Arboviral Diseases

Question 1

Nearly all arboviruses have ___________ genomes.

Answer 1

RNA

Question 2

In most cases, humans are just _______________. What are three exceptions?

Answer 2

dead-end hosts for arboviruses

These four viruses are human-mosquito-human: 
•Dengue
• Yellow fever
•Zika virus 
• Chikungunya

Question 3

True or false: once a mosquito has bitten an infected vertebrate, it is immediately infectious for humans.

Answer 3

False. The virus has to replicate and produce systemic viremia in a mosquito in order to become infectious for humans. This usually takes 8 - 12 days.

Question 4

Most arboviral infections are _____________.

Answer 4

asymptomatic

Question 5

Three virus families encompass almost all the human arboviruses: _________________.

Answer 5

Togaviridae (Western, Eastern, and Venezuelan encephalitis); Flavivirus (West Nile, yellow fever, and dengue); and Bunyavirus (California encephalitis and Rift Valley fever)

Question 6

Discuss the three types of dengue disease.

Answer 6

• Dengue fever: a mild febrile illness with myalgias, arthralgias, and rash
• Dengue hemorrhagic fever: fever with shock, capillary leak, and DIC
• Asymptomatic infection

Question 7

What are warning signs that dengue may be progressing?

Answer 7

• Abdominal pain
• Vomiting
• Mucosal bleeding
• Any sign of organ failure (e.g., elevated AST/ALT)

Question 8

How common is dengue?

Answer 8

There are about 400 million infections per year, of which only 25% are symptomatic.

Question 9

Where is dengue virus found?

Answer 9

All around the world in tropical/equatorial areas

Question 10

What is unique about the dengue reservoir?

Answer 10

It is a human-mosquito-human cycle, whereas most other arboviruses have a non-human animal host.

Question 11

______________ is required for dengue hemorrhagic fever.

Answer 11

Two heterologous dengue strains (e.g., DENV-1 and DENV-2)

Question 12

What is the leading hypothesis as to why a second dengue infection is worse?

Answer 12

During the initial infection, antibody is generated to virions. During the subsequent infection, those antibodies bind virions and get phagocytosed, which enhances infectivity if the antibodies have declined to a sub-neutralizing level.

Question 13

Currently, a vaccine to ________________ is in trials.

Answer 13

dengue (phase III, 60% efficacy thus far for dengue fever and 90% for DHF)

Question 14

What are the three stages of Chikungunya virus?

Answer 14

• 1 (up to 3 weeks): fever and arthralgia
• 2 (3 weeks to 3 months): continued joint pain
• 3: musculoskeletal disorders

Question 15

True or false: Chikungunya is in the Flavivirus family.

Answer 15

False. It is in the Togaviridae family.

Question 16

Although most Zika virus infections are asymptomatic, 20% of people infect develop _______________.

Answer 16

arthritis, fever, myalgias, and conjunctivitis

Question 17

ZIka is a member of the ___________ family.

Answer 17

Flavivirus

Question 18

The main reservoir for West Nile Virus is ____________.

Answer 18

birds

Question 19

West Nile encephalitis is more common in _____________.

Answer 19

the elderly

Question 20

West Nile virus is most often asymptomatic (80%), but it can cause ______________.

Answer 20

fever and myalgia (20%) and encephalitis (1%)

Question 21

Which virus family is Japanese encephalitis in?

Answer 21

Flavivirus (hosts are birds and pigs)

Question 22

Japanese encephalitis can cause _____________.

Answer 22

encephalitis and aseptic meningitis

Question 23

Like most of the viruses we’ve talked about – with the notable exception of influenza –the majority of West Nile virus cases are _______________.

Answer 23

asymptomatic

Question 24

St. Louis encephalitis virus is in the ___________ family.

Answer 24

Flaviviridae

Question 25

Colorado tick fever is transmitted by the ___________ tick.

Answer 25

Dermacentor

Question 26

Which two Flaviviruses have vaccines?

Answer 26

Yellow fever and Japanese encephalitis