Dengue Fever

Question 1

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

Answer 1

4 - 0.6 cases per 100,000

As likely to occur in males or females

Question 2

What age does dengue fever typically peak?

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

Answer 2

3 - 20-30

Question 3

Which of the following is the incidence of Dengue lowest?

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

Answer 3

1 - South Africa

Question 4

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

Answer 4

• no

Question 5

Is dengue a virl or bacterial infection?

Answer 5

• viral

Question 6

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

Answer 6

4 - Pregnancy

Question 7

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.

Answer 7

4 - Older populations

Question 8

What is the typical incubation period of dengue fever?

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

Answer 8

3 - <11 days

Can give a clue as to what the infection is

Question 9

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

Answer 9

4 - all of the above

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

Question 10

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

Answer 10

• Yes

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

Question 11

Are all patients with dengue symptomatic?

Answer 11

• no
• 75% are asymptomatic

Question 12

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

Answer 12

2 - flu like symptoms

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

Question 13

Does dengue fever typically cause a high or low neutrophils?

Answer 13

• 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

Question 14

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

Answer 14

1 - malaria
2 - dengue

Almost always LOW platelets

Question 15

Is CRP typically higher in viral or bacterial infections?

Answer 15

• bacterial

Viral = lower CRP
Bacterial = higher CRP

Question 16

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

Answer 16

2 - T cells

Cytokines are also involved

Question 17

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

Answer 17

1 - >2

Typically these symptoms come on with no warning signs

Question 18

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

Answer 18

8 - all of the above

Question 19

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

Answer 19

4 - Haematuria

Question 20

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

Answer 20

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

Question 21

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

Answer 21

1 - DIC

Question 22

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

Answer 22

4 - thrombocytopenia

Closely followed by leucopenia

A positive PCR can confirm dengue fever serotype

Question 23

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

Answer 23

1 - petechiae in a 2.5cm square on the forearm

Good for using in low funded countries

Question 24

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)

Answer 24

2 - HPLC

Question 25

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

Answer 25

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

Question 26

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?

Answer 26

- 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

Question 27

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

Answer 27

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)

Question 28

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

Answer 28

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

Question 29

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

Answer 29

- Symptoms are worse Higher risk of haemorrhagic fever and Dengue shock syndrome