(calm music)
- Lyme disease is diagnosed
by a combination of features.
The most important
starting point, of course,
is what the patient's experiencing,
the symptoms of Lyme disease.
Unfortunately, the
symptoms such as fatigue
and fever and achiness are common symptoms
in many illnesses.
So, by themselves, the
symptoms cannot be used
to diagnose Lyme disease.
A little more reliable than symptoms
are what are called signs of the disease.
These are more reliable
because they're more unique
to Lyme disease.
For instance, the rash,
that round, red lesion
is fairly unique.
And it's fairly specific for Lyme disease.
So, sometimes we can
make a diagnosis based
on the rash if it's present.
But the rash isn't always present.
If we see the rash and discover it,
then that can actually
be diagnostic by itself.
In the later stages of Lyme disease
there are also signs that you can see.
Facial palsy in the second stage,
swollen knees in the third stage.
Those signs are somewhat
specific for Lyme disease
but not absolutely.
There are other causes of Bell's palsy.
There's other causes of swollen knees.
So, in those later stages
that second and third stage,
the diagnosis needs to be
confirmed by a blood test
which is called a serology blood test.
This blood test measures the antibodies
that are formed by your own immune system
in response to the Lyme
disease bacterial infection.
So, these antibodies are measured using
what's called an ELISA test.
If the ELISA test is
positive, it's confirmed
by what's called a western blot test.
So, this ELISA/western blot combination
is called the two-tier testing strategy.
It is helpful for second and
third stages of Lyme disease
but not helpful for
first stage Lyme disease.
The reason for that is
because it's an antibody test.
Antibodies take weeks to develop.
So, at the initial
presentation of Lyme disease
in the first stage, those antibody tests
may be falsely negative
because the immune system
hasn't had enough time to
produce the antibodies.
Because of that, if the
physician is still suspicious
of Lyme disease and they
can't make the diagnosis
by the rash, then the antibody
test in that first stage
can be done but it should be repeated
three to four weeks later to make sure
that we haven't missed a diagnosis
with a false negative test
in the first few weeks.
What we would like to see in the future
are tests that directly
measure the infection.
These would be tests like
a culture or a PCR test
or an antigen detection test.
Those are the kind of
tests that we rely on
in infectious diseases
for other infections
like HIV or hepatitis C or strep.
There, we're actually
looking at a direct test
that measures the
presence of the bacteria.
Those are obviously much more reliable
than a test that's looking
for indirect measurement
of antibodies which don't
represent the actual infection.
The antibodies represent
the immune response
to the infection.
So, very important difference
between direct tests
which are not generally
available for Lyme disease
and a serology test which
measure immunologic recognition
and immunologic memory.
At the Johns Hopkins Lyme
Disease Research Center,
we're actually looking
at new ways to develop
direct diagnostics tests such as PCR tests
that would directly identify
the bacteria Borrelia burgdorferi
and wouldn't rely on the
older serologic tests.
Since Lyme disease is
a tick-borne infection,
the seasonality of the
disease is linked tightly
to the behavior of ticks.
Nymph stage or adolescent ticks
feed in the late spring and early summer.
They transit most of Lyme disease
because they're very small,
about the size of a poppy seed.
Very difficult for
patients to see or feel.
Because of this Nymph
stage tick feeding pattern,
most of Lyme disease
is actually transmitted
in the late spring and early summer.
Probably 80-plus percent of
the cases are transmitted.
So, we know that there's
a high seasonality
and that May, June, and
July are the big risk months
for acquiring first stage Lyme disease.
Adult stage ticks feed
in the fall and winter
so there is some
transmission of Lyme disease
in the fall and winter
and throughout the year.
But, that's a small percentage of cases.
The vast majority are
transmitted in May, June,
and July and early August.
That's the reason that we
have to be especially vigilant
for unusual symptoms in
the early summer months.
Especially that early
summer flu-like illness
that is not typical, that
lacks typical viral symptoms
like runny nose or prominent cough
or prominent diarrhea.
In the absence of those
typical viral symptoms,
that summer viral-like illness
may actually be Lyme disease.
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