Arboviruses Flashcards
In the US, what is the major spreading cycle of Arboviral
From mosquitos to birds to mosquitos to birds
In regards to Arboviral, infections of humans are considered _______
incidental
-Humans are a ‘dead-end-host’
-This is b/c humans can’t spread the disease back to a mosquito or other people
-This is NOT an urban cycle, no matter the number of infected birds or humans
What is the urban cycle of spread of Arboviral
-From human to mosquito to human to mosquito
-In this type of spread, the infection is not circulating through a different animal and several things must be in place to spread the disease
What is needed for an urban cycle of spread?
-The virus has to be able to infect urban mosquitos
-There has to be high enough virus levels in the infected person’s blood to infect a mosquito
-There must be high enough levels of mosquitos to sustain the spread of the disease
-There has to be high enough density of people susceptible to infection
So far, which 4 different arboviruses have high enough virus levels in a person’s blood to infect a mosquito?
Yellow fever
Dengue
Zika
Chikungunya
Describe the general characteristics of West Nile Virus
West Nile Virus is a Flavivirus, +ssRNA, enveloped virus
Which arbovirus has the most cases in the US?
West Nile Virus
Is West Nile Virus (asymptomatic/symptomatic)?
Asymptomatic
How is West Nile Virus transmitted?
-It is NOT transmitted through urban spread
-The mosquito vector is not the same vector that spread Zika, dengue, and chikunguna.
-The vector for West Nile Virus (WNV) prefers to feed on birds and bites mostly from dust to dawn
What age group is affected by West Nile Virus?
It can occur at any age
What are the post-infection symptoms of Wet Nile Virus?
Many can have lingering problems with fatigue (some also report motor defects)
The older you are, the more likely you will get the _________ form of WNV
neuroinvasive
Of those infected with neuroinvasive WNV, about 50% have _________ and recover completely
meningitis
The remaining 50% of those infected with neuroinvasive WNV have more serious complications like….
-Encephalitis and/or acute flaccid paralysis
-This is where the deaths more likely to occur
-Survivors can have long-term complications like memory loss, muscle weakness, fatigue, and difficulty doing daily activities
Describe the structure of Yellow Fever
Yellow Fever is a Flavivirus, +ssRNA, enveloped virus
What type of vaccine is the yellow fever vaccine?
An attenuated-live vaccine that, with just one shot, gives 99% protection for life
Which is the first arbovirus known to have an urban cycle?
Yellow Fever
Several countries in __________ are endemic for Yellow Fever
Africa and South America
Half of the yellow fever infections are asymptomatic; describe the symptoms of the other 50% of infections
-Some will have severe disease
-About 1/2 of them will die
-Jaundice is a common complication of severe disease, hence yellow fever and hemorrhaging
How does Yellow Fever spread?
-By the same mosquito that spreads Zika, dengue, and chikungunya.
-For this reason, if you live in an area endemic for yellow fever, most countries require proof of vaccination before entry
What is the number one arbovirus worldwide?
Dengue
How many serotypes does dengue have?
4
What happens the first time you are infected with dengue?
You usually don’t get the severe form of dengue disease
What type of virus is Dengue?
Another Flavivirus with a high number of asympotomatic infections
If you are infected again with a different serotype of dengue, now you are at risk of ______
More severe disease, Dengue Hemorrhagic Fever or Dengue Shock
-Death from more severe forma is much more likely without tx
T/F: In most endemic areas, several dengue serotypes circulate at the same time
True
Let’s say you are infected with Dengue serotype 1 and recover. What do you have now?
Lifelong immunity to serotype 1 but not any other dengue type
If now you are infected with a different serotype, like 3, what happens to the antibodies from type 1?
The antibodies to type 1 will bind to the type 3 viruses from the new infection
Instead of neutralizing the type 3 viruses, the bound antibody is recognized by _________ on monocytes, and the type 3 receptor is internalized into the monocyte. What does this aid in?
the Fc receptor;
This aids the virus in infecting the monocyte leading to more efficient infection, high viral loads, and more severe disease
Why has it been so hard to make a vaccine for dengue?
Because of the fact that antibodies to one serotype can aid in the infection of another serotype and lead to more severe diseases
-The fear was that the vaccine would lead to more dengue hemorrhagic fever/dengue shock, not stop it
_____ has symptoms similar to dengue, with most asymptomatic
Zika
What type of virus is Zika?
Flavivirus
Problems associated with Zika are ___________ and congenital abnormalities.
Guillian-Barre Syndrome
(Zika is rarely fatal)
What are the symptoms of Zika?
Fever
Rash
Joint pain
Conjunctivitis
What has Zika virus been linked to?
Congenital abnormalities
The same risk for congenital Zika syndrome if the maternal infection is _________
symptomatic or asymptomatic
When is there a risk for congenital Zika syndrome during pregnancy?
During any trimester of maternal infection
What can Zika virus affect in a fetus?
Can affect brain development in the fetus, leading to microcephaly, damage to the brain, slight and hearing problems, and movements of limbs
How can Zika be spread?
Through sexual contact from both symptomatically and asymptomatically infected people
What type of virus is Chikungunya?
A togavirus
How is Chikungunya spread?
-By the same mosquitos that spread yellow fever, dengue, and Zika
-It also has an urban cycle of spread
What happens to most people who get infected with Chikungunya?
-Most people DO get sick
(Relatively few are asymptomatically infected)
What are the symptoms of chikungunya?
The symptoms overlap with dengue and zika, but there is much more severe joint pain
What is the problem with Chikungunya infection?
That about 1/4 of infected people will have lingering joint pain for months to years
What is the vaccine for Chikungunya?
There is no vaccine, but infection can afford lifelong protection from reinfection
All of the arboviruses are _____________ infections
systemic/generalized
