnesses).
Explain the pathogenesis (how a disease develops) of influenza infection.
Initial site of infection is mucosa in the respiratory tract.
- Infection is caused by HA binding to syalilated glycans on epithelial cells.
Infection causes degeneration of respiratory epithelial cells w/ loss of:
- ciliated tufts, desquamation, oedema, hyperemia (an excess of blood in the vessels supplying an organ) & mononuclear cell infiltrates.
What are the symptoms & complications of influenza?
Symptoms:
- Cough
- Fever & chills
- Malaise
Complications
- Lower respiratory tract infection
- Admission to hospital
- Death
NOTE: All depends on factors such as age, co-morbidities & type of co-morbidity.
At risk groups for influenza?
a) Chronic respiratory system diseases e.g. COPD, asthma
b) Cardiovascular system diseases e.g. Heart disease
c) Endocrine system diseases e.g. diabetes
d) Hepatic system disease e.g. Liver failure, jaundice, Hepatitis
e) Renal system diseases e.g. Chronic kidney disease
f) Neurological/neuromuscular conditions e.g. MS
h)Immunosuppression - due to HIV, cancer, blood conditions
i) Pregnant women
Influenza in pregnant women?
PHE recommends immunisation.
Mortality in pregnancy w/ flu usually due to overwhelming pulmonary disease
x 2-4 fold increased risk of complications w/ increasing stage of pregnancy —> pneumonia, preterm delivery, perinatal mortality, foetal distress.
How is influenza managed in at risk groups?
Immunisation w/ inactive vaccine
Clinicians should suspect flu in at risk patients w/ lower respiratory tract infections
treat using ‘educated guess’ whilst waiting for PCR results i.e. don’t wait to treat!
Treatments for influenza?
Neuraminidase inhibitors- antiviral drugs:
- Oseltamivir
- Zanamivir
What influenza vaccines are available?
Live attenuated vaccine (LAIV) - quadrivalent - children
Inactivated influenza vaccine(quadrivalent: H1N1, H3N2, influenza B two subtypes).
Trivalent adjuvanted inactivated vaccine - age over 65+.
What is Norovirus caused by? Incubation period? What does it cause? Symptoms? Diagnosis?
- Virus - norovirus
- Incubation period= 24-48 hours
- Most common cause of infectious gastroenteritis
- Symptoms= vomiting, diarrhoea & stomach cramping
- Diagnosis may be achieved by electron microscopy, antigen or DNA detection (PCR) in stool samples
Virus is highly infectious& cases should be isolated & environmental surfaces cleaned w/ detergents & disinfected w/ bleach
What causes measles?
- Caused by a Morbillivirus of the Paramyxoviridae family
- Spread by airborne or droplet transmission
- Acute viral illness
- Highly contagious
Why does measles still cause death?
Largely due to an increased susceptibility to secondary bacterial & viral infections because of a prolonged state of immunosuppression.
Clinical features of measles?
1.Prodromal stage
- Fever
- Malaise- generally feeling unwell
- Coryza - irritation & inflammation of mucous membranes inside nose → runny nose, sneezing…
- Conjunctivitis
- Cough
- Koplik’s Spots
- Small red spots w/ blueish-white centres
- Occur inside cheeks
- May appear on mucous membranes of mouth 1-2 days before the rash appears
- May be seen for a further 1-2 days afterwards. - . Rash
- Erythematous - abnormal redness
- Maculopapular - rash that contains both macules (flat discoloured area) & papules (small raised bump).
- Starts at head & spreads to trunk & limbs over 3-4 days
NOTE- view images on notes
When are people infectious w/ measles?
- From beginning of prodromal period
- To 4 days after appearance of the rash
What is the incubation period of measles?
- 7-18 days
- Average = 10 days
- W/ further 2 days before the rash appears
What are the complications of measles?
- Otitis media- infection of middle ear
-Pneumonia - Diarrhoea
- Convulsions
- Encephalitis - inflammation of active tissues of the brain- Can lead to headache, stiff neck, light sensitivity, seizures, confusion.
- Subacute sclerosing pan-encephalitis (SSPE) - progressive neurological disorder in children & young adults that affects CNS.
What are the 3 different forms of measles encephalitis?
- Post-infectious encephalomyelitis - occurs at 1 week after onset of rash.
- Measles inclusion body encephalitis - occurs in immunocompromised patients.
- Characterised by acute neurological compromise & deterioration of consciousness, seizures & progressive neurological damage - SSPE - rare, fatal, late complication of measles infection - 1/25,000 measles infections.
Treatment for measles?
MMR vaccine- in 1988
- 2 dose MMR schedules introduced in 1996
Cases rising due to Wakefield
What is HIV?
Progressive deterioration of the immune system that be fatal if untreated
Virology of HIV?
2 types:
- HIV-1
- HIV-2
Enveloped viruses
RNA viruses
- reverse transcribe their genome to form double-stranded DNA which integrates into host’s DNA.
Explain the HIV life cycle?
- HIV approaches a CD4 T-cell.
- Binding: HIV binds w/ glycoproteins to CD4 receptor
- Fusion: virus fuses to host cell & releases RNA into it.
- Reverse transcription: HIV enzyme reverse transcriptase converts single stranded HIV RNA into double stranded HIV DNA
- Integration: HIV DNA enters host’s nucleus & is integrated into host’s DNA using integrase enzyme. Creates a provirus.
- Transcription: the provirus becomes active & uses RNA polymerase & mRNA to create copies of HIV genomic material. - mRNA is used as blueprint to make long chains of HIV proteins.
- Assembly: the enzyme protease cuts long chains of HIV into individual proteins & assemble a virus particle containing HIV RNA.
- Budding: the newly assemble virus buds form the host cell taking w/ it a part of the cell’s outer envelope
-This covering is a mixture of protein & sugar forming the HIV glycoproteins. - The immature virus breaks free of infected cell.
- Maturation: protease completes cutting the HIV protein chains into individual proteins & newly formed copy of HIV can now infect other cells.
How can HIV be transmitted?
Blood
Semen
Vaginal Secretions
Breast milk
Contact w/: mucous membranes, damaged tissue or injected into body
Through sex, contaminated needles, IV drug use.
Groups at highest risk for HIV?
LGBTQ+ community
People who inject drugs
Perinatal transmission during pregnancy, labour & delivery, or breastfeeding.
Occupational exposure via needle stick or exposure to eyes, nose, or open wound
Blood transfusion or organ donation from an HIV infected donor.
What are the symptoms of HIV?
- Fever
- Pharyngitis - sore throat
- Headache
- Myalgia - muscle ache
- Arthralgia - joint stiffness
- Malaise - generally unwell
- Non-pruritic (non-itchy), maculopapular rash on face & trunk.
- Generalised lymphadenopathy - swollen glands
What are the lab tests of HIV?
CD4 count - measures state of person’s immune function.
- Adult values approx 500 - 1300
- Used to determine stage of HIV
HIV-1 virus - involves antibody/antigen detection in blood
-detects amount of virus present
- monitors effectiveness of Antiretrovirals (ARVs)
How is HIV infection managed or prevented?
No cure for HIV
Antiretroviral drugs can control virus & help prevent onward transmission.
- Always use 3 or more different ARV meds that work in different ways. Essential for preventing AIDS.
Oral pre-exposure prophylaxis is used by HIV-negative people to block acquisition of HIV.
Post-exposure prophylaxis use of antiretrovirals w/in 72 hrs prevents HIV infection.
How do you get AIDS?
HIV infected patients develop AIDS in the absence of treatment.
What are the systemic & organ specific manifestations of AIDS?
- Opportunistic infections
- Cancer complications
- Cardiovascular complications
- CNS complications
When can diagnosis of AID be made?
- When HIV positive patient has a CD4 count of less than 200 or 14%
- or the patient is diagnosed w/ an AIDS defining condition.
What causes Mumps? Symptoms? Diagnosis & treatment?
Caused by:
- Paramyxovirus
- Systemic viral infection
Symptoms:
- swelling of the parotid glands (salivary gland)
- Pyrexia (high fever) - headache precede swelling
Diagnosed clinically, but salivary mumps IgM can be done
- Symptom relief w/ analgesia
What causes Rubella? Spread by? Symptoms? Treatment?
Rubella virus
Spread by droplet infection
Symptoms:
- mild fever
- generalised rash
- lymphadenopathy (swollen lymph nodes)
- conjunctivitis
- arthralgias or arthritis
Maternal infection in pregnancy, particularly early in gestation, may cause spontaneous abortion
Immunisation - MMR vaccine offered in childhood
What is Hep C? How is it spread? Symptoms? Treatment?
An inflammation of liver caused by the hepatitis C virus
Most common type of viral hepatitis in UK
Can become infected if you come into contact w/ the blood of an infected person
Symptoms:
- No noticeable symptoms until liver has been significantly damaged
Treatment:
- Oral direct-acting antiviral therapies
What is Hep B? Symptoms? Goal of treatment? Investigation?
Most common liver infection globally
Symptoms:
- Most people are asymptomatic
- some will present w/ complications such as cirrhosis, hepatocellular carcinoma, or liver failure
Goal of treatment = to improve survival & QOL by preventing disease progression.
- Current treatments do not completely eradicate the virus
Investigations- liver function tests, FBC, urea & electrolytes, coagulation profile
