Case 12: Influenza, dengue Flashcards
Position for LP
- 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
LP appearance
- Normal - clear (‘gin-coloured’)
- Cloudy/purulent - meningitis
- Blood-stained - subarachnoid haemorrhage, or a traumatic tap
LP opening pressure
- Normal is 8-20cm
- May be elevated due to infection, inflammation, haemorrhage and idiopathic intracranial hypertension
LP white blood cells
- Normal – 0-5 cells/ul
- ↑ neutrophils – bacterial meningitis
- ↑ lymphocytes – viral & TB meningitis/ encephalitis, (& inflammatory conditions, malignancy)
LP: protein
- Normal - 0.15-0.45 g/L
- ↑infection (TB > bacterial > viral), inflammatory conditions, Guillain-Barre syndrome
- Oligoclonal bands in multiple sclerosis
LP: glucose
- Paired with blood glucose
- Normal - 60-80% of serum glucose
- ↓ (<50%) in infection (esp. bacterial, TB and fungal)
LP gram stain
- Gram positive: Dark purple- Strep pneumoniae cocci in pairs/short chains
- Gram negative: Pink- Neisseria meningitidis diplococci
Streptococci under the microscope
- 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
Steps in identifying Streptococci: order
Microscopy → Culture and colonial appearance (Catalase) → Haemolysis → Further identification → Susceptibility testing
Culture appearance Streptococci and Catalase test
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)
Streptococcus haemolysis classification
- 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
Further identification of Streptococcus
- Not always needed but is needed in IE, used to identify the specific species
- Mass spectrometry
- Panel of biochemical reactions
Susceptibility testing
- 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
Influenza: clinical features
- fever greater than 38ºC
- myalgia
- lethargy
- headache
- rhinitis
- sore throat
- cough
- diarrhoea and vomiting
Consider prescribing anti-retroviral treatment for influenza if the following applies
- 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
Antiretrovirals for influenza
- 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
Influenza virus
- RNA virus
- Types A, B and C effect humans
- Type A has H and N subtypes
Who is offered the free flu vaccine
- Aged 65 and over
- Young children
- Pregnant women
- Chronic health conditions, such as asthma, COPD, heart failure and diabetes
- Healthcare workers and carers
Flu testing
- 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
Flu- post exposure prophylaxis criteria
- 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
Complications for influenza
- 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
Types of influenza
- Influenza A and B belong to the Orthomyxociridae virus family
- Type A influenza: most common and severe, more likely to cause pandemics
Bronchiolitis
- Fever, widespread crepitations, occasionally conjunctivitis
- RSV most common cause
- Most children have been infected by 2
- Seasonal- winter illness
- Treatment is supportive
Covid
- Diagnosed with Viral PCR
- Can be mild-severe
- Vaccinations
- Treatment with anti-virals in severe cases
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
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.
Timings of dengue fever
- 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
The three phases of dengue
- febrile phase (2-7 days): normal WBC, platelet and Haematocrit
- 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
- 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
Diagnostic criteria for probable dengue
- live in or travel to endemic area
- fever
- two of: N/V, rash, aches and pains, positive torniquet test, leukopenia or any warning sign
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
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.
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
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
Diagnostic criteria for severe dengue: any of the following
- severe plasma leakage: shock (dengue shock syndrome), fluid accumulation with respiratory distress
- severe haemorrhage
- severe organ impairment: Liver AST/ALT above 100 (AST or ALT >1000), CNS impaired consciousness, heart failure
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
Dengue bloods
- Thrombocytopaenia and Leukopaenia
- Prolonged APTT and PT
- Deranged U&E’s
- Elevated LFT’s especially ASR
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
Diagnosing dengue: 5 days or less post fever
- PCR: viral RNA
- PCR: viral antigen (NS1)
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)
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
Preventative measures for dengue fever
- PPE
- DEET: long sleeved clothing
- Vaccine: can precipitate severe cases of dengue if previously immunised
Complications of dengue
- Severe dengue: multi-organ involvement, haemorrhage and shock. 50% mortality if untreated
- Hepatic failure
- Encephalopathy
- Myocarditis
- Disseminated intravascular coagulation
- Septicaemia
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
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
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
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
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.
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
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
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
