• mechanism of transmission
  • mosquito
  • can also be via blood transfusion, organ transplantation, transplacentally
• reservoir- birds
• classification- flavivirus

• elderly
• immunocompromise
• deletion in CCR5 gene

• most infections are asymptomatic
• some get west nile fever
• rarely, get west nile neuroinvasive disease
  • encephalitis
  • meningitis
  • polio like flaccid paralysis

• abrupt onset of fever, headache, fatigue, myalgias
  • neck pain and stiffness
• nausea, vomitting, abdominal pain
• rash sometimes (more so on trunk than extremities)
  • maculopapular

Usually recover without sequelae (3-6 days), but post fatigue illness can last weeks to months

• WNF + meningitis
• some have cranial nerve palsies
• prognosis- usually recover without permenant neurological sequelae
• dx- CSF with WBC's (often neutrophils)

• risk factors- older, immunocompromised
• chronic neurologic sequalae
  • movement disorders/extrapyramidal findings
    • tremors
    • Parkinsonism
    • ataxia
  • last months/yrs
  • high rate of institutionalization
• prognosis: 20% of people die
  • cardiac arrhythmias and respiratory failure
  • usually need hospitalizations

• usually assymetrical
• rarely occurs without fever or other manifestations of west nile disease
• prognosis- permanent weakness or prolonged recovery common

• IgM in CSF or blood
• WNND: CSF IgM most sensitive (doesn't cross the BBB)
  • usually detect by onset of CNS symptoms
  • may be detectable for up to 1 yr post infection
• WNF: serum IgM may appear 8 days after onset
• paired acute/convalescent IgG: 4x rise
• PCR: serum or CSF (poor sensitivity)

• supportive
  • fluids
  • respiratory support

• asymptomatic
• undifferentiated fever
• dengue fever syndrome
• dengue hemorrhagic fever
• dengue shock syndrome

• usually young children with first episode
• symptoms- mild febrile illness
• prognosis- unremarkable recovery (do not meet criterial for dengue fever)

• usually older children, adults
• criteria
  • 2-7 days of fever
  • more than 2 of following
    • severe headache
    • retro orbital pain
    • myalgias
    • arthralgias
    • diffuse erythematous maculopapular rash
    • mild hemorrhagic manifestations
  • NO plasma leak or severe hemorrhage

• fever
• hemorragic manifestations or positive tourniquet test
  • nasal blled
  • GI bleed
  • increase mentstrual flow
• thrombocytopenia
• plasma leakage
  • hemoconcentration
  • ascities
  • hypoproteinemia
  • pleural effusion

• abdominal pain/tenderness
• persistent vomitting
• lethargy/restlessness
• hepatomegaly
• fluid accumulation (pleural effusion, ascities)
• mucosal bleeding
• sudden increase in hematocrit with rapid increase in platelet count

• DHF plus circulatory failure
  • narrow pulse pressure (less than 20)
  • hypotension with cold, clamy skin

High mortality if not treated promptly (low mortality with intensive supportive therapy)

• clinical: tourniquet test
• acute phase: virus detection
  • blood, CSF, tissue
  • 0-5 days post onset of symptoms
  • RT-PCR
  • Ag detection (NS1 protein)
• serology: IgM capture ELISA
  IgG: paire acute/convalescence

• inflate bp cuff between cystolic and diastolic
• leave it for 5 minutes
• should see petechial rashes (more than 20 petechiae per square inch)

• mostly supportive
• early recognition of DHF/DSS and anticipatory tx
  • volume replacement key if plasma leak
  • blood and blood product transfusion as necessary (platelets are low)
• be careful to modify replacement when signs of convalescent period appear
  • otherwise, can have fluid overload

• fever last 3-4 days, than resolve (viremia clears, Ab appears)
• leukopenia
• viremic during this time
• Faget's sign- relative bradycardia
• extreme myalgias in pack
• conjunctival suffusion (hyperemia)

• called biphasic disease
• symptoms
  • fever, hepatitis/jaundice, renal failure
  • severe hemorraging
    • hematemesis
    • melena
    • bleeding from eyes, nose, bladder, rectum
• severity correlates with elevation in heaptic transaminases
• death can happen due to multiorgan failure and prolonged shock
• if you recover, life long immunty

• dx- serology IgM detectable while symptomatic (cross reactive with other flaviruses)
• tx- supportive
• prevention- live attenuated single dose vaccine
  • 10+ yrs protection
  • immunization of 80% of population necessary to prevent endemics
  • required for travel to much of Africa, pts of South America

• febrile phase (similar to regular DF)
  • potential hepatosplenomegally late
• cirtical (plasma leak) phase
  • usually alert and luccid
  • lasts 24-36 hrs
• convalescent (reabsorption) phase
  • end of plasma leak
  • stabilization of vital signs, hematocrit, increased urine output
  • rash- confluent pruritic rash with small islands of unaffected skin
  • fluid overload if don't decrease fluid resuscitation