This course introduces learners to a variety of infectious diseases using a patient-centered, story-based approach. Through illustrated, short videos, learners will follow the course of each patient’s illness, from initial presentation to resolution. Integrating the relevant microbiology, pathophysiology and immunology, this course aims to engage and entice the learner towards future studies in microbiology, immunology and infectious diseases. The patient-centered videos included in this course were created as part of the Re-imagining Medical Education initiative, led by Charles Prober MD, Senior Associate Dean of Medical Education at the Stanford School of Medicine. This initiative was the first of its kind to explore the collaborative creation of foundational medical education online content by inter-institutional teams of faculty. The content presented in this course was created by faculty from Stanford University School of Medicine, in collaboration with The University of Washington School of Medicine, Duke University School of Medicine, UCSF School of Medicine, and The University of Michigan Medical School. Support for this initiative was provided by the Robert Wood Johnson Foundation and the Burke Family Foundation. PLEASE NOTE: Information provided in this course is for educational purposes only and is not intended to be used for diagnostic and/or treatment purposes.
Viral Meningitis
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From the course by Stanford University
Stories of Infection
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From the lesson
Viral Infections Part 2
In Module Five, we will explore five additional infectious diseases caused by viruses. We will also apply our knowledge of the immune system to explore the use of vaccines, and understand the history of the MMR vaccine. By the end of this module, learners will be able to interpret the clinical presentation of these five infectious diseases and describe the relevant microbiology, pathophysiology, and immunology.
Meet the Instructors
Maya Adam, MDLecturer
Stanford School of Medicine
Today, we're going to be talking about enteroviruses, a group of viruses that
are responsible for a wide range of diseases including polio, hand foot and
mouth disease, and even the common cold.
Enteroviruses can also cause infections of the central nervous system
as they did in this 28 year old teacher named Todd.
Todd had been teaching at the university preschool where he was
also doing research for his master's degree in education.
One early evening in August, Todd was brought to the By the mother of one of
the children in his class who also happened to be a physician.
She had come to the school to pick up her son when one of the other teachers told
her that Todd was lying down in the library feeling terrible.
She went to speak with Todd and took note of a concerning collection of symptoms.
She also saw that he looked distinctly unwell, so
she decided to bring him to the.
At the Todd tells the physician on duty that he's been well until
the day before when he noticed that he had a bit of a sore throat.
He explains that a lot of the kids at the preschool are sick with summer colds, and
he thought he had just caught a cold from one of them.
But today, just after lunch, he began to feel feverish,
developed a terrible headache, and began vomiting.
The Physician asks Todd if he's traveled anywhere recently,
or if he's noticed any unusual mosquito or tick bites.
But Todd says he's been teaching through the summer and
hasn't had any unusual bites or exposures.
He's also not currently taking any medications.
During his physical exam,
the attending physician notices that Todd has a low great fever and a stiff neck.
He also experiences a lot of pain extending his leg
from a position where his thigh is bent at the hip and knee at 90 degrees.
The attending notes that Kernig's sign is positive and also notes that when Todd
is asked to lift his head off the table he involuntary lifts his legs as well.
Todd's neurological exam is normal.
He's lucid and knows where he is and the correct date and time.
This collection of signs and symptoms, nuchal rigidity, headache,
fever and emesis, leads the attending to have a high index of suspicion that
Todd is suffering from meningitis.
Meningitis is an acute inflammation of the membranes that cover the brain and
spinal cord.
These membranes are collectively known as the meninges, and
they can become inflamed by infection with viruses,
bacteria and other microorganisms, and less commonly by some drugs.
The Physician performs a lumbar puncture to obtain a sample
of cerebrospinal fluid that can then be used for analysis.
The LP sample is sent on for a cell count, gram stain, and analyses of glucose and
protein levels, and one tube of CSF is saved for future molecular diagnostics.
The CSF gram stain is negative for bacteria.
Glucose levels are normal and
there's a modest increase in CSF protein concentration.
Lymphocytes in the CSF are elevated.
This is consistent with a diagnosis of aseptic meningitis, but
the exact cause of the inflammation is still unknown.
Elevated CSF lymphocytes can be caused by a variety of conditions
including viral meningitis, tuberculous meningitis,
a subarachnoid hemorrhage and some autoimmune conditions.
Because of Todd's exposure to sick children,
his symptoms of an upper respiratory tract infection, and the time of year,
the Physician feels that viral meningitis is highest on the differential.
He sends the tube of CSF saved earlier for molecular diagnostics,
including PCR for enterovirus and herpes simplex virus,
which are common causes of viral meningitis.
Unlike bacterial cultures, a specific virus needs to be suspected when
a physician is selecting the right test to confirm the diagnosis.
The results of Todd's diagnostics show that his symptoms are caused by
an enterovirus and he's diagnosed with enteroviral meningitis.
Enteroviruses are sometimes transmitted when people inhale or
ingest material that contains infectious viral particles.
Sources of infection include being around others who are ill or
swimming in contaminated water, like the water found in fresh water lakes,
ponds or swimming pools that haven't been adequately chlorinated.
This could explain the seasonal increase in
enteroviral infections during the summer.
Todd likely inhaled or inoculated his oral pharynx with infectious respiratory
droplets containing enterovirus particles while he was teaching at the preschool.
The virus was then able to enter Todd's body, and
colonize the respiratory epithelium,
despite the efforts of the respiratory cilia to protect him from viral invasion.
Todd's body detected the infection, and deployed inflammatory cells and
chemical mediators that lead to his sore throat and fever.
Despite these efforts, the virus was able to persist and replicate,
giving rise to the primary viremia which in turn allowed the virus to
spread via the bloodstream to lymphoid tissues throughout the body.
Replication at these new lymphoid sites produced the secondary viremia
which is when Todd began to show symptoms of enteroviral meningitis.
The viral particles went on to invade the CNS by being carried across the blood
brain barrier in infected leukocytes or by infecting cranial or peripheral nerves.
Because this virus has evolved to be able to
invade the tissues of the nervous system, it's considered neurotropic.
The treatment of patients with suspected viral meningitis
depends on which virus is causing the infection and how ill the patient appears.
Sometimes, specific antivirals are started
while the molecular tests are still pending.
Some patients, particularly those who are at the extremes of age,
either very young or elderly, or those who are immunocompromised,
these patients may be considered for empiric antibacterial therapy for 48 hours
even if viral meningitis, not bacterial meningitis is the suspected diagnosis.
There are a few reasons why.
Firstly, these patients are at higher risk for developing bacterial meningitis.
Secondly they may not mount a vigorous or typical immune response.
And finally, they may not show early signs of deterioration before becoming very ill.
Another option is for
the physician to simply closely observe the patient without antibiotic therapy.
But, if there's any diagnostic uncertainty,
then the benefits of empiric antibiotics greatly outweigh the risks.
Todd's initial testing was very typical of viral meningitis and
the PCR confirmed the diagnosis of enteroviral meningitis.
So his doctor prescribed supportive treatment and
he received pain control medication, anti-emetics and IV fluids.
He was discharged from the hospital the following day and
spent a week recovering at home before he was able to return to work.
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