1. West Nile virus is transmitted through mosquito bites and can cause fever, headache, body aches, and in severe cases encephalitis or meningitis. 2. It is diagnosed through physical exams, health history, and laboratory tests including antibody tests, nucleic acid amplification tests, and lumbar puncture. 3. Antibody tests like ELISA can detect IgM and IgG antibodies to determine if a person has been recently or previously infected with West Nile virus.

1. West Nile test:Virus
Introduction
It iscaused by infectedmosquitoes.PeoplewhogetWNV usuallyhave nosymptomsbuttheymay
include fever,headache,bodyaches,skinrashandswollenlymphgland.Entryof virusintothe brainis
howeverlifethreateningandcause inflammationof the brain(encephalitis) orinflammationof the
tissue thatsurroundsthe brainand spinal cord(meningitis).
Usuallyolderpeople &those withweakimmune systemare more at risk.
There are nospecifictreatmentandvaccine available forhumanWNV disease.
Test for west Nile virus
It can be diagnosedbyaphysical exam,healthhistoryanda laboratorytest.
Mainlythree maintetsare performedtodiagnose the virusandtheyare
1. Antibodytes
2. Nucleicacid amplificationtest
3. Lumbar test
1. Antibodytest:
It can be diagnosed byELISA whichmeans Enzyme-linkedimmunosorbentassay. Itis furtherdivided
intofollowingtypes
 Indirect”ELISA
 SandwichELISA
 Competitive ELISA
a. Indirect”ELSIA
In thismethodtake antigentobe testedandadd itin the microtiterplate aftersome time due tocharge
interactions itisadhere tothe plastic.
 Bovine serumalbuminorcasein(non-reactingprotein) solution is added to well (usually 96-
well plates)
Primary antibodyisadded intoitwhichthenbindstothe antigencoatingthe well.
Thenthe secondaryantibodyisadded thatbindsto the primaryantibody. The secondaryantibody has
an enzyme thatattachedto itwhich has verysmall effectonthe bindingpropertyof the antibodies.
Sometimesthe primaryantibodyitself binds tothe enzyme. Forthispurpose substrate isaddedforthis
enzyme. Due toreactionwithenzyme itscolorchangeswhich shows thatthe secondaryantibody
attaches to primaryantibodythatstronglyshows the donorhas an immune reactiontothe testantigen.

2. The higherthe concentrationof the primaryantibodypresent the more will be colorchanges.
For quantitative studyspectrophotometerisused.
SandwichELISA:-
 A knownquantityof antibodyis boundonthe surface andnonspecificbindingsitesare
blockedonthat surface thenantigenhavingsample isintroducedintothe plate.Unbound
antigenisthenwashedfromthisplate.
 In thissample aspecificantibodyisaddedtowhichantigenisattachedhence forminga
sandwichi-e one antigenisstuckbetweentwoantibodies. The plate iswashedtoremove the
unboundantibody
 Thensubstrate is addedthat resultsinthe colordevelopmentwhichisdirectlyproportional to
the antibodyconcentration
Competitive ELISA
 In this method the unlabeled antibody is incubated in the presence of its
antigen (sample).
 These antigen/antibody complexes are then added to an antigen-coated
well.
 Unbound antibody is removed fromthe plate by washing. Morethe antigen
in it more will be antigen/antibody complexes and hence less are the
unbound antibodies for antigen in the well (so named as "competition".)
 The secondary antibody, specific to the primary antibody, is added. This
second antibody is coupled to the enzyme.
 A substrateis added into it that will generate a color.
Reference Values
IgG: negative
IgM: negative
Reference values apply to all ages.

3. Interpretation
IgM Antibody:
ISR RESULT INTERPRETATION
< 4.47 Negative No detectable IgM an
tibody, individual
does not appear to be
infected with WN
virus
>5.66 positive A positive IgM result
may not indicate a
recent infection.
A positive result is consistent with the acute phase of West Nile virus (WNV)
meningitis or encephalitis. In the very early stages of acute WNV infection, IgM
may be detectable in cerebrospinal fluid before it becomes detectable in serum.
A negative result shows that disease is absent. However, specimens drawn too
early in the acute phase may be negative for IgM-specific antibodies to WNV. If
WNV central nervous system (CNS) infection is suspected, a second specimen
should be collected in 1 to 2 weeks and tested.
IgG Antibody:
A positive result is consistent with CNS infection with WNV sometime in the past.
Nucleic Acid Amplification Test
As the name indicates this test is used to amplify and measures the
West Nile virus's genetic material for the detection of the virus.

4. It can detect a current infection with the virus even when antibodies to
the virus are not detectable.
In order to detect it, it must be present in the sample because this test
is specifically used to detect WNV.
Their primary hosts are birds, so virus levels in humans are usually low
as compared to birds and do not persist for very long.
This test is most useful for detection of WNV in donated units of blood,
in the blood of living tissues and organ donors, or organs, and for
testing mosquito pools and birds to detect the presence and spread of
WNV in the community.
This test is also beneficial because it can detect the blood or tissues of
a died person who has died as a victim of this virus
Lumbar puncture(spinal tap).
The most common way to diagnose meningitis is to analyze the
cerebrospinal fluid surrounding your brain and spinal cord. A needle
inserted between the lower vertebrae of your spine is used to extract a
sample of fluid for laboratory analysis. The fluid sample may show an
elevated white cell count — a signal that your immune system is
fighting an infection — and antibodies to the West Nile virus.