Arboviruses Flashcards
Classification of West Nile Virus
Flavivirus
When was it first discovered in N. America and when does it seasonally peak
1999 discovered AND peaks usually in late summer/fall each year
What are the vectors and hosts for WNV
culex mosquitos and many types of birds.
How has transmission occurred?
Usually arthropod although some human-to-human via blood transfusions, organ transplants, transplacental psread, breast milk, and sometimes… percutaneous occupational exposure.
What % of WNV infections are asymptomatic?
75% are asymptomatic
What % of infections lead to neuroinvasive disease
1%
Describe the clinical sx of WNV
- fever
- headache
- backache muscle aches
- vomiting (may lead to dehydration)
- diarrhea
- loss of appetite
Transient macular rash may occur
This is called West Nile Fever. Often followed by persistent fatigue
How long does this West Nile Fever usually last
3-6 days
What is the outcome of neuroinvasive diasease
meningitis, encephalitis, polio-like paralysis… death
Who is at risk
the elderly (>50), immunodeficiency. 10% mortality
How do you dx WNV
IgM detection in serum for acute disease. retrospectively by looking for >4x increase in IgG
Prevention of WNV?
draining water
Classification of Eastern Equine Encephalitis? How many cases each year in US
alphavirus - single stranded RNA. only 5-15
Who is at risk of EEE? death rate? Long-term
young children and elderly. 50-70% death rate. Long-term = seizures, spastic paralysis, personality changes, and mental retardation
What makes it different from WNV?
transmitted by a different mosquito species AND is maintained in birds in the fresh water swamps of gulf of mexico and atlantic states
Where is Western Equine Encephalitis found and classification
alphavirus. Found in Western plains of the US, canada, and South America. Similar to EEEV, BUT it only causes CFR of 3-10%
Distribution and classification of St. Louis Encephalitis
flavivirus, distributed throughout western hermisphere
Mosquito vector
culex mosquito… just like WNV
At risk AND CFR?
persons >60 are at risk. CFR is 22%
Classification of Dengue? # of serotypes?
Also a flavivirus. there are 4 serotypes - each provide specific lifetime immunity and short-term cross-immunity
How many infections occur each year? how many are hemorrhagic
Dengue is the most common arbovirus in the world with 100 million infections annually. about 500,000 are hemorrhagic
Describe pathogenesis of dengue.
DENV will replicate locally and in lymph nodes. Within 2-3 days it will spread to the blodo and makes its way to various tissues including the skin.
When do sx start?
2-3 days after infection correlating with viremia, replication in certain tissues (like muscle), and cytokine release
What is dengue shock syndrome (DSS)?
After sudden extravasation of plasma into the extravascular sites including the pleural and abdominal cavities. This leads to intense immune activation and formation of immune complexes that will activate complement.
Who is at risk of DSS
those with pre-existing partial anti-dengue immunity. Heterologous antibodies may enhance viral uptake and replication. This is called ANTIBODY-DEPENDENT ENHANCEMENT.
What is the dengue vector. What time do they bite?
Aedes aegypti mosquito. Female. daytime feeders
What are the 4 fates of dengue clinically?
- Undifferentiated fever (most common manifestation)
- classic dengue fever
- dengue hemorrhagic fever
- dengue shock syndrome
What is dengue fever?
fever, headache, muscle and joint pain (“break bone fever”), nausea/vomiting
What are the hemorrhagic manifestations?
skin hemorrhages (petechiae), gum bleeding, nasal bleeding, gastro-intestinal bleeding, hematuria (blood in urine), increased menstrual flow
What are labs associated with dengue hemorrhagic fever?
1. low platelet count (<100,000) leaky capillaries evidence: 2. elevated hematocrit 3. low albumin 4. pleural or other effusions
What are the 4 clinical criteria for dengue shock syndrome
- rapid, weak pulse
- hypotension
- cold/clammy skin
- altered mental status
How does one lab test for dengue?
- viral detection by RNA PCR
- ELISA for nonstructural protein 1
- virus isolation
- IgM antibody test for serologic diagnosis
- 4-fold rise in IgG antibodies for chronic infections
Classification of yellow fever and where did it come from slash where is it found?
flavivirus that came from Old-World. Now it is found in tropical areas of sub-Saharan Africa and South America
What is the vector
Aedes
What are the only two major arboviruses where humans are the major vertebrate host
dengue and yellow fever
How many YF deaths per year and where?
30,000 deaths (just like dengue) and 90% in africa
how long is the incubation period
3-6 days.
Describe the unique acute period
after incubation, there are 3 days of viremia with flu-like symptoms, then there is 1 day of defervescence and improvement (24 hrs) and then it all returns with vomiting epigastric pain, prostration, jaundice.
What happens in severe disease?
It can progress to hemorrhagic phase in a minority of cases. you see the following:
petechiae, ecchymoses, melena. intravascular volume depletion. Renal failure
decreased urine output and increased albuminuria (albumin in urine)
What is the vaccine like?
95% effective. It is a live attenuated vaccine. need a new one every 10 years
What classification is chikunguya (CKV)?
alphavirus
What happened to CKV spread and what is its vector
it spread from africa to indian subcontinent and asia. What let it do this was a change that allowed it to utilize vector of A. aegypti to A. albopictus.
Describe chikunguya acute sx.
severe polyarthralgias, arthritis, rash, fever, headache, GI sx
what are hallmark lab findings
lymphopenia, hypocalcemia, thrombocytopenia
How is dx made
IgM antibody or virus detection. confirmed by IgG rise in convalescent serum
What are the long-term sequelae
arthralgias and arthritis may persist for months (70% past 2 months and 13% past 6 months)
