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A. Block E Microbiology > Dengue Fever > Flashcards

Dengue Fever Flashcards

1
Q

Dengue fever is a globally important arbovirus transmitted by the aedes mosquito. What is the incidence of dengue fever?

1- 6000 cases per 100,000
2 - 600 cases per 100,000
3 - 60 cases per 100,000
4 - 0.6 cases per 100,000

A

4 - 0.6 cases per 100,000

As likely to occur in males or females

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2
Q

What age does dengue fever typically peak?

1 - 60-70
2 - 30-40
3 - 20-30
4 - 10-20

A

3 - 20-30

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3
Q

Which of the following is the incidence of Dengue lowest?

1 - South Africa
2 - The Americas
3 - Western Pacific
4 - South-East Asia

A

1 - South Africa

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4
Q

Dengue fever is typically transmitted via mosquitos. Can this be transmitted from person to person?

A
  • no
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5
Q

Is dengue a virl or bacterial infection?

A
  • viral
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6
Q

Which of the following is NOT a risk factors for Dengue fever?

1 - Visiting a dengue-endemic region
2 - High population density
3 - Poor standards of hygiene
4 - Pregnancy

A

4 - Pregnancy

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7
Q

Severe dengue is LEAST likely to develop in which of the following:

1 - Children under 15 years old
2 - Repeated dengue infections
3 - Specific viral genotypes
4 - Older populations
5 - Malnourished children.

A

4 - Older populations

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8
Q

What is the typical incubation period of dengue fever?

1 - <3 days
2 - <7 days
3 - <11 days
4 - <21 days

A

3 - <11 days

Can give a clue as to what the infection is

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9
Q

Once a patient is infected with Dengue fever, the virus is then able to replicate in which of the following cells?

1 - macrophages
2 - monocytes
3 - B cells
4 - all of the above

A

4 - all of the above

May also occur in mast cells, dendritic cells, and endothelial cells

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10
Q

Once infected with a specific serotype (grouping of different strains of dengue), does the patient then have immunity against that serotype?

A
  • Yes

BUT may develop severe dengue if infected with a different serotype, this is called antibody-dependent enhancement.

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11
Q

Are all patients with dengue symptomatic?

A
  • no
  • 75% are asymptomatic
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12
Q

All of the following are symptoms of dengue fever, but which of the following presents 1st?

1 - fever
2 - flu like symptoms
3 - mild hemorrhagic symptoms
4 - rash

A

2 - flu like symptoms

Fever typically presents on day 3 and has a high pyrexias ‘break-bone fever’ lasting 3-7 days

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13
Q

Does dengue fever typically cause a high or low neutrophils?

A
  • low

Intracellular = low neutrophils
Pathogens MUST enter cells to replicate

Extracellular = high neutrophils
Pathogens do NOT need to enter cells to replicate

If pathogen is inside the cell the neutrophils cannot target it, and therefore neutrophils are low

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14
Q

If a patients platelets are normal, which 2 of the following would you rule out?

1 - malaria
2 - dengue
3 - enteric fever
4 - lyme disease

A

1 - malaria
2 - dengue

Almost always LOW platelets

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15
Q

Is CRP typically higher in viral or bacterial infections?

A
  • bacterial

Viral = lower CRP
Bacterial = higher CRP

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16
Q

Severe dengue is associated with increased vascular permeability due to capillary leakage causing plasma leakage into tissues. This is due to the down regulation of which cell?

1 - macrophages
2 - T cells
3 - B cells
4 - neutrophils

A

2 - T cells

Cytokines are also involved

17
Q

A diagnosis of non severe Dengue includes how many of the following:

  • Nausea/vomiting
  • Rash
  • Aches and pains
  • Positive tourniquet test
  • Leukopenia
  • Elevated haematocrit

1 - >2
2 - >3
3 - >4
4 - all features

A

1 - >2

Typically these symptoms come on with no warning signs

18
Q

Which of the following abdominal symptoms can present with Dengue?

1 - abdominal pain and/or tenderness
2 - persistent vomiting
3 - clinical fluid accumulation
4 - mucosal bleed and lethargy
5 - restlessness
6 - liver enlargement >2cm
7 - increasing haematocrit with reducing platelets
8 - all of the above

A

8 - all of the above

19
Q

Dengue can cause all of the following bleeding related features, EXCEPT which one?

1 - petechial rash
2 - Bleeding gums
3 - Epistaxis
4 - Haematuria
5 - GI bleeds

A

4 - Haematuria

20
Q

Dengue fever can cause all of the following, but which of the following symptoms is a tell tale sign of Dengue fever?

1 - Headache
2 - Nausea & vomiting
3 - Lymphadenopathy
4 - Generalised myalgia and backache
5 - Ocular manifestations:
- Retro-orbital pain
- Conjunctival injection
- Conjunctivitis

A

5 - Ocular manifestations:
- Retro-orbital pain
- Conjunctival injection
- Conjunctivitis

21
Q

Which of the following is NOT a severe symptoms of Dengue fever?

1 - DIC
2 - Pulmonary and facial oedema
3 - Ascites
4 - Pleural effusions
5 - Meningism including photophobia
6 - Worsening or more profuse haemorrhage

A

1 - DIC

22
Q

Although there is no definitive test to diagnose Dengue, lots of tests can be performed. All of the following can occur, but which occurs in 80% of patients?

1 - prolongation of APTT and PT
2 - U&Es
3 - LFTS (AST especially)
4 - thrombocytopenia
5 - leucopenia
6 - increased haematocrit
7 - PCR

A

4 - thrombocytopenia

Closely followed by leucopenia

A positive PCR can confirm dengue fever serotype

23
Q

A turniquet can be performed, where a BP cuff is inflated to halfway between SBP and DBP for 5 mins. A positive test will show what?

1 - petechiae in a 2.5cm square on the forearm
2 - erythema migrans
3 - urticaria
4 - pallor in whole arm

A

1 - petechiae in a 2.5cm square on the forearm

Good for using in low funded countries

24
Q

In specialist centres, all of the following can be used to confirm the presence of the Dengue virus, EXCEPT which one?

1 - PCR
2 - HPLC
3 - blood smear
4 - ELISA (IgG and IgM)

A

2 - HPLC

25
Q

What is the treatment of choice in non-severe cases of dengue?

1 - oral fluids and paracetamol
2 - IV fluid and paracetamol
3 - Antivirals
4 - Steroids

A

1 - oral fluids and paracetamol

No specific treatment for Dengue, so symptom management

Monitoring of haematocrit, platelets and renal function as patient may decline rapidly and need ICU support

26
Q

27 y nurse presents with 2/7 fever, headache, sore throat, chest pain, dry cough and nosebleeds. He returned 2 weeks previously from rural Sierra Leone where he had been volunteering at a rural clinic. Look at the blood results, which aspects would make you rule out Malaria, Dengue Fever and Enteric Fever?

A
  • CRP is <70, suggest viral so enteric fever is out
  • LFTs are normal so malaria and dengue fever unlikely
  • negative malria film rules out malaria
  • abdo NAD rules out Malaria, Dengue Fever and Enteric Fever
27
Q

27 y nurse presents with 2/7 fever, headache, sore throat, chest pain, dry cough and nosebleeds. He returned 2 weeks previously from rural Sierra Leone where he had been volunteering at a rural clinic. Look at the blood results, which of the following are likely diagnoses?

1 - Lassa Fever
2 - Ebola
3 - Marburg Haemorrhagic fever
4 - Crimean Congo Haemorrhagic fever
5 - all of the above

A

5 - all of the above

All can occur in rural W. Africa
Exposure to rats, bats, funerals, and healthcare facilities
Incubation period up to 3/52
Infection control / sample handling implications
(patient isolation –universal precautions, alert lab, minimum samples, double bag, deliver by hand rather than vacuum system)

28
Q

A 34 yr old male presents to his GP with fever, rigors and myalgia ++. Started 4 days after returning from 1/52 holiday in Madeira (Portuguese island) in a 4 star hotel, beach holiday.

His results are as follows:
- T 39.5oC BP: 109/65, Pulse 95
- Cervical lymphadenopathy
- CVS, RS: NAD
- 1cm hepatomegaly
- Generalised rash
- Insect bites ++
- Hb: 15.2, WCC: 6.5, Lymphocytes: 0.8
- Plts: 76
- CRP 32
- Malaria film: negative
- Blood cultures neg

Which of the following is the most likely diagnosis?

1 - Malaria
2 - Dengue Fever
3 - Lyme disease
4 - Enteric Fever

A

2 - Dengue Fever

  • Insect bites and no mention of poor food or water rules out enteric fever
  • Enteric Fever typically presents after >11 days, so rules this out
  • <70 CRP rules out bacterial cause, so enteric fever and Lyme disease
  • Negative blood film rules out malaria, leaving Dengue fever
  • Low platelets and leukopenia also suggest dengue fever
29
Q

If exposed to Dengue previously and you contract Dengue again, are the symptoms worse or the same?

A
  • Symptoms are worse

Higher risk of haemorrhagic fever
and Dengue shock syndrome

A. Block E Microbiology (38 decks)

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