1. By
Shireen Abdulrahman
Biochemistry of viruses course
[Biochemistry Department]

2. 'Could it not be contrived to send smallpox among
these disaffected tribes of Indians? We must use
every stratagem in our power to reduce them.‘
Sir Jeffrey Amherst, the Commander-in-Chief of the British forces in North America 1763

3. 'I will try to inoculate the [Native American tribe]
with some blankets that may fall in their
hands, and take care not to get the disease myself.‘
Colonel Henry Bouquet, British forces in North America 1763

4. Smallpox decimated the Native Americans, who had
never been exposed to the disease before and had
no immunity.

5. In the 1980s, the Soviet Union developed variola as an
aerosol biological weapon and produced tons of
virus-laden material annually intended for
intercontinental ballistic missiles.

6. Smallpox is considered one of the most serious
bioterrorist threats.

7. An estimated 300 million people died from smallpox in the
20th century alone.
As the world's population grew, and travel increased, so the
virus that Edward Jenner called the "speckled monster"
grasped every opportunity to colonize the world.
People struggled to find ways to battle with smallpox.
It was also potentially one of the most devastating
biological weapons ever conceived

8. Smallpox is an acute, contagious disease unique to humans, caused by
either of two virus variants, Variola major and Variola minor.
The disease is also known by the Latin names Variola or Variola
vera, which is a derivative of the Latin varius, meaning
"spotted", or varus, meaning "pimple".
The term "smallpox" was first used in Europe in the 15th century to
distinguish variola from the "great pox" (syphilis).

9. Smallpox is believed to have emerged in human populations about
10,000 BC. The earliest physical evidence of smallpox is probably the
pustular rash on the mummified body of Pharaoh Ramses V of Egypt.
Traders carried the disease from Egypt to India during the 1st
millennium BC. From there it swept into China in the 1st century AD
and reached Japan in the 6th century
Returning crusaders provided a way for smallpox to spread through
Europe in the 11th and 12th centuries.

10. After vaccination campaigns throughout the 19th and 20th
centuries, the WHO certified the eradication of smallpox in 1979.
The last naturally occurring case of smallpox (Variola minor) was
diagnosed on 26 October 1977.
Smallpox is one of the two infectious diseases to have been
eradicated, the other being rinderpest, which was declared
eradicated in 2011.

11.  Variola has 2 predominant variants, major and minor
 Variola major —is a serious illness with a mortality rate according
to the CDC of 30% or more, in unvaccinated people, while Variola
minor — is a milder infection with a mortality rate of less than 1%
 During the era of naturally occurring smallpox, several variations of
variola major disease were recognized.

14. Smallpox Signs and Symptoms
The symptoms of smallpox begin with high fever, head and body
aches, and sometimes vomiting.
A rash follows that spreads and progresses to raised bumps and pus-
filled blisters that crust, scab, and fall off after about three
weeks, leaving a pitted scar.

18. Figure : Progression of smallpox in humans

19. Transmission can happen in one of several ways:
 Face-to-face contact
 Direct contact with infected fluids and contaminated objects
 Through the air
 The virus can cross the placenta, but the incidence of
congenital smallpox is relatively low.
 Smallpox transmission does not occur through animals or
insects.

20.  Physical exam for signs and symptoms of smallpox. This will
include a skin and mouth exam to look for the smallpox rash.
 If there is a moderate or high suspicion of smallpox, the doctor
may order certain lab tests.
 Tests may only be conducted in specially protected
laboratories, known as "Biosafety Level 4" labs (BSL-4).

21.  PCR and restriction fragment length polymorphism (RFLP)
analysis are used to identify the specific strains
 ELISA and serologic tests measure the variola virus-specific
immunoglobin and antigen to aid in the diagnosis of the virus.
 Immunohistochemistry and electron microscopy
 The origin of the virus may be traced by genome analysis of
the virus.

22.  In order to precisely diagnose a smallpox infection, virus must be grown on
chorioallantoic membrane - a vascular membrane found in bird eggs - and
then have the lesions examined.
At the microscopic level, Poxviruses form cytoplasmic inclusions, such as
Guarnieri bodies in virus-infected epidermal cells.
The virus appears as pink blobs when stained with eosin and hematoxylin.

23. Figure : A photograph revealing smallpox virus pocks on the
chorioallantoic membrane of a developing embryonic chick.

24. Before a smallpox diagnosis is made, your healthcare
provider will consider other illnesses that can mimic the signs
and symptoms of smallpox. Some of these illnesses include:
 Chickenpox
 Monkeypox
 Herpes zoster (also called shingles)
 Adverse reaction to medications
 Contact dermatitis
 Erythema multiforme
 Hand, foot, and mouth disease

25. Figure: Rash in smallpox vs. chickenpox

26. Figure: This is a chickenpox scab (left), and smallpox scab (right) viewed
from above as a demonstration in comparative morphology.

27.  Smallpox is caused by infection with variola virus, which
belongs to the genus Orthopoxvirus.
 The organism got its name from the Latin
word varius meaning spotted, or varus meaning “pimple”.
 Variola virus infects only humans in nature.

28.  Both enveloped and unenveloped virions are infectious.
 Variola major causes smallpox and Variola
minor causes alastrim.
 Infection with either variola major or variola minor confers
immunity against the other.

29. Figure : Variola virus, the agent of human smallpox.

30. Variola virus is a large brick shaped virus with a measurement
of 302 to 350 nm by 244 to 277 nm, which consist of single
linear double stranded DNA.
Its genome consist of 186 kbp and contain a hairpin loop at
each end.
The hairpin loop at each end consists of 530 bp fragments.

31. They have 187 closely spaced open reading frames specifying
putative major proteins contain more than or equal to 65
amino acids.
The complete DNA (deoxyribonucleic acid) sequence of two
closely related variola virus (VARV) genomes was published
in the early 1990s.

32. Figure : Variola virus genome bp, base pair; ORF, open reading frame; VARV, variola virus.

33.  Variola viruses are DNA viruses with virions consist of a surface
membrane, a core, and lateral bodies with or without an envelope.
 During their life cycles variola produces extracellular and
intracellular particles. The infection is caused by the extracellular
particles.
 The capsid of virus is enveloped and virons mature naturally by
budding through the membrane of the host cell.

34. Figure: Variola cell structure

35. Poxviruses are unique among DNA viruses in that they replicate in
the cytoplasm of the cell rather than in the nucleus.
In order to replicate, poxviruses produce a variety of specialized
proteins not produced by other DNA viruses, the most important of
which is a viral-associated DNA-dependent RNA polymerase.

36. Virus particles land on the cell surface and are taken into the cell.
The genetic information (DNA) of the virus is released into the
cell and begins to make copies of itself.
These new DNAs are taken into the developing spherical viral
particles and the particles mature internally and in so doing adopt
a more block like appearance.

37.  Most will remain in the cell
as Intracellular Mature Viruses, (IMV) and will be released
when the cell bursts.
 However, some of the virus particles will obtain a second
wrapping of host cell membrane and this occurs at the trans
Golgi.
 These double wrapped particles are
called Intracellular Enveloped Viruses (IEV).

38.  Some IEVs push through the cell's plasma membrane and
remain attached to the cell surface. These are called Cell-
associated Enveloped Viruses (CEVs).
 Others that push through the membrane are released and are
called Extracellular Enveloped Viruses (EEVs).

39. Figure: Orthopox virus replication

40.  This organism is transmitted among humans primarily by inhalation
of virus or by droplets from oral, nasal or pharyngeal mucus of an
infected person.
 After the virus enters in the human body through respiratory tract, it
grows on the mucous membrane and then spreads to the lymph
nodes where it multiplies and then finally enters the blood stream.

41. Pathology
After entering the blood stream the virus invades internal organs and
skin.
The time frame for the incubation of small pox is 10 to 12 days.

42.  There is no proven treatment for smallpox, but research to evaluate
new antiviral agents is ongoing.
 Laboratory studies suggest that the drug cidofovir may fight against
the smallpox virus.
 Patients with smallpox can benefit from supportive therapy such as
wound care and infection control, fluid
therapy, possible ventilator assistance and antibiotics for any
secondary bacterial infections that may occur.

43.  Vaccinia immune globulin (VIG) can be offered to persons
exposed to smallpox as a prophylaxis.
 Vaccination within three days of exposure can aid in the
treatment by preventing or significantly lessen the severity of
smallpox symptoms in the vast majority of people.

44. Prevention of smallpox rests on two pillars:
1. Vaccination
2. Isolation of patients if they develop fever.

45.  The smallpox vaccine is made from a virus called vaccinia which is
a “pox”-type virus related to smallpox.
 The smallpox vaccine contains the “live” vaccinia virus—not dead
virus like many other vaccines.
 Also, the vaccine can have side effects. The vaccine does not
contain the smallpox virus and cannot give you smallpox.

46.  The only smallpox vaccine currently licensed by the Food and Drug
Administration is Dryvax.
 The vaccine was first approved in 1931, and the existing lots were
manufactured in the 1970s and early 1980s and stored frozen

47.  Smallpox vaccination provides high level immunity for 3 to 5 years
and decreasing immunity thereafter.
 If a person is vaccinated again later, immunity lasts even longer.
 Historically, the vaccine has been effective in preventing smallpox
infection in 95% of those vaccinated.

48.  The vaccine is given using a bifurcated (two-pronged) needle that
is dipped into the vaccine solution.
 The pricking of the skin will cause a sore spot and one or two
droplets of blood to form.
 The vaccine usually is given in the upper arm.
 If the vaccination is successful, a red and itchy bump develops at
the vaccine site in three or four days.

49. Figure: Smallpox vaccination site, Day 4 through 21.

50.  After vaccination, it is important to follow care instructions for the
site of the vaccine.
 Because the virus is live, it can spread to other parts of the body, or
to other people.
 The vaccinia virus (the live virus in the smallpox vaccine) may
cause rash, fever, and head and body aches.
 In certain groups of people, complications from the vaccinia virus
can be severe.

51. Smallpox is considered one of the most serious bioterrorist
threats.
It was used as a biological weapon during the French and
Indian Wars, (1754 to 1767) when British soldiers
distributed smallpox-infected blankets to American Indians.
 In the 1980s, the Soviet Union developed variola as an
aerosol biological weapon and produced tons of virus-laden
material annually intended for intercontinental ballistic
missiles.

52. Several factors contribute to the concern about the use of
smallpox as a biological weapon:
 Variola can spread from person to person.
 There is no widely available or licensed treatment for the disease.
 It has a high fatality rate.
 Variola is relatively stable as an aerosol.
 The infectious dose is small.

53.  Since routine smallpox immunization ceased in the United States in
1972 and in all other countries by 1983, the global population is
extremely vulnerable to the disease.
 Most of the world’s population has never been vaccinated or was
vaccinated so long ago that immunity to smallpox has waned.
 Because there are no symptoms at the time of exposure, a covert
release of variola may not be detected until sick people begin
showing up at doctor's offices and hospitals.