Distinguished future physicians welcome to Stomp on Step 1 the only free videos series
that helps you study more efficiently by focusing on the highest yield material.
I’m Brian McDaniel and I will be your guide on this journey through the Herpes Family
of Viruses.
This is the 4th video in my playlist covering microbiology and we are going to review genital
herpes, cold sores, chickenpox, shingles & Mono.
This is our first video covering viruses.
Unfortunately, with the viruses you have to memorize how many strands the genome is, whether
it is DNA or RNA and if the virus has an envelope.
This is perhaps my least favorite thing to learn for Step 1, but you just have to grit
your teeth and get through it.
Some of the questions on the exam require you to have this info as it will sort of be
a 2 part questions.
For example, based on the question stem you may know the answer is Herpes Simplex, but
when you look at the answer choices herpes simplex isn’t an option.
You will instead see something like “A double stranded DNA virus”.
If you don’t know how to translate your answer into these defining characteristics
of the virus you can’t get that question right.
So we will be referencing this table as we go through the high yield viruses.
This obviously isn’t exhaustive, but it has the most important examples.
And here is the table listing whether or not the viruses have a lipid outer layer called
an envelope.
You can see herpes listed here as having an envelope.
In the general population the term “Herpes” is used almost exclusively to describe genital
herpes simplex.
There are actually 8 members of the family Herpesviridae (AKA Herpesviruses) and most
of them are high yield for the exam.
However, we will not discuss all 8 of these viruses in this video.
Human Herpesvirus 6 (HHV-6) and Human Herpesvirus 7 (HHV-7) are very low yield for the exam
so we will skip them.
We also will hold off on discussing Human Herpesvirus 8 (HHV-8 or Kaposi Sarcoma) until
a later video that will discuss HIV & AIDs in depth.
This family includes some of the most common and contagious infections in the general population.
Over 90% of people have 1 or more herpes infections.
However, for a huge majority of the time these infections are not active.
After an initial symptomatic period they have prolonged latent phases where the inactive
viruses hide from the immune system.
In some cases there are sporadic periods of reactivation where the patient again becomes
symptomatic.
The symptomatic periods of these infections are usually self-limited, but there is no
cure to eliminate the virus or prevent reoccurrences completely.
Some patients don’t even know they have the infection as even the primary infection
can be asymptomatic or very mild.
The diagnosis of these viruses is usually made clinically.
However, there are tests that can aid in the diagnosis.
A Tzanck Test (AKA Tzanck Smear) is a rapid test that can be performed when a herpes virus
is suspected.
A skin vesicle is broken open and smeared on a slide with a stain.
Microscopically if multinucleated giant cells with intranuclear inclusions is visible it
is a positive results.
Here is a picture of what a positive tzanck test looks like.
There are 2 types of Herpes Simplex, HSV-1 & HSV-2.
HSV-1 presents primarily on the lips or mouth (AKA “Cold Sores” or Orolabial Herpes)
while HSV-2 presents primarily on the genitalia.
HSV-2 is most often an STD while HSV-1 is mostly spread by saliva.
However, there is significant overlap between types and you can get both viruses via either
route and in either area of the body.
In both cases Herpes Simplex can be asymptomatic or cause painful fluid filled blisters on
the skin or mucous membrane that can progress to ulcerations.
Genital herpes typically has multiple lesions while orolabial herpes more commonly has a
single lesion.
Here is a picture of orolabial herpes and I think you get the point so I’ll spare
you all from looking pictures of genital herpes There may also be non-specific symptoms before
the lesions occur called a Viral Prodrome.
The prodrome can include fever, malaise, and tingling in the area that later shows the
lesions.
HSV-1 & HSV-2 are lifelong infections with asymptomatic periods where the virus lays
dormant in sensory neurons.
The virus mostly lays dormant in the trigeminal ganglia after Orolabial Herpes while Genital
Herpes usually results in the virus lying dormant in the sacral ganglia.
There is currently no cure for the virus, but treatment usually involves antiviral drugs
to reduce the severity, duration and risk of transmission.
Oral antivirals such as acyclovir are usually the treatment of choice.
So to review, HSV-1 more commonly has singular lip or mouth lesions, lays dormant in the
trigeminal nerve, and is transmitted by saliva.
While HSV-2 more commonly has multiple genital lesions, lays dormant in the sacral ganglia,
and is an STD.
However, you need to remember this is an oversimplification and there is a lot of overlap between these
2 viruses.
One last thing about herpes simplex is that HSV-1 is the most common cause of Viral Encephalitis.
We will cover this in more depth in the neuro videos, but I’ll touch on it briefly now.
It most often affects the temporal lobe.
This presents clinically with altered mental status, fever and in some cases seizures.
Immunosuppressed individuals are at greater risk for herpes encephalitis.
Lumbar puncture shows high lymphocytes in the CSF and imaging may show changes in the
temporal lobe.
Both HHV-1 & HHV-2 are also TORCH infections that can lead to neonatal herpes.
We will save that topic for a later video.
Varicella-Zoster Virus (VZV or HHV-3) is more commonly referred to as Chickenpox during
the primary infection or Shingles during the secondary infection.
Both of these present clinically with an erythematous (red) vesicular (fluid filled) rash that progressed
to scabs.
VZV is primarily spread by respiratory secretions, but can also be spread via direct contact
with a lesion.
Chickenpox (AKA Varicella) presents primarily in children when they are first exposed to
the varicella virus.
It affects non-immune hosts, meaning you can only get chickenpox once in your life if you
have an intact immune system.
Chickenpox is usually benign and primarily characterized by severe itchiness over the
entire body as the virus has spread through the blood.
The lesions start on the trunk and head, and then spread to the extremities.
Sometimes they describe the rash as being in a variety of stages at once which means
you can see red bumps, fluid filled vesicles, pustules and scabs at the same time.
here is a picture of chickenpox for you to look at.
The symptoms usually resolve over a couple weeks without any treatment.
However, calamine lotion, trimming finger nails, wearing gloves, and/or acetaminophen
are often used for symptomatic relief.
The individual also needs to be isolated to prevent spread of the contagious disease.
In recent years the Varicella Vaccine (AKA Chickenpox Vaccine) has been developed.
The vaccine drastically reduces the risk of getting the disease while also decreasing
the severity of the disease for those that still get it.
After chickenpox, the body is not able to completely remove the virus.
A small number of virus particles survive for decades in the sensory ganglia (primarily
the cranial and thoracic ganglia).
As the patient becomes elderly their immune system becomes weakened and the same varicella-zoster
virus can become reactivated to cause Shingles.
The skin lesions of Shingles (AKA Zoster) only occur in a single dermatome.
Therefore, the rash appears in “stripes” cross the skin that do not cross the midline.
This localized and well demarcated area of skin represents the specific area of skin
that is innervated by the sensory nerve that the virus has been reactivated in.
Here is a pic to review dermatomes from anatomy
Shingles can occur anywhere on the body, but the chest & back are the most common areas
affected.
The rash is grouped erythematous maculopapular lesions.
Shingles is primarily characterized by burning, pain, and fever, but there can also be a tingling
sensation in the dermatome even before the lesions arise.
The prodrome can also include non-specific symptoms like malaise, headache, and nausea.
Here are some pictures of shingles rashes.
The only pictures I could find are actually of pretty young people but remember this is
going to be much more common in elderly patients.
The symptoms usually resolve spontaneously over a couple weeks.
However, antivirals can be used if shingles is diagnosed early on early as it can lessen
the severity and duration.
Pain medications and antipyretics can be used for symptom control.
Postherpetic Neuralgia is when patient’s pain persists for months even after the rash
has resolved.
This pain can be very severe and difficult to treat.
There is also a vaccine for shingles called the Zoster Vaccine (Trade Name Zostavax).
It is a live attenuated vaccine that can be thought of as just a stronger version of the
Varicella Vaccine.
A onetime dose is recommended for adults starting at age 60.
Epstein Bar Virus (EBV or HHV-4 for short) is the primary cause of Infectious Mononucleosis
(AKA “Mono”).
The virus can be transmitted in saliva, hence the nickname “the Kissing Disease.”
It should be noted while sexual activity increases the risk of getting EBV, this is not an STD.
EBV infection is usually asymptomatic, but causes Mono in some individuals.
When symptomatic Mono primarily presents with flu like symptoms of fatigue, pharyngitis
(sore throat), headache, and lymphadenopathy (enlarged lymph nodes).
The lymphadenopathy may be accompanied by an exudative pharyngitis similar to strep
throat.
The symptoms last for a few weeks and are most commonly seen in teenage patients.
Mono is usually self-limited and no specific treatment is needed.
However, infected individuals should avoid contact sports (football, cheerleading etc.)
for about 1 month, because splenomegaly increases the risk of splenic rupture.
EBV is also associated with Nasopharygeal Carcinoma, Burkitt’s lymphoma and other
cancers.
EBV infects the B lymphocytes, mainly in the pharynx, and signals these B-cells to proliferate.
In response to these infected B-cells, cytotoxic CD-8 T-cells become activated and proliferate
also.
The white blood cell count for infected individuals is high and there is a high number of lymphocytes
or T Cells (>50% of the WBCs).
However, B-cells on the CBC are near normal as most of the B-Cells are in the lymph nodes
and cannot be seen in the peripheral blood.
In EBV infections the CD8 T-cells take on a characteristic appearance referred to as
“Atypical Lymphocytes” (AKA reactive lymphocyte).
They are larger and have more cytoplasm than normal appearing lymphocytes.
This finding should stick out as a buzzword for EBV, but remember that this finding is
not specific to Epstein bar.
Atypical lymphocytes can be seen on microscopy like in this picture
Cytomegalovirus (CMV or HHV-5) infects B cells and can be transmitted via saliva similar
to EBV.
CMV can also be transmitted sexually, through blood transfusions or organ transplants.
HHV-5 infection is primarily asymptomatic, but can cause Mono just like EBV.
Immunosuppression is a key risk factor for becoming symptomatic and symptoms are more
often seen in AIDs patients or following a transplant.
Immunosuppressed individuals may also have invasive Cytomegalovirus that most often causes
interstitial pneumonia.
Cytomegalovirus can cause atypical lymphocytes like EBV, but histologically CMV is more often
associated with “Owl Eyes.”
This owl eye sign is tough to distinguish from the Reed Sternberg Cells of Hodgkins
Lymphoma.
Here is a couples pictures of the owl eyes.
This appearance is caused by infected lymphocytes accumulating basophilic inclusions
CMV is also another TORCH infection, but we will save congenital CMV for a later video.
Both EBV and CMV can cause mono.
Therefore, differentiating between the two based solely on clinical scenario is difficult.
For cases of mono, a Monospot Test (AKA Mononucleousis Test or Heterophile Antibody Test) is used
to determine the causal virus.
This test is used to detect heterophile antibodies, a type of antibody that reacts with proteins
from other animals.
A sample of the patient’s serum is added to sheep or horse blood and if the heterophile
antibody is present in the patient’s blood it will cause the animal blood to agglutinate
(clump up).
A positive monospot test means the symptoms are caused by EBV and a negative means something
else is.
Thank you to Geoff Paterson from the UK for his generous donation on StompOnStep1.com
that helped make this video possible
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Thank you so much for watching and good luck with the rest of your studying.