#28 Flaviviruses - Dengue, Japanese Encephalitis, Yellow Fever, Zika

Question 1

name all the Flaviviruses

Answer 1

Zika, Hep. C, Japanese Encephalitis, Dengue, Yellow fever

Question 2

what are the chances of developing clinical disease for Dengue, JE and Zika

Answer 2

Zika: 1 in 5 chance of developing clinical disease

Dengue: 1 in 10 chance of developing clinical disease

JE: 1 in 25 to 1000 chance of developing clinical disease

Question 3

how are the Flavi’s spread

Answer 3

mosquitos

Question 4

what serotypes of dengue circulate in endemic areas

Answer 4

all serotypes of dengue - serotype 1, 2, 3, 4 circulate at the same time

Question 5

how is dengue spread?

Answer 5

mosquitos

Question 6

what are clinical symptoms of dengue?

Answer 6

macropapular rash 
fever 
very severe pain in joints and muscles 
some people develop warning signs
includes increased vascular permeability

Question 7

what are the warning signs of dengue and what do they cause and why

Answer 7

warning signs develop when the disease becomes more serious
includes:
- clinical accumulation in the tissues and spaces of the body as they have developed capillary leak syndrome. leakage of plasma
- severe thrombocytopenia bad!!!
- can have a petechial rash where blood leaks from capiliaries - can cause BP to drop and organ failure

Question 8

what occurs when water is given to someone with dengue why?

Answer 8

• as they have increased vascular permeability water will cause more fluid to leak into the tissues and can make situation worse
  treatment is to not give fluids for dengue

Question 9

how common is dengue infection - where is it most common in australia

Answer 9

• we dont have dengue in aus
  but we do have it in return travellers
  dengue is as common than flu infection in travellers
  its more common than Hep. A

Question 10

how many vaccines are there for Dengue
what is it
what does it cover
how effective is it

Answer 10

only 1 vaccine - only vaccine on the market
Chimerivax
it is a chimeric, quadrivalent vaccine
covers all 4 antigens for the 4 serotypes
not very good efficacy - 60%

Question 11

what is the effect of the dengue vaccine in seropositive and seronegative patients

Answer 11

• in seropositive patients that have previously had dengue the vaccine prevents them from infection and prevents them from getting severe disease
• in those that are seronegative patients the vaccine lost protection from infection and there was an increased risk of developing severe disease

Question 12

what is the recommendations for the dengue vaccine

Answer 12

• as the vaccine works best for those that are seropositive they only recommend to use the vaccine in places where the virus is endemic
• as these people have most likely been infected, and be seropositive
• therefore the benefits outweigh the cons in these areas

Question 13

what is the transmission cycle of JE

Answer 13

• it is a virus that is transmitted through animals
• pigs and birds act as amplifiers of the virus
• mosquitos transmit the virus and humans are accidentally infected by mosquitos - we are not apart of the cycle
  humans become infected when they are in animal/mosquito environments

Question 14

what are the symptoms of JE and how long do they take to appear

Answer 14

ranges from febrille illness - headache fever and rigor to aseptic meningitis to encephalitis

incubation is 5-15 days

Question 15

what age group is at risk of developing neurological illness from JE?
who normally gets JE?

Answer 15

there is age specific outcomes for JE infection - the older you are the more likely you are to develop neurological illness (5-10x more likely)
those at high risk are over 50 years old
younger people are not as at risk of developing neurological disease
although most JE infections occur in young children

Question 16

how is JE diagnosed?

Answer 16

collect blood and do RT-PCR to diagnose infection when patient is viraemic - would allow diagnosis within days
serology can be taken later once they seroconvert to confirm the diagnosis
MRI can also be used in early infection to see brain changes and diagnose severe JE - water accumulation in the brain indicates inflammation

Question 17

what is the prognosis of JE?
who dies
who survives?

Answer 17

20-30% of people will die from JE

70-80% will survive from JE infection:
out of the surviving 50% will have a severe disability including paralysis, movement disorder etc
the other 50% will have a mild disability - learning disorder, seizures etc.

Question 18

what is the risk for JE for travellers?

Answer 18

1 in 250,000 travellers will get a clinical JE infection in endemic areas
dont have to travel for over a month to be at risk - most people who get sick were there for less than a month

Question 19

what time of the year does most disease transmission of JE occur

Answer 19

may to october

Question 20

how is JE treated?

Answer 20

it cant be treated

Question 21

how many vaccines for JE are there?

what are they named and what are their features?

Answer 21

2 vaccines available - both good vaccines!

IMOJEV

• live attenuated chimeric vaccine that uses the internal structure of yellow fever virus and uses the JE envelope
• high efficacy
• rapid immune response
• one dose needed
• no safety concerns

JESPECT

• inactivated vaccine
• high conversion rates but Ab titres wane quickly hence need a booster every 2 years
• no safety concerns

Question 22

where is yellow fever found

Answer 22

africa and south america

Question 23

how is yellow fever spread

Answer 23

by mosquitos

Question 24

what transmission cycles does yellow fever have

Answer 24

it has a urban cycle and a city cycle

urban cycle: the virus is transmitted in urban areas

jungle cycle: the virus is amplified in primates and by mosquitos - this is an issue as the virus cant be eradicated unless the primate population is eliminated
hence virus is maintained in the jungle cycle

Question 25

what are the clinical features of yellow fever

Answer 25

first signs: fever, chills, back pain
virus will attack the liver and cause hepatitis
more severe symptoms will include abdominal pain, vomiting, jaundice
leads to multi-organ failure

Question 26

how do you diagnose yellow fever?

why is it difficult?

Answer 26

yellow fever looks alot like other diseases / infections such as malaria, typhoid, etc. and they all circulate in the same areas
PCR is used to diagnose the virus first
then serology will be used once the patient has seroconverted to confirm diagnosis

Question 27

how is yellow fever prevented?

Answer 27

yellow fever vaccine

• live attenuated vaccine
• induces neutralising ab’s
• very effective

Question 28

what should you consider before giving the yellow fever vaccine?

Answer 28

yellow fever vaccine
should not be given to those allergic to eggs
should not be given to immunocompromised, children/infants, or pregnant women
there are adverse events that can occur from giving the vaccine such as post vaccination encephalitis and viscerotropic disease

Question 29

what are the adverse event of yellow fever vaccine and who should you avoid giving the vaccine to

Answer 29

avoid giving vaccine to immunocompromised, infants and pregnant women
adverse events from the vaccine include:
Post vaccination encephalitis
- most cases of this are in children this is why we dont vaccinate the kids

Viscerotropic disease

• yellow fever like illness- its actually just yellow fever disease!!
• risk if youre over 65
• experience organ failure
• treatable if caught early
• other wise risk of death 60%

Question 30

how is zika kept alive?

Answer 30

zika is kept alive in primates and spread by mosquitos

humans are accidentally infected by zika

Question 31

how can zika be transmitted

Answer 31

blood, breast milk, saliva, semen

can cross the placenta from mother to baby - biggest issue

Question 32

what are the symptoms of Zika?

how many people develop symptoms?

Answer 32

Zika causes mild fever / rash that lasts a week
the disease is self limiting

only 20% of people develop symptoms! 80% of cases are asymptomatic

Question 33

what is the issue with Zika

Answer 33

causes foetal abnormalities - microencephaly

Question 34

how is zika diagnosed?

Answer 34

PCR of blood to diagnose Zika infection

can confirm diagnosis with serology once patient has seroconverted

Question 35

how do you manage pregnant women diagnosed with Zika

Answer 35

• confirm diagnosis using PCR and serology

- can scan baby every so on to see if changes has occured

Question 36

can zika be sexually transmitted?

Answer 36

yes. zika is present in the semen for up to 90 days post infection