Murray Valley Encephalitis Virus Flashcards
What is your opening line for MVEV?
MVEV is a non-vaccine-preventable, nationally notifiable flavivirus disease similar to JEV, West Nile/Kunjin. Most cases are asymptomatic but encephalitis can occur. High-risk groups for infection include those working or recreating in endemic areas of high mosquito burden. Children and adults > 50 are at higher risk for severe disease. Epidemics can occur after periods of significant rainfall / flooding.
Is MVEV nationally notifiable?
Yes. Urgent.
(Labs and doctors)
Which virus family does MVEV belong to?
Flavivirus
How is MVEV transmitted?
Mosquito - main vector Culex annulirostris (widespread inland pest).
Which animals are the primary hosts for MVEV?
Waterbirds (main transmission cycle)
Marsupials and livestock may be infected but role in transmission unclear.
True or False: humans are dead end hosts of MVEV?
True - do not achieve sufficient viraemia for ongoing transmission.
What are the clinical features of MVEV?
- Often asymptomatic or mild disease (fever, headache, N/V).
- Meningitis/encephalitis in < 1% of cases (higher in children) – seizures, ataxia, drowsiness, confusion.
- CFR 15-30%, neurological sequelae 30-50% survivors.
Which groups are at high risk of MVEV infection?
High mosquito exposure (outdoor activity near breeding grounds).
Which groups are at higher risk of severe disease from MVEV?
Children, adults > 50yo have worse outcomes.
What is the definition of a confirmed case of MVEV?
Clinical
AND
Lab (isolation / detection / seroconversion / IgM in absence of other flaviviruses
What is the definition of a probable case of MVEV?
Laboratory suggestive
AND
Clinical
How is MVEV diagnosed?
PCR (blood/CSF)
Serology (acute + convalescent)
VIDRL ref lab.
What is the incubation period for MVEV?
5 - 28 days
(usually 7-12 days)
Tip: 1 - 4 weeks
What is the infectious period for MVEV?
N/A as no person-to-person transmission.
What is the outbreak definition of MVEV?
Outside enzootic regions, 1 case is an outbreak
Epidemiology: where and when was MVEV first detected?
Vic/NSW/SA in 1951
Also found in PNG and Indonesia
Epidemiology: where have most cases of MVEV been detected in Australia?
Northern and central Australia
Epidemiology: in which years were there significant outbreaks of MVEV?
2013: 16 cases (9 in WA)
2023: 26 cases (6 each in Vic/WA/NSW)
Epidemiology: where is MVEV considered enzootic?
NT / Northern WA
Enzootic - constantly present in a particular animal population within a specific geographic area
Epidemiology: where is MVEV considered epizootic?
South-East Australia.
Rare activity but potential for large outbreaks usually after significant rain / flooding e.g. 2023
Epidemiology: when to MVEV epidemics / outbreaks occur?
Usually after significant rainfall / flooding.
How is MVEV prevented?
- Standard prevention measures for VBDs
- Surveillance - mosquitoes, chickens, humans, climate / weather events
Surveillance signals - high vector numbers, MVEV detection in mosquitoes, recent seroconversion in animals, human cases
What resources are available for public health response?
- SoNG.
- DoH Protocol
- Framework for surveillance, prevention and control of MVEV in Australia (NAMAC)
How are cases of MVEV managed?
Depends if enzootic / epizootic.
If epizootic, investigation, intervention / alert is required to reduce ongoing risk.
Interview - DRSVECTA
Treatment - supportive
Isolation / exclusion - N/A
Education - sx, transmission
Active case-finding - clinician alerts (encephalitis, febrile illness)
