Arbo-Viruses

Question 2

West Nile virus is an _____ virus transmitted by _____.

Answer 2

encephalitic; mosquitos

Question 3

Dengue is a ______ ______ virus transmitted by _____.

Answer 3

hemorrhagic fever; mosquitos

Question 4

Describe the mosquito life cycle.

Answer 4

Adults lay eggs on water, develop into larvae and then pupae while in water, adult emerges from surface to be airborne

Question 5

Adult female mosquitos live for ____ weeks, typically feed every ____ days, and lay eggs _____ days after each blood meal.

Answer 5

2-5 weeks; 3-5 days; 2-3 days

Question 6

Name 3 viral vector-borne diseases found in NC (all are transmitted by mosquitos).

Answer 6

West Nile Encephalitis, Eastern Equine Encephalitis, LaCrosse Encephalitis.

Question 7

Which age group is most at risk for viral vector-borne disease?

Answer 7

likelihood increases with age

Question 8

Flaviviruses encode 3 proteins. What do they do?

Answer 8

C protein= nucleocapsid structure; E protein= receptor binding and fusion; M= assembly and release

Question 9

Which viral protein is targeted for flavivirus vaccines?

Answer 9

E protein

Question 10

Why are the number of cases of dengue rising so much?

Answer 10

globalization, population growth, urbanization, travel

Question 11

what portion of dengue virus infections are symptomatic?

Answer 11

only 1/3, and still only some have hemorrhagic fever

Question 12

risk factors for symptomatic/severe dengue infection

Answer 12

age, genetic background (Africans more protected), previous dengue infection with alternate serotype dramatically increases risk of severe response (7x more likely), maternal antibody passed to infant

Question 13

antibody enhanced dengue disease

Answer 13

maternal antibody initially protects infant for first 2 months, after which time the lower concentration of maternal antibody is insufficient to protect, and actually enhances risk of DHF/DSS peaking at age 8mo

Question 14

how do low levels of antibodies enhance dengue disease?

Answer 14

Antibody on macrophage is used as a receptor for the virus to infect cells, resulting in release of cytokines and inflammation (severe ds)

Question 15

what is the traditional reservoir for West Nile virus?

Answer 15

BIRDS

Question 16

how do humans get infected with West Nile?

Answer 16

incidental infection, we are a dead-end host (can be transplacental, by lactation, organ transplant)

Question 17

clinical manifestations of West Nile

Answer 17

80% asymptomatic, 20% mild fever and trunkal rash, less than 1% neuroinvasive disease (encephalitis or aseptic meningitis)

Question 18

at what time of year do we see West Nile outbreaks?

Answer 18

late summer/early fall, peaking in August

Question 19

West Nile pathogenesis

Answer 19

skin ? langerhans cells ? LNs ? viremia, organs (causes fever, GI symptoms)

Question 20

What is the downside to PCR for detection of flaviviruses?

Answer 20

viremia is transient, very small window to detect virus in blood

Question 21

Why is serology an imperfect diagnostic tool for flaviviruses like dengue and West Nile?

Answer 21

confounded by cross reactivity b/w various flaviviruses (ELISA is still the predominent test for WNV)

Question 22

What is the most recent and effective way to detect dengue?

Answer 22

NS1 antigen detection test; still being evaluated

Question 23

How do we prevent, control, and treat flaviviruses?

Answer 23

Prevent by mosquito control, good prospect for vaccine devt. Therapy is only supportive (no antivirals).