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PBL Week 6 > Common & important viral diseases > Flashcards

Common & important viral diseases Flashcards

1
Q

What causes chicken pox? How is it spread? Incubation period? Symptoms?

A

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

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2
Q

What causes shingles? Symptoms?

A

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

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3
Q

What is influenza & what are the 3 types of influenza virus?

A

Acute viral infection of respiratory tract

3 types: A, B & C.

Influenza A & B are responsible for most cases.

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4
Q

What is the incubation period?

A

1-3 days

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5
Q

Why is influenza unique among respiratory viruses?

A

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).

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6
Q

Explain the pathogenesis (how a disease develops) of influenza infection.

A

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.

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7
Q

What are the symptoms & complications of influenza?

A

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.

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8
Q

At risk groups for influenza?

A

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

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9
Q

Influenza in pregnant women?

A

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.

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10
Q

How is influenza managed in at risk groups?

A

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!

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11
Q

Treatments for influenza?

A

Neuraminidase inhibitors- antiviral drugs:

  1. Oseltamivir
  2. Zanamivir
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12
Q

What influenza vaccines are available?

A

Live attenuated vaccine (LAIV) - quadrivalent - children

Inactivated influenza vaccine(quadrivalent: H1N1, H3N2, influenza B two subtypes).

Trivalent adjuvanted inactivated vaccine - age over 65+.

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13
Q

What is Norovirus caused by? Incubation period? What does it cause? Symptoms? Diagnosis?

A
  • 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

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14
Q

What causes measles?

A
  • Caused by a Morbillivirus of the Paramyxoviridae family
  • Spread by airborne or droplet transmission
  • Acute viral illness
  • Highly contagious
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15
Q

Why does measles still cause death?

A

Largely due to an increased susceptibility to secondary bacterial & viral infections because of a prolonged state of immunosuppression.

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16
Q

Clinical features of measles?

A

1.Prodromal stage
- Fever
- Malaise- generally feeling unwell
- Coryza - irritation & inflammation of mucous membranes inside nose → runny nose, sneezing…
- Conjunctivitis
- Cough

  1. 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.
  2. . 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

17
Q

When are people infectious w/ measles?

A
  • From beginning of prodromal period
  • To 4 days after appearance of the rash
18
Q

What is the incubation period of measles?

A
  • 7-18 days
  • Average = 10 days
  • W/ further 2 days before the rash appears
19
Q

What are the complications of measles?

A
  • 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.
20
Q

What are the 3 different forms of measles encephalitis?

A
  1. Post-infectious encephalomyelitis - occurs at 1 week after onset of rash.
  2. Measles inclusion body encephalitis - occurs in immunocompromised patients.
    - Characterised by acute neurological compromise & deterioration of consciousness, seizures & progressive neurological damage
  3. SSPE - rare, fatal, late complication of measles infection - 1/25,000 measles infections.
21
Q

Treatment for measles?

A

MMR vaccine- in 1988
- 2 dose MMR schedules introduced in 1996

Cases rising due to Wakefield

22
Q

What is HIV?

A

Progressive deterioration of the immune system that be fatal if untreated

23
Q

Virology of HIV?

A

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.

24
Q

Explain the HIV life cycle?

A
  1. HIV approaches a CD4 T-cell.
  2. Binding: HIV binds w/ glycoproteins to CD4 receptor
  3. Fusion: virus fuses to host cell & releases RNA into it.
  4. Reverse transcription: HIV enzyme reverse transcriptase converts single stranded HIV RNA into double stranded HIV DNA
  5. Integration: HIV DNA enters host’s nucleus & is integrated into host’s DNA using integrase enzyme. Creates a provirus.
  6. 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.
  7. Assembly: the enzyme protease cuts long chains of HIV into individual proteins & assemble a virus particle containing HIV RNA.
  8. 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.
  9. The immature virus breaks free of infected cell.
  10. Maturation: protease completes cutting the HIV protein chains into individual proteins & newly formed copy of HIV can now infect other cells.
25
Q

How can HIV be transmitted?

A

Blood

Semen

Vaginal Secretions

Breast milk

Contact w/: mucous membranes, damaged tissue or injected into body

Through sex, contaminated needles, IV drug use.

26
Q

Groups at highest risk for HIV?

A

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.

27
Q

What are the symptoms of HIV?

A
  1. Fever
  2. Pharyngitis - sore throat
  3. Headache
  4. Myalgia - muscle ache
  5. Arthralgia - joint stiffness
  6. Malaise - generally unwell
  7. Non-pruritic (non-itchy), maculopapular rash on face & trunk.
  8. Generalised lymphadenopathy - swollen glands
28
Q

What are the lab tests of HIV?

A

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)

29
Q

How is HIV infection managed or prevented?

A

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.

30
Q

How do you get AIDS?

A

HIV infected patients develop AIDS in the absence of treatment.

31
Q

What are the systemic & organ specific manifestations of AIDS?

A
  • Opportunistic infections
  • Cancer complications
  • Cardiovascular complications
  • CNS complications
32
Q

When can diagnosis of AID be made?

A
  • When HIV positive patient has a CD4 count of less than 200 or 14%
  • or the patient is diagnosed w/ an AIDS defining condition.
33
Q

What causes Mumps? Symptoms? Diagnosis & treatment?

A

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

34
Q

What causes Rubella? Spread by? Symptoms? Treatment?

A

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

35
Q

What is Hep C? How is it spread? Symptoms? Treatment?

A

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

36
Q

What is Hep B? Symptoms? Goal of treatment? Investigation?

A

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

PBL Week 6 (9 decks)

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