Welcome to Mayo medical laboratories hot topics these presentations provide a short discussion of current topics that may be helpful to you in your practice our topic for today is the introduction of two new dengue virus serologic tests that offer improved detection of dengue virus infection.
Our speaker for this program is doctor early feel director of the infectious disease serology laboratory at Mayo Clinic in Rochester Minnesota doctors deal thank you for presenting today.
Thank you for the introduction and also to the viewers for joining us today this hot topic will focus on the available diagnostic testing options for detection of dangerous virus with a brief review of the clinical manifestations of disease treatment and prevention for more detailed discussion of these latter topics please refer to doctor Jane hot is hot topic entitled Dinky fever and update released on May thirtieth twenty fourteen.
Before we begin I should mention that I have no financial or another complex to disclose.
During this presentation, I’ll provide some background on Dinky virus and briefly review the clinical manifestations of infection all next focus on the available diagnostic methodologies including testing by now click acid implication tester gnats and evaluation of the urologic response to infection by detection of both an engine from in antibodies to dainty buyers finally I’ll conclude with a brief discussion of treatment and prevention of thank you virus infection.
To begin to thank you very says a member of the flavivirus family of viruses which also include west Nile virus St Louis encephalitis virus and yellow fever virus among others these are all enveloped positive-sense single-stranded RNA viruses.
The danger virus complex is comprised of four different thank you bear serotypes which are roughly sixty-five percent genetically identical to each other and all members are transmitted by eighty species mosquitoes specifically eighties. N. eighties upper picked as shown on the right importantly humans are the primary reservoir for doing your virus which limits the transmission cycle of this virus from mosquitoes to humans and back to ask you does following infection the incubation period in humans can range from three to twelve days prior to development of symptoms.
Thank you virus is most prevalent in the so-called Dinky belt which is roughly outlined by the red lines in the image shown here link between thirty degrees north and south latitude these regions are typically in tropical and subtropical areas where winter temperatures do not fall below fifty degrees Fahrenheit within this belts roughly two point five billion people are at risk of contracting the virus among whom approximately fifty to one hundred million are infected annually and five hundred thousand patients develop severe disease over the last fifty years according to the World Health Organization there has been a thirty-fold increase in the number of danger infections elevating the dissemination of this virus to a pandemic threat with regards to debut virus infections in the United States the vast majority of cases are acquired during travel to endemic regions however eighty species mosquitoes are endemic in the United States and prior outbreaks have been recorded in southern states including Texas and Florida so the potential for additional outbreaks and further dissemination of Dan gate into the continental US is not insignificant.
With regards to clinical presentation following exposure to the virus, approximately fifty percent of individuals will remain entirely asymptomatic the remaining fifty percent of patients can present with one of three disease manifestations the first of these is undifferentiated fever which presents with nonspecific symptoms very similar to other causes of acute febrile illnesses for many of these patients unless specific day get virus testing is performed the diagnostic because will remain unknown.
These patients are typically younger children or those experiencing their first day give virus infection and will recover on their own without the need for medical attention.
The second manifestation of disease has Dinky fever which can be with or without hemorrhage these patients are typically older children or adults and present with prolonged high fever and severe headache Roger orbital pain in my Alger well some mild epithelial hemorrhage may occur with dengue fever these patients do not progress to significant plasma leakage which is a hallmark of dengue hemorrhagic fever or Dinky shock syndrome which is the third potential clinical manifestation following infection with thank you, virus individuals, with dengue hemorrhagic fever progress through three different phases including the febrile phase which is indistinguishable from dengue fever followed by the critical plasma leaker hemorrhage phase which occurs around the time of fevered effervescence some of the warning signs for progression to plasmin leakage include increased capillary permeability elevated hematocrit pleural effusion and hypovolemia if these signs are noted in vascular permeability is not countered patients can progress to shock organ failure and ultimately death finally for patients who survived the plasma leakage stage the third phase of dengue hemorrhagic fever is a convalescent-phase at which time fluids that have leaked from the intravascular space are reabsorbed.
Diagnosis of danger virus infections is multifactorial and dependent on the presence of appropriate clinical symptoms and a proper exposure history there are also a number of laboratory methodologies available to confirm the diagnosis these methods include culture though this is available only through the CDC and as such has limited clinical utility in the acute care setting more commonly used testing methods include nucleic acid implication tests are not what you’re limited to select reference laboratories in serology for detection of both antigen from in antibodies to the virus.
Importantly the decision of which tests to choose among these is largely dependent on the duration of patient illness and understanding of the immune response to infection which I will briefly review here.
At the time of mosquito transmission viremia rapidly spikes and is detectable by molecular methods for the first four to six days following symptom onset and during acute disease during the very make period and up to ten days following symptom onset the tank you virus and this one antigen is released and also detectable.
The AGM antibody response today give virus infection becomes detectable roughly four to five days following symptom onset and remains elevated for two to three months finally I G. G. antibody levels become detectable five to seven days following symptom onset and will remain elevated for years to decades.
So keeping these anally profiles in mind our first focus on not testing to detect any virus Arnie this methodology is most useful during the acute disease typically within the first five days of symptom onset during which time viral titers are still elevated notably there are no FDA cleared molecular **** retain your virus however the CDC in a small number of larger reference laboratories have implemented their own laboratory-developed tests, in general, the sensitivity of molecular essays range from eighty to ninety percent which is largely dependent on when the sample was collected with respect to symptom onset these essays have a high specificity however of ninety-five percent or greater and have the ability to differentiate between the various stinking virus zero types.
Importantly a negative not result for dengue virus should not be used to rule out infection and providers are strongly encouraged to follow up with your logic testing if the risk of infection is high.