Dengue Fever — Nancy Rihana, MD

hello everyone so our topic for tonight is going to be about dengue fever dengue fever is the most common arbovirus infection of humans it’s a transmitted by a mosquito it’s usually if it’s a single it’s a floppy very de single-stranded RNA we have four serotypes than one two and three and four once you get infected with a certain stereotype usually you acquire a long-life serotypes specific immunity it’s usually a self-limited acute if a bright viral illness that has plugged the tropical region of the world for centuries as we can see it’s a part of the genus Flavia of the family fluffy verita along with the West Nile virus yellow fevers st. Louis and Japanese encephalitis and all the others let’s go back a little bit in history as we can see dr. Benjamin Rush a professor of chemistry and medical theory at UPenn was a was the first one in back in 917 80 to describe the dramatic symptom of dengue as a breakbone fever and then world war two back in 1930 played an important role in the spread of dengue fever through Asia Pacific region until the 1970 the epidemics were only limited to nine tropical countries but in the last 50 years and secondary to the unplanned urbanization in tropical developing countries secondary to the modern transportation lack of effective mosquito control and globalization we had an alarming rise in cases with incidence increasing 30-fold and now dengue has became endemic in more than hundred countries in the tropical and subtropical region of the world it’s estimated now that it’s we have fifty two hundred million infections per year worldwide over 2.5 billion people are at risk of infection the mortality can go between five percent and less than one percent with appropriate therapy usually we get seasonal outbreaks since the warm and the wet conditions favor the development of these mosquitoes that usually breathe in water and whenever we have high humidity and rain falls we get stagnant pools where this mosquito population can explode some countries they have a risk of dengue that exists year-round these countries where we have the hyper endemic dengue but usually finally the worldwide outbreaks occurs every twenty to forty years as you can see here this map shows the regions that are potentially susceptible to dengue based on climatic and environmental variables such as temperature and available moisture and now because of the global warming we’re expecting that the dengue risk is going to move further nose let’s talk a little about the vectors the main vector as we all know as I added a gypsy it’s a yellow fever mosquito it’s usually a day biter and lives in the tropical and subtropical areas as for the second factor the AIDA Sal Bob takus it’s also called the Asian tiger mosquito it’s a day and night biter it’s as competent as I had as a gypsy to cause a transmission of the dengue virus but it doesn’t do it as often because it doesn’t bite a human as often and the iotus albopictus has the capability to sustain colder weather so we see it more in the northern areas so what do you think this one is as you can see the white markings on the legs and the bright silvery lyre shape dorsal pattern this is the mosquito that came from Africa and this is is a gypsy as for this one we have the black and white stripped legs and the small black and white stripped body was a single long silvery dorsal stripe and this one originated from Asia and this is the tiger mosquito yes dengue is moving north us outbreaks to date and they are mostly caused by dengue one in 2001 we had an outbreak in Hawaii 2007 in Texas and before 1934 the first outbreak in Florida was in Key West in 2009 we had 22 cases 2010 66 cases of locally acquired dengue 2012 for resident locally acquired dengue 2 were in Miami and 2 near Orlando with another 112 cases were imported from elsewhere let’s talk about Peto Genesis so usually after the bite of dengue the virus infects immature dendritic cells that they go

and migrate to the lymph nodes where you get an activation of the cellular and humoral immune response the viral will continue to replicate in the macrophages for three to six days which is the incubation period prior to viremia and once the virus six eight hours later you start having the symptoms of dengue fever and then the verinha and the fever will both ends together but once the fever starts there’s a period of two to ten days where the victim can cause an infection in the nest mosquito that bites him or her and once the mosquito is infected with dengue virus it remain infectious for its entire life which is one months now we all know that the secondary infection of dengue is the one that leads to the more severe cases but what is the mechanism behind that it’s a it shows that it’s because of the antibody dependent enhancement because once you’re infected with a certain stereotype of dengue you develop neutralizing antibodies against the certain stereotype but you develop a transient cross protection against the other serotypes so once you’re infected with the second Sara type you will get immune complexes between the dengue virus and the non neutralizing antibodies and these immune complexes will infect the macrophages and will cause an exaggerated immune response with a cytokine storm which will disrupt the vascular permeability in here on this this slide we’re trying to explain how the pathophysiology of endothelial dysfunction in the cases of severe dengue secondary infections occur even though the mechanism is still unclear but there’s a hypothesis that says that the virus was it’s non structural proteins bind to the glycocalyx layer of the endothelial cell wall causing the release of heparin sulfate into the circulation which is an anticoagulant and transiently disrupting the endothelial cell wall causing leakage of protein coagulation factors to the extra endothelial space and this is how you get the plasma leakage and all this clinical manifestations so now we have a revised hook the W word house organization has did a revised classification in 2009 replacing the one that was in 1997 as you can see they divided into dengue without warning signs then give us warning signs and severe dengue dengue without warning size at the is characterized by fever and two of the following nausea vomiting rash acts and pains leukopenia and positive torniquet sign as for the dengue was warning time and was warning signs this is the one the very important one because this should alarm us about a risk of developing into a severe dengue is the dengue as defined before with any of the following abdominal pain or tenderness persistent vomiting clinical fluid accumulation mucosal bleeding lethargy restlessness liver enlargement or laboratory increase with the rise and hematocrit and a rapid decrease in platelet count and the dengue was warning sounds is the one that usually can progress to severe dengue severe dengue is a fatal case of dengue fever this is the dengue was at least one of the following criteria either you have a severe plasma leakage leading either to dengue shock syndrome or to fluid accumulation with respiratory distress or you have severe bleeding dengue hemorrhagic fever or severe organ involvement it can involve the liver causing transaminases of 1,000 or more CNS with impaired consciousness or congestive heart failure or failure of other organs so after an incubation of three to seven days we have three phases of disease the fabric phase the critical phase and the recovery phase the febrile phase which usually lasts three to seven days it’s characterized by the fevers the headaches the malla and art algea for that it’s called the breakpoint fevers and you can have a transient macular rash and if there’s any symmetric manifestation in the space that they will be very mild like petechiae bruising mild or moderate rumba site opinion and very mild transaminases then comes the critical phase and this phase usually occur at day four or seven of the illness it’s around the time where you start having the fever starts to wane and in this phase you will notice progression of leukopenia and thrombocytopenia and this is the critical base because this phase is the phase where you can have the plasma leakage can occur leading to the dengue shock syndrome – the third spacing – the mo dynamic and stability or the

hemorrhagic manifestations also can occur in the critical phase with the skin and mucosal bleeding whose only minor plasma leakage sorry and shock recovery phase recovery phase is the phase where you get resorption of all these leak the plasma you get stable hemodynamic status again the urine output will increase in this phase usually people can develop a rash that could be very mild maculopapular rash or a severe leukocyte or classic vasculitis that resolved with discrimination over with one or two week period and it’s usually followed by profound fatigue that lasts for several weeks so here we can see the hemorrhagic some of the hemorrhagic manifestations of dengue fever in the first panel we can see the typical petechial rash in an infant with a dengue on this panel B you see minor bleeding around the injection site which is a very common feature in dengue in panel C you see a hematoma and a patient with a severe and in panel D you see in the recovery phase this is the maculopapular rash the macular rash surrounded by this white islands it’s very characteristic for that so here I’m gonna pinpoint again about the importance of these warning signs whenever you have things you have to very be very careful about the warning signs because they are the ones that alarms you that this patient will need to strict observation medical intervention needs very frequent monitoring of his hematocrit and blood pressure the warning signs again are the abdominal pain or tenderness persistent vomiting clinical fluid accumulation mucosal bleed lethargy restlessness liver enlargement and an increase in hematocrit concurrent with a rapid decrease in platelet count diagnosis it’s usually it’s based on the clinical signs with or without travel history nowadays and the diagnostic test we have two types of diagnostic tests we have the direct that are able to detect the vital components in the serum which are the reverse transcriptase PCR and the non-structural one antigen detection by Eliza or lateral flow rapid tests and the indirect tests which are the serology as you can see from the first day of illness we can start detecting the dangus through the direct diagnostic tests which are either detecting the nucleic acid by the reversion of scepters PCR or the non structural proteins that is an express produced by the virus as for the first day as early as the fourth day you can start seeing the IgM and the blood non-structural one antigen it’s a structural protein secreted by all the flavia vallega it’s detectable up to ten days after the onset of the illness and disappear once the seroconversion has occurred there’s a lot of methods that can diagnose that can detect the non-structural antigen you have the eliza the rapid task lateral flow the serology also for this non structural protein and you there’s a lot of commercial rapid tests available that takes only 15 minutes to detect this antigen but they are not fda-approved and the problem with this test that is also cross-react because it’s positive and all other flow riverita the rapid tests are available for the serologies along with the non structural protein and they take only 15 minutes with a problem they’re not available in the US for the reverse Ratatosk pcr they are useful for the first five days of symptoms with a very good sensitivity and specificity they are FDA they were FDA approved back in 2012 for diagnostic use in the US and they start distributing them back in July 2004 as for the IgM serology it’s detected as early as four days after the onset of fever false positive can occur secondary to cross reactivity with other flatty varada sensitivity is also it’s good if it’s a primary infection but it goes down if it’s an secondary infection and the FDA has approved the use of a Mac Eliza back in April 2011 usually if you get a single sample serum sample it just gives you a presumptive diagnosis the only way to get a confirmatory diagnosis is to get paired sample that shows an IgM seroconversion hi Gigi Eliza it’s not fda-approved it’s commercially available it’s also a confirmatory test the good thing about it that it helps you differentiate between primary and secondary infections it helps you it tells you if the secondary infection infection if you have more than four times rise in a

paired sample now these two last tests which are the vital cell culture and the prnt are very labor intensive and they require research laboratories or certain State House laboratories and they take a long time but they are able to stereotype to the dengue virus and they are very specific for more information about these tests you can go to the side management of course there’s still no medication no drugs available for the dengue virus so the management remains supportive don’t give aspirin steroids and say it’s because of increased risk of bleeding so we only have acetaminophen for the pain and fever all you need to do is monitor for development of plasma leak by checking serial hematocrit hydration status blood transfusion only if significant bleeding because we don’t want to cause any a autogenic pulmonary edema because as well as we saw that in the recovery phase we’re going to have a resorption of all the plasma that was leaked out so in case we over we gave him a lot of fluids we’re going to lead to a orogenic pulmonary edema this algorithm is also from the World Health Organization and it tells you step by step in the case of hypotensive shock it tells you step by step in the case of hypertensive shock how to challenge the patient with fluid followed by checking the hematocrit and assessing the patient status and then deciding if it needs to be recharged or not yes no vaccinations yet but as it shows that the ideal then vaccine should be able at least to protect against disease buckos by all four serotypes but however if we think about it because the incidence of severe disease following a third or fourth dengue virus infection is very low it’s possible that a trivalent response may be sufficiently protective while no licensed dengue vaccine is available several vaccine candidates are currently being evaluated in clinical studies the candidate currently at the most advanced clinical development stage is the den box it says now in Phase three efficacy studies it’s a tetravalent live attenuated dengue virus stain based on a shimmery yellow fever and a dengue virus the result from the phase 2b trial was that was done in Thailand has been published in September 2012 and showed that was was he this vaccine was able to induce a trivalent neutralizing antibody response in 90% of the children but for unclear reasons the vaccine failed to protect against the benefit – which was a prevalent serotypes in the region of Thailand a candidate another candidate of dengue vaccine that was developed by the National Institute of Health is a TV 0:03 and the phase 1 clinical trial was recently published in the Journal of infectious disease issue of January 17 2013 this is this the phase 1 clinical trial was able to show that a single dose of this live at unity the tetravalent vaccine was able to induce a trivalent or greater neutralizing antibody response in 90% of the flaafy virus naive adults and what is attractive about this vaccine that the production cost of it it’s very very inexpensive it’s less than $1 which made it very attractive to the developing countries and now a phase 2 trial is going to start to evaluate the TV 0:03 and its capacity to create an immune response will begin soon in Brazil and Thailand and of course now in the horizon because we are now we have a dengue mouse model that’s been validated and demonstrated to be a suitable test system for the antiviral drugs there’s a lot of studies and clinical trials that are going on still an early phase two that are trying to study the new antiviral medication and medications that are targeting them your response to dengue there is like some exotic new approaches to target the vector are going on one of them is a gene modified male mosquito that contains a gene that causes the offspring to die before maturing the trial was already done in Cayman Islands in Brazil and in Malaysia and they are using it where they released 3.3 million of gene modified mosquitoes is a gypsy resulted in 80% reduction in the mosquito population in the Cayman Islands 90% in Brazil but the mosquito control officials in the Florida Keys are awaiting approval from

the federal government to begin releasing hundreds thousands of these gene modified mosquitoes first in the US they will be the first in USA but now remains the fear of the unknown what if these gene modified mosquitoes turned out to be superbugs immortal spreading other diseases so question mark about that alternative strategy is embryonic introduction of strains of the obligate intracellular bacterium or Basia into the IFS a gypsy and the vulva she infected is a gypsy are partially resistant to the dengue virus infection and since this will be she will able to invade the natural a gypsy population this will lead to possibility of induction of widespread biological resistance to the dengue virus and is a gypsy population so until then the best hope of stopping this epidemic and the advance of dengue fever relies on our individual actions which is the mosquito control is a most effective approach by using insecticide to reduce the breeding sites discard any tires other containers that accumulate water after every rain wear repellents and maybe convincing people to stay inside this is a top 10 mosquito love nests that’s published by the Ontario Ministry of Health thank you you