are large, brick-shaped,
enveloped -- in fact, they're the largest DNA
double-stranded viruses that we know of.
And you can see a scanning electron
microscope picture on the right.
It's a very prominent, bulky virus itself.
Its genome double-stranded DNA
is also linear in nature.
The virus is unusual because it carries
a mechanism to create its
own RNA polymerase.
And this is important, if you remember
back to normal viral growth,
in that it can replicate in the cytoplasm.
It does not have to borrow its
host cell's RNA polymerase.
Therefore, it can virally replicate
even more prominently,
which again is good because it's so big.
Only, again, when it lyses its
host cell does one get
the cytolytic infections, the
There are several different important
poxviruses that we need to consider.
The first, and perhaps the most prominent,
are the orthopoxviruses.
And you can see on the slide,
the specific species
variola virus, vaccinia virus, cowpox virus,
and even monkeypox virus.
So, as we'll see, these are associated with
smallpox or smallpox-looking infections
The parapox virus, are orf virus,
and bovine popular stomatitis virus.
Rarely do we encounter these
in clinical medicine,
although there have been some
reports of orf virus surfacing,
especially coming from countries in Africa.
The yatapox viruses are tanapox virus
and Yaba monkey tumor virus
limited primarily to the animal kingdom
and not things that are not viruses, which
we typically see in clinical medicine.
But we do see the molluscipoxvirus, or
the Molluscum contagiosum virus, MCV,
and what we'll talk a little bit more about
that at the end of this presentation.
So, let's start with the most prominent ones,
the ones which occupy everybody's
view and vision, both historically and in
terms of current bioterrorist attack.
And these are the variola, vaccinia,
and cowpox viruses.
The variola virus, the cause of smallpox,
is historically of incredible significance.
There are some fabulous literature
written about the journey to discover
and then eradicate the smallpox.
And eradication was successful in 1980,
with the potential exception of several
of the larger countries in the world
holding on to repositories of
virus, just in case.
So unfortunately, fears of
still exists and occasional attempts
to vaccinate first responders
have been conducted, actually,
in the recent future.
The cowpox virus was renowned for causing
similar pox-looking pustules,
but in dairymaids, the ones
who are milking the cows.
And in fact, it was
those lesions which were
harvested by Dr. Jenner
to create the first vaccine
Now, it was dirty.
It was messy, but it was actually relatively
successful, and one of the first examples
of successful vaccination strategies which
we know about in medical history.
The smallpox vaccine
is able to use live, but attenuated, meaning
process to remove any virulence.
Vaccinia virus, and this vaccine,
as I mentioned, has been re-initiated,
for military or personnel or healthcare
personnel, first responders,
because of the concern for bioterrorism.
The images which you see on
this slide, the lower right
represents the site of primary vaccination
with vaccinia virus.
Yeah, it's ugly, it's messy,
and it weeps active vaccinia virus
for at least several weeks, hence, it's
typically covered by, in this case, a band aid.
The image on the upper right
shows extensive lesions, not just
smallpox, but of a vaccinia reaction.
That is a patient who, for whatever reason,
developed viremia related
to the vaccination,
and developed the equivalent of a smallpox,
but carried out by vaccinia.
And such vaccine reactions occurred
in a cluster of cases after the vaccine
recently in the States.