Dengue Fever Flashcards
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
4 - 0.6 cases per 100,000
As likely to occur in males or females
What age does dengue fever typically peak?
1 - 60-70
2 - 30-40
3 - 20-30
4 - 10-20
3 - 20-30
Which of the following is the incidence of Dengue lowest?
1 - South Africa
2 - The Americas
3 - Western Pacific
4 - South-East Asia
1 - South Africa
Dengue fever is typically transmitted via mosquitos. Can this be transmitted from person to person?
- no
Is dengue a virl or bacterial infection?
- viral
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
4 - Pregnancy
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.
4 - Older populations
What is the typical incubation period of dengue fever?
1 - <3 days
2 - <7 days
3 - <11 days
4 - <21 days
3 - <11 days
Can give a clue as to what the infection is
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
4 - all of the above
May also occur in mast cells, dendritic cells, and endothelial cells
Once infected with a specific serotype (grouping of different strains of dengue), does the patient then have immunity against that serotype?
- Yes
BUT may develop severe dengue if infected with a different serotype, this is called antibody-dependent enhancement.
Are all patients with dengue symptomatic?
- no
- 75% are asymptomatic
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
2 - flu like symptoms
Fever typically presents on day 3 and has a high pyrexias ‘break-bone fever’ lasting 3-7 days
Does dengue fever typically cause a high or low neutrophils?
- 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
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
1 - malaria
2 - dengue
Almost always LOW platelets
Is CRP typically higher in viral or bacterial infections?
- bacterial
Viral = lower CRP
Bacterial = higher CRP
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
2 - T cells
Cytokines are also involved
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
1 - >2
Typically these symptoms come on with no warning signs
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
8 - all of the above
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
4 - Haematuria
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
5 - Ocular manifestations:
- Retro-orbital pain
- Conjunctival injection
- Conjunctivitis
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
1 - DIC
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
4 - thrombocytopenia
Closely followed by leucopenia
A positive PCR can confirm dengue fever serotype
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
1 - petechiae in a 2.5cm square on the forearm
Good for using in low funded countries
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)
2 - HPLC
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
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
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?
- 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 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
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)
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
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
If exposed to Dengue previously and you contract Dengue again, are the symptoms worse or the same?
- Symptoms are worse
Higher risk of haemorrhagic fever
and Dengue shock syndrome
