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year 4 CDM 2 > Case 12: Influenza, dengue > Flashcards

Case 12: Influenza, dengue Flashcards

1
Q

Position for LP

A
  • Patient lying on their side. Knees, hip and neck flexed.
  • Can do it with patients sitting but then cant measure opening pressure.
  • Needle inserts below the conus medularis at L4/5 disc space.
  • Ideally US guided
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2
Q

LP appearance

A
  • Normal - clear (‘gin-coloured’)
  • Cloudy/purulent - meningitis
  • Blood-stained - subarachnoid haemorrhage, or a traumatic tap
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3
Q

LP opening pressure

A
  • Normal is 8-20cm
  • May be elevated due to infection, inflammation, haemorrhage and idiopathic intracranial hypertension
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4
Q

LP white blood cells

A
  • Normal – 0-5 cells/ul
  • ↑ neutrophils – bacterial meningitis
  • ↑ lymphocytes – viral & TB meningitis/ encephalitis, (& inflammatory conditions, malignancy)
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5
Q

LP: protein

A
  • Normal - 0.15-0.45 g/L
  • ↑infection (TB > bacterial > viral), inflammatory conditions, Guillain-Barre syndrome
  • Oligoclonal bands in multiple sclerosis
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6
Q

LP: glucose

A
  • Paired with blood glucose
  • Normal - 60-80% of serum glucose
  • ↓ (<50%) in infection (esp. bacterial, TB and fungal)
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7
Q

LP gram stain

A
  • Gram positive: Dark purple- Strep pneumoniae cocci in pairs/short chains
  • Gram negative: Pink- Neisseria meningitidis diplococci
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8
Q

Streptococci under the microscope

A
  • Streptococci: gram positive cocci (round or oval shaped)
  • Strep pneumoniae – tends to form typically lancet shape and group in pairs
  • Enterococci (a subset of Streptococci) – tend to form short chains
  • Oral (viridans) Streptococci – can form long chains
  • Strep pyogenes – medium to long chain
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9
Q

Steps in identifying Streptococci: order

A

Microscopy → Culture and colonial appearance (Catalase) → Haemolysis → Further identification → Susceptibility testing

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10
Q

Culture appearance Streptococci and Catalase test

A

Culture appearance Streptococci: greyish white colonies. Staphylococci appear similar to Streptococci. Cultures grow in 24-48hrs

Catalase test: Staphylococci produce bubbles and are catalase positive. Streptococci are catalase negative (no bubbles)

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11
Q

Streptococcus haemolysis classification

A
  • Alpha- haemolytic (green, partial haemolysis): Pneumoniae, Viridans
  • Beta-haemolytic- clear, complete haemolysis: Pyogenes, agalactiae
  • Gamma-haemolytic- no haemolysis (red): Enterococcus
  • Have to hold the plate up to the light
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12
Q

Further identification of Streptococcus

A
  • Not always needed but is needed in IE, used to identify the specific species
  • Mass spectrometry
  • Panel of biochemical reactions
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13
Q

Susceptibility testing

A
  • Disc diffusion method: shows what antibiotics bacteria are susceptible and resistant to
  • MIC testing (E-tests) used for for long courses of antibiotics (complicated or deep). More specific then disc testing, shows how sensitive it is
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14
Q

Influenza: clinical features

A
  • fever greater than 38ºC
  • myalgia
  • lethargy
  • headache
  • rhinitis
  • sore throat
  • cough
  • diarrhoea and vomiting
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15
Q

Consider prescribing anti-retroviral treatment for influenza if the following applies

A
  • The patient is in an at-risk group or is felt to be at risk of developing a serious complication
  • There is circulating influenza nationally
  • The patient is able to start treatment within 48 hours from the onset of symptoms (36 hours for zanamivir)
  • Can get antivirals if in hospital and have contact with flu for prophylaxis
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16
Q

Antiretrovirals for influenza

A
  • First line: oseltamivir (oral)
  • Second line: zanamivir (inhaled
  • Needed to be started within 48hrs of symptom onset given for 5 days
  • For immunocompromised adults and in renal impairment: zanamivir
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17
Q

Influenza virus

A
  • RNA virus
  • Types A, B and C effect humans
  • Type A has H and N subtypes
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18
Q

Who is offered the free flu vaccine

A
  • Aged 65 and over
  • Young children
  • Pregnant women
  • Chronic health conditions, such as asthma, COPD, heart failure and diabetes
  • Healthcare workers and carers
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19
Q

Flu testing

A
  • UK Health Security Agency: monitors the number of flue cases
  • Point of care tests: give a rapid result dont give information about subtype
  • PCR: from viral nasal or throat swabs
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20
Q

Flu- post exposure prophylaxis criteria

A
  • It is started within 48 hoursof close contact with influenza
  • Increased risk(e.g., chronic disease or immunosuppression)
  • Not protectedby vaccination (e.g., it has beenless than 14 dayssince they were vaccinated)
  • Options: Oseltamivir or zanamivir for 10 days
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21
Q

Complications for influenza

A
  • Otitis media, sinusitis and bronchitis
  • Viral pneumonia
  • Secondary bacteria pneumonia
  • Worsening chronic health conditions, such as COPD and heart failure
  • Febrile convulsions (young children)
  • Encephalitis
22
Q

Types of influenza

A
  • Influenza A and B belong to the Orthomyxociridae virus family
  • Type A influenza: most common and severe, more likely to cause pandemics
23
Q

Bronchiolitis

A
  • Fever, widespread crepitations, occasionally conjunctivitis
  • RSV most common cause
  • Most children have been infected by 2
  • Seasonal- winter illness
  • Treatment is supportive
24
Q

Covid

A
  • Diagnosed with Viral PCR
  • Can be mild-severe
  • Vaccinations
  • Treatment with anti-virals in severe cases
25
Q

Dengue epidemiology

A
  • Arbovirus transmitted by the female aedes mosquito
  • Centred between the topics of Cancer and Capricorn particularly South East Asia and South America
  • 4 different serotypes (DEN-1, DEN-2, DEN-3, DEN-4): Only develop immunity to the serotype you are infected with
  • 4-10 day incubation period
  • Notifiable disease
26
Q

Severe dengue is more likely to develop in

A
  • Children under 15 years old
  • Repeated dengue infections
  • Specific viral genotypes: DEN-2 and DEN-3
  • Malnourished children.
27
Q

Timings of dengue fever

A
  • Fevertypically starts on day 3
  • Lasts for 5-6 days (viraemic phase): Can then recover or progress to severe dengue
  • Mild haemorrhagic symptoms
  • Dengue fever is rarely fatal
  • Incubation period:4-10 days
  • Initially flu like illness, more severe with each infection. Can present anything from undifferentiated fever to life threatening shock
28
Q

The three phases of dengue

A
  1. febrile phase (2-7 days): normal WBC, platelet and Haematocrit
  2. critical phase (only in those with severe dengue) (24-48hrs): shock and bleeding. fluids leak into the extravascular compartment. Drop in WBC, platelets and increased HCT
  3. recovery phase: Reabsorption of extravascular fluid. No fluid loss. Normal WBC, platelet and Haematocrit
    - PCR viral load increases in Febrile phase and IgM/IgG increases in critical and recovery phrase
29
Q

Diagnostic criteria for probable dengue

A
  1. live in or travel to endemic area
  2. fever
  3. two of: N/V, rash, aches and pains, positive torniquet test, leukopenia or any warning sign
30
Q

Pathophysiological response in severe dengue

A

Increased vascular permeability causing plasma leakage into tissues. Causes cytokine response and suppression of T-cell response. Don’t fluid overload as there is fluid reabsorption in the recovery phase

31
Q

Dengue presentation

A

Dengue can be asymptomatic (75%) or present as a non-specific febrile illness (25%), especially in young children. Dengue has a broad clinical spectrum ranging from a mild flu-like illness to severe haemorrhagic, shock and multi-organ failure.

32
Q

Non severe dengue: fever followed by recovery

A
  • Without warning- fever with two or more of the following: nausea/vomiting, rash, aches and pains, positive tourniquet test, Leukopenia
  • With warning signs: abdo pain, persistent vomiting, clinical fluid accumulation (oedema), mucosal bleed, lethargy, restlessness, liver enlargement >2cm, increasing haematocrit with reducing platelets
33
Q

Initial presentation of dengue fever

A
  • Intermittent high fevers lasting 3-7 days
  • Arthralgia
  • Rash: blanching maculopapular erythematous rash similar to measles, may cause petechiae
  • Bleeding gums, epistaxis, GI bleeds
34
Q

Diagnostic criteria for severe dengue: any of the following

A
  1. severe plasma leakage: shock (dengue shock syndrome), fluid accumulation with respiratory distress
  2. severe haemorrhage
  3. severe organ impairment: Liver AST/ALT above 100 (AST or ALT >1000), CNS impaired consciousness, heart failure
35
Q

Severe dengue (5% of patients)

A
  • Dengue with severe plasma leakage, severe haemorrhage and severe organ impairement. Symptoms:
  • Pulmonary and facial oedema
  • Ascites
  • Pleural effusions
  • Meningism including photophobia
  • Worsening or more profuse haemorrhage
36
Q

Dengue bloods

A
  • Thrombocytopaenia and Leukopaenia
  • Prolonged APTT and PT
  • Deranged U&E’s
  • Elevated LFT’s especially ASR
37
Q

Dengue investigations

A
  • Viral isolation from serum
  • PCR: detection of viral antigen NS1, done up to 5 days after fever
  • ELISA: IgM and IgG. Done after day 5 using rapid testing kits.
  • Tourniquet test: not very sensitive. Inflate a BP cuff to halfway between systolic and diastolic pressure for 5 mins. A positive test shows 20+ petechiae in a 2.5cm square on the forearm
  • CXR: look for pleural effusions
38
Q

Diagnosing dengue: 5 days or less post fever

A
  • PCR: viral RNA
  • PCR: viral antigen (NS1)
39
Q

Diagnosing dengue (5 days or more post fever onset)

A
  • IgM antibodies ELISA: last up to 6 months
  • IgG antibodies ELISA: last a lifetime, suggest past infection

What can ELISA distinguish: primary (first flavivirus exposure) from secondary (previously exposed to different flavivirus)

40
Q

Management for dengue fever

A
  • No specific treatment, only admit to hospital if warning signs of severe dengue
  • Non-severe: conservative treatment with oral fluids and paracetamol. Avoid aspirin
  • Severe cases: IV fluids with monitoring to prevent fluid overload, regular observation and monitoring, might require high dependency or Intensive Care
  • Severe GI haemorrhage (if deterioration): may require blood transfusion +/- FFP
  • Avoid NSAID (may exacerbate haemorrhage)
  • Recovery: prevent overload
41
Q

Preventative measures for dengue fever

A
  • PPE
  • DEET: long sleeved clothing
  • Vaccine: can precipitate severe cases of dengue if previously immunised
42
Q

Complications of dengue

A
  • Severe dengue: multi-organ involvement, haemorrhage and shock. 50% mortality if untreated
  • Hepatic failure
  • Encephalopathy
  • Myocarditis
  • Disseminated intravascular coagulation
  • Septicaemia
43
Q

Rickettsia

A
  • Three classifications: Spotted fever, Typhus fever, Scrub fever
  • An acute, febrile, infectious disease which is caused by the organism Orientia tsutsugamushi (Gram -, coccobacilli
  • Eschar, regional lymphadenopathy, fever, Maculopapular rash, leukopenia
  • Treated with: Chloramphenicol and Tetracycline
44
Q

Riskettsia epidemiology

A
  • Source of infection= Rat
  • Route of transmission= Trombiculid mites, ticks, lice, fleas which are found on large mammals
  • Spread by haematogenous or lymphatic system
  • Epidemic features= Tsutsugamushi triangle (South East Asia)
  • Infection to one serotype causes lifelong immunity to only that serotype
45
Q

Rickettsia clinical features

A
  • Inoculation: Papule, maculopapular rash (chest, abdomen), Eschar, ulcer
  • Invade local lymph node: Enlargement of local lymph node (tenderness and enlargement)
  • Spread by blood stream: General symptoms of sepsis
  • Invade vascular endothelium: Generalised hyperaemia, systemic lymphadenopathy
46
Q

Rickettsia clinical manifestations with timings

A
  • Incubation period is 4~21 days
  • Sudden onset with a fever
  • 1st week, systemic toxic symptoms
  • 2nd week, get worse, complication
  • 3th week, convalesce
47
Q

Eschar

A

Found in the axillary fossa, inguinal region, perianal region, scrotum, buttocks and the thigh. Is an ulcer surrounded by a red areola often covered by a dark scab.

48
Q

Rickettsia: Laboratory examination

A
  • Haematology: Leukopenia, normal WBC, elevation with some complications
  • Biochemical: injury of liver function, CRP
  • Weil-Felix with OX19: can be positive from 4th day. Easy and accessible but poor sensitivity (Gold standard)
  • IFA and HP test: positive at end of 1st week, lasts for years
  • Blood culture
  • Spleen and Liver biopsies stained with Giemsa
  • PCR: Not routinely available
49
Q

Treatment: Rickettsia disease

A
  • Sensitive antibiotics: Chloramphenicol, Doxycycline
  • Strains resistant to doxycycline and chloramphenical= Use a combination of Doxycycline and Rifampicin or Azithromycin
  • General: supportive IV fluids, intensive nursing care and prevent complications
50
Q

Risk factors and protective for malaria

A

Risk factors for malaria mortality: Pregnancy, neonatal, Sub-Saharan Africa

Protective for malaria: long sleeves, insecticide coated bed net, insect repellent

51
Q
A

year 4 CDM 2 (39 decks)

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