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
2
Q
LP appearance
A
- Normal - clear (‘gin-coloured’)
- Cloudy/purulent - meningitis
- Blood-stained - subarachnoid haemorrhage, or a traumatic tap
3
Q
LP opening pressure
A
- Normal is 8-20cm
- May be elevated due to infection, inflammation, haemorrhage and idiopathic intracranial hypertension
4
Q
LP white blood cells
A
- Normal – 0-5 cells/ul
- ↑ neutrophils – bacterial meningitis
- ↑ lymphocytes – viral & TB meningitis/ encephalitis, (& inflammatory conditions, malignancy)
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
6
Q
LP: glucose
A
- Paired with blood glucose
- Normal - 60-80% of serum glucose
- ↓ (<50%) in infection (esp. bacterial, TB and fungal)
7
Q
LP gram stain
A
- Gram positive: Dark purple- Strep pneumoniae cocci in pairs/short chains
- Gram negative: Pink- Neisseria meningitidis diplococci
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
9
Q
Steps in identifying Streptococci: order
A
Microscopy → Culture and colonial appearance (Catalase) → Haemolysis → Further identification → Susceptibility testing
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)
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
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
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
14
Q
Influenza: clinical features
A
- fever greater than 38ºC
- myalgia
- lethargy
- headache
- rhinitis
- sore throat
- cough
- diarrhoea and vomiting
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
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
17
Q
Influenza virus
A
- RNA virus
- Types A, B and C effect humans
- Type A has H and N subtypes
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
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
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
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
Dengue epidemiology
- 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
Severe dengue is more likely to develop in
- Children under 15 years old
- Repeated dengue infections
- Specific viral genotypes: DEN-2 and DEN-3
- Malnourished children.
27
Timings of dengue fever
- Fever typically 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
The three phases of dengue
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
Diagnostic criteria for probable dengue
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
Pathophysiological response in severe dengue
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
Dengue presentation
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
Non severe dengue: fever followed by recovery
- 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
Initial presentation of dengue fever
- 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
Diagnostic criteria for severe dengue: any of the following
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
Severe dengue (5% of patients)
- 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
Dengue bloods
- Thrombocytopaenia and Leukopaenia
- Prolonged APTT and PT
- Deranged U&E’s
- Elevated LFT’s especially ASR
37
Dengue investigations
- 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
Diagnosing dengue: 5 days or less post fever
- PCR: viral RNA
- PCR: viral antigen (NS1)
39
Diagnosing dengue (5 days or more post fever onset)
- 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
Management for dengue fever
- 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
Preventative measures for dengue fever
- PPE
- DEET: long sleeved clothing
- Vaccine: can precipitate severe cases of dengue if previously immunised
42
Complications of dengue
- Severe dengue: multi-organ involvement, haemorrhage and shock. 50% mortality if untreated
- Hepatic failure
- Encephalopathy
- Myocarditis
- Disseminated intravascular coagulation
- Septicaemia
43
Rickettsia
- 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
Riskettsia epidemiology
- 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
Rickettsia clinical features
- 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
Rickettsia clinical manifestations with timings
- 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
Eschar
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
Rickettsia: Laboratory examination
- 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
Treatment: Rickettsia disease
- 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
Risk factors and protective for malaria
Risk factors for malaria mortality: Pregnancy, neonatal, Sub-Saharan Africa
Protective for malaria: long sleeves, insecticide coated bed net, insect repellent
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