Arboviruses

Question 1

In Arboviruses cycle of spread, what is the major way it is done?

Answer 1

• mosquitos to birds to mosquitos to birds
• infections of humans are considered dead end host because humans can’t spread the disease back to mosquito or other people
• NOT an urban cycle

Question 2

What makes a cycle of spread “urban”?

Answer 2

• from human to mosquito to human to mosquito
• virus must be able to infect urban mosquitos
• must have high enough virus levels in the infected person’s blood to infect a mosquito
• must be high enough levels of mosquitos to sustain the spread of the disease (varies with external sources)
• must have a high enough density of people susceptible to infection

Question 3

What type of virus is West Nile?

Answer 3

• flavivirus
• +ssRNA
• enveloped

Question 4

What are some general characteristics of West Nile virus?

Answer 4

• arbovirus has most cases in US
• 80% of infection will be asymptomatic
• 1-5 thousand cases of reported symptomatic infections annually (with 4% death rate)

Question 5

What is the vector for West Nile virus?

Answer 5

• NOT the same as Zika, dengue, and chikungunya
• prefers to feed on birds and bites mostly dusk to dawn

Question 6

What makes you more susceptible to have sever complications of West Nile?

Answer 6

• 20% of people infected will get West Nile fever (occurring at any age)
• the older you are, the more likely you will get the neuroinvasive form of the virus
• of the people will the neuroinvasive form, ~50% will have meningitis and recover completely; the other 50% can have encephalitis and/or acute flaccid paralysis, and 15% of people can die (survivors have long term complications)

Question 7

What type of virus is Yellow Fever?

Answer 7

• family: flavivirus
• +ssRNA
• enveloped
• urban cycle (1st arbovirus known to have urban cycle)

Question 8

Is there a vaccine for yellow fever?

Answer 8

Yes
- live attenuated vaccine
- 99% protection for life with one shot

Question 9

T/F: Yellow fever is eradicated

Answer 9

False!
- countries in Africa and South America are endemic for Yellow Fever

Question 10

What do Yellow Fever, Zika, Dengue, and Chikungunya have in common?

Answer 10

• spread by the same mosquito
  (urban cycles of spread)

Question 11

What are the symptoms for Yellow Fever?

Answer 11

• 50% asymptomatic
• 15% of people will have severe disease (jaundice, hemorrhaging, black vomit, bleeding from eyes, nose, mouth)
• of the people with severe disease, half will die

Question 12

What is the number one arbovirus worldwide?

Answer 12

Dengue

Question 13

How many serotypes does Dengue have?

Answer 13

• 4 (1-4)
• in most endemic areas, several serotypes circulate at the same time

Question 14

How do multiple infections with Dengue work?

Answer 14

• first time infected, usually don’t get sever form of dengue
• if infected again with a different serotype, you are at risk of more severe disease such as dengue hemorrhagic fever or dengue shock
• without tx of dengue, 20% can die but with tx only 1%

Question 15

Why are infections with a different serotype of Dengue much more severe?

Answer 15

• if infected with one serotype= lifelong immunity
• if infected with a different serotype= more efficient infection, higher viral loads, more severe disease
• due to antibodies of old serotype will bind to new virus and will be internalized into the monocyte rather than neutralizing antibodies *
• makes it hard to develop a vaccine for Dengue

Question 16

What are the symptoms of Zika virus?

Answer 16

• symptoms similar to dengue but milder
• 75% asymptomatic
• symptoms: fever, rash, joint pain, and conjunctivitis
• rarely fatal

Question 17

What are some characteristic problems associated with Zika virus?

Answer 17

• Guilain-Barre Syndrome
• congenital abnormalities

Question 18

How do the congenital abnormalities work in Zika virus?

Answer 18

• same risk if mother is asymptomatic or symptomatic
• risk during any trimester of pregnancy
• can effect brain development in the fetus, leading to microcephaly, damage to brain, sight and hearing problems, problems with movement of limbs

Question 19

How can Zika virus be spread?

Answer 19

• sexual contact from both asymptomatic and symptomatic infected people

Question 20

Although Chikungunya is spread by the same mosquito as Yellow Fever, Dengue, and Zika; why is it different?

Answer 20

• Chikungunya family: togavirus while Yellow Fever, Dengue, Zika family: flavivirus
• also, most people infected with Chikungunya DO get symptoms. few are asymptomatic

Question 21

What is the problem with Chikungunya infection?

Answer 21

• similar to symptoms to Dengue and Zika but about 1/4 of infected people will have lingering joint pain for months to years

Question 22

T/F: There’s a vaccine for Chikungunya

Answer 22

False!

Question 23

What type of infection are the arboviruses?

Answer 23

systemic/generalized