Microbiology - Endy - Arboviruses

Question 1

What is the reservoir and vector of Eastern Equine Encephalitis?

Answer 1

Bird reservoir
Mosquito vector
Horse and human - incidental (dead end) host
virus

Question 2

What are the symptoms of EEE?

Answer 2

Clinical manifestations vary from an inapparent to influenza like illness to the syndrome of encephalitis.

fever, headache, mental status changes and neck stiffness;
CBC demonstrated a leukopenia.
CSF: WBC 120 (90% lymphocytes), Protein 100 (high), Glucose of 30 (low)

*same symptoms as Japanese encephalitis–travel history a must

Probability of developing encephalitis varies widely: highest for the EEE and lowest for VEE.

Question 3

What kind of virus is EEE?

Answer 3

EEE is in the Togaviridae family in the genera alphavirus. Positive ssRNA enveloped viruses

Alphavirus genus contains 4 encephalitic viruses which produce encephalitis; EEE, WEE, VEE and Everglades.

Focal epidemics of EEE have occurred in the Eastern USA, WEE is endemic in the Western USA, VEE is endemic in South America and N. America.

Question 4

What kind of virus is Japanese encephalitis?

Answer 4

Family Flaviviridiae, positive sense single-stranded RNA

JEV circulates as a single serotype (Vaccine efficacy ramifications)

Question 5

What is the natural host of Japanese encephalitis?

Answer 5

Pig, some birds

Humans and horses are accidental hosts

Question 6

What are the symptoms of Japanese encephalitis?

Answer 6

Incubation period 6 to 16 days

Spectrum: Febrile headache → Aseptic meningitis → Encephalitis (

Question 7

What kind of adverse reactions have occurred with the yellow fever vaccine?

Answer 7

Yellow fever vaccine–associated viscerotropic disease (YEL-AVD)- febrile illness that begins 3–5 days after vaccination and clinically resembles naturally acquired yellow fever.

Question 8

What virus causes yellow fever?

Answer 8

Family Flaviviridiae, genus Flavivirus

Question 9

What are the clinical features of the acute period of yellow fever?

Answer 9

Incubation period ranges from 3 to 6 days.

The clinical spectrum can manifest as a mild, nonspecific, febrile illness to a fulminating, sometimes fatal hemorrhagic disease.

Severe YF begins acutely with fever, chills, severe headache, lumbosacral pain, generalized myalgia, anorexia, nausea and vomiting, and minor gingival hemorrhages or epistaxes.

Bradycardia may be present despite a rising temperature (Faget’s sign).

Symptoms may last for 3 days and period of viremia.

Question 10

What are the clinical features of the hemorrhagic period of yellow fever?

Answer 10

Hemorrhagic phase is manifested by “coffee-ground” hematemesis (vomito negro), melena, metorrhagia, petechiae, and ecchymoses.

Volume depletion is secondary to vomiting and plasma leakage.

Renal failure is manifested by an increase in albuminuria and diminishing urine output.

Death (in 20% to 50% of severe cases) occurs on the 7th to 10th day of illness and is preceded by deepening jaundice, hemorrhages, rising pulse, hypotension, oliguria, and azotemia (elevated BUN).

Hypothermia, agitated delirium, intractable hiccups, hypoglycemia, stupor, and coma are terminal signs.

Laboratory findings: leukopenia, elevation of bilirubin, serum transaminase levels, thrombocytopenia, prolonged PT and PTT, and ST-T wave changes in the electrocardiogram.

Question 11

What virus causes dengue fever?

Answer 11

Genus Flavivirus & Family Flaviviridae
Four serotypes
DEN-1, -2, -3, and -4

Question 12

What are the symptoms of dengue fever?

Answer 12

After a 2- to 7-day incubation period, high fever, headache, retrobulbar pain, lumbosacral aching pain, conjunctival congestion, and facial flushing develops.

Fever lasts for 6 to 7 days with generalized myalgia, bone pain, anorexia, nausea, vomiting, weakness, and prostration.

A generalized macular rash may appear on the first or second day. Following defervescence (day 3 to 5) a secondary rash, maculopapular or morbilliform appears on the trunk and then spreads centripetally to the face and limbs but spares the soles and palms..

Fever may rise again, creating the second phase of the saddle-back course.

The peripheral WBC count is depressed with an absolute granulocytopenia, and the platelet count may fall to less than 100,000/mm3.

Question 13

Secondary/hemorrhagic dengue is characterized by:

Answer 13

Hemorrhagic manifestations include petechiae, epistaxis, intestinal bleeding, menorrhagia, and a positive tourniquet test.

Myocarditis may occur and neurologic disorders (encephalopathy, peripheral mononeuropathy, polyneuritis, and Bell’s palsy). Reye’s syndrome has also been reported to follow dengue infection.

Prolonged convalescence may occur with generalized weakness, depression, bradycardia, and ventricular extrasystoles.

Question 14

Petechiae in a person with viral symptoms would suggest what diagnosis?

Answer 14

Dengue hemorrhagic fever (DHF)

Question 15

____ is the most common arbovirus causing human infection in the subtropical and tropical regions of the world.

Answer 15

Dengue is the most common arbovirus causing human infection in the subtropical and tropical regions of the world.

Question 16

Arbovirsus cause 4 clinical syndromes. What are they?

Answer 16

1. Systemic febrile illness (ie Chikungunya, O’nyong-nyong, Ross River, Dengue);
2. Fever with arthritis (Chikungunya, Ross River, O’nyong-nyong
3. Encephalitis (Japanese encephalitis, West Nile Virus, Venezualan EE, EEE, WEE, Murray Valley E)
4. Hemorrhagic Fever (Yellow fever, Dengue, Rift Valley Fever, Chikungunya)

Question 17

In what places is the incidence of Japanese Encephalitis increasing?

Answer 17

India and Nepal

high mortality and morbidity

Question 18

What arbovirus has the highest incidence of developing encephalitis?

Answer 18

EEE

Lowest for Venezualen EE

Question 19

64 year old white male who presents in August with fever, headache (worse hes had in his life), mental status changes (forgetfulness) and neck stiffness. No travel in the preceding year outside of NY State.
Lives in Cicero, NY with a house bordering on Cicero Swamp. CBC demonstrated a leukopenia.
CSF: WBC 120 (high) (90% lymphocytes), Protein 100 (high), Glucose of 30 (low).

What does he have?

West Nile Encephalitis
St. Louis Encephalitis
Powassan encephalitis
Eastern equine encephalitis
None of the above.

Answer 19

Eastern equine encephalitis - key is that EEE is endemic to Cicero swamp

Others could all be possible and share similar symptoms - Critical take away is that knowing the geography and history of travel is essential to identifying correct diagnosis

Not St. Louis powassan or West Nile b/c of location - but all present with similar symptoms

Powassan is tickborne other are mosquito vectors

Question 20

What are the most rapidly lethal type of arboviruses?

Answer 20

Those that cause hemmoragic fever

Yellow fever
Dengue
Rift valley fever
Chikungunya

Question 21

What is a dead end host?

Answer 21

An organism that once gets infection doesn’t propagate it

Question 22

What type of viruses cause Eastern Equine Encephalitis , Western Equine Encephalitis, Venezuelan Equine Encephalitis, and Everglades Encephalitis?

Which is more likely to contract in US?

Wich have greater mortality?

What is Vector? Reservoir?

What is the treatment?

Answer 22

Alphaviruses: +ssRNA, enveloped

Likelyhood of contracting: EEE>WEE
Mortality: EEE>VEE>WEE

Most infections do not manifest in encephalitis (more common are flu-like symptoms) but still detectable from blood work

Mosquito - Culista melanura
Reservoir - Birds

Supportive care - No cure

Question 23

What are signs of encephalitis?

Answer 23

fever
headache (worse in life)
mental status changes (forgetfulness)
neck stiffness

Question 24

64 year old white male who presents in March with fever, headache, mental status changes and neck stiffness. Patient had traveled to Thailand 2 weeks before his illness. Lives in Cicero, NY with a house bordering on Cicero Swamp. WBC 120 (high) (90% lymphocytes), Protein 100 (high), Glucose of 30 (low).

What does he have?

West Nile Encephalitis
Japanese Encephalitis
Powassan encephalitis
Eastern equine encephalitis
None of the above.

Answer 24

Japanese Encephalitis - travel history

Question 25

What type of virus causes Japanese encephalitis? What is the nucleic acid? What is the vector? Host? What is special about the host? When is the most likely time of day to become infected? What locations are high infections sites? What time of year can you be infected?

Answer 25

Flavivirus (type of arbovirus)
+ssRNS (Single serotype but 5 genotypes endemic to diff parts of SE Asia)
Mosquito - Culex
Natural host is Pig - can sustain high viral loads without becoming infected
Humans are accidental hosts
Night time because Culex is a night feeder
Rice fields, marshes
Year round transmission due to agricultural irrigation but rainy seasons have highest transmission rates

Question 26

Why is JEV considered a preventable disease?

Answer 26

2 Vaccines available (single serotype virus makes it amenable to vaccination)

JE-Vax - discontinued production due to anaphylaxis reaction

IXIARO - contains purified and inactivated JEV virus - protamine sulfate clears DNA and contaminants - formaldyhyde inactivates virus

Question 27

What are the two presentation of yellow fever?

Answer 27

Visotropic - high mortality >60% a febrile illness that begins 3–5 days after vaccination and clinically resembles naturally acquired yellow fever.

Neurotropic - encephalitis

Question 28

How is Yellow fever transmitted?

Answer 28

nonhuman primates to mosquitoes to humans

Jungle cycle of monkey to mosquito to monkey is reservoir

Question 29

What is Faget’s sign? What disease is it seen in?

Answer 29

Bradycardia despite high temp - acute phase of yellow fever

Question 30

Where is yellow fever found?

Answer 30

Equitorial parts of south america and Africa

Question 31

Can you get Dengee fever in the US?

Answer 31

Yes - Key west

Question 32

Clinical presentation of Dengue

What is the most serious pathology?

Answer 32

Hemorrhagic disease!

Petechia on chest wall or subcutaneous hemorrhage or hemorrhage into stomach.

Can develop shock syndrome - intravascular volume depletion from plasma leakage into lung causing pleural effusion or from hemorrhagic blood loss - can lead to cardiovascular collapse

Hematocrit increase is indication of plasma leakage into lung because RBS become concentrated with less plasma

Question 33

What is the most common arboviral infection in the subtropical and tropical regions of the world?

Answer 33

Dengue mother fucker!

Question 34

1. True or False: Arboviruses are viruses that are transmitted by rodents that breed in forests
   (arboretum) and named from the combination of arboretum and virus (arbovirus).

Answer 34

1. • F

Question 35

Which are the following clinical syndromes are produced by the arboviruses?

a. Systemic febrile illness.
b. Fever with arthritis.
c. Encephalitis.
d. Hemorrhagic fever.
e. All of the above.

Answer 35

2. • E

Question 36

Which are the following statements are true about Japanese encephalitis virus?

a. It is a minor cause of encephalitis in Asia.
b. The life cycle involves birds, mosquitoes, pigs and humans are a dead-end host.
c. There is no licensed vaccine available for protection.
d. Infection in the brain is mild and not severe.
e. None of the above.

Answer 36

3. • B

Question 37

Which are the following statements are true about Dengue virus?

a. It is a minor cause of infection in the world.
b. The life cycle involves birds, mosquitoes, pigs and humans are a dead-end host.
c. There is a licensed vaccine available for protection.
d. Infection can result in a febrile illness to a severe hemorrhagic form.
e. None of the above.

Answer 37

4. • D