Before its eradication, smallpox (variola) was an
acute, highly contagious, exanthematous viral infection.
contains a double-stranded DNA and produces a typical plaque, or
“pock”, when cultured on chorioallantoic membrane of embryonated
chicken eggs. Visit:
Herpes Zoster Virus (Shingles)
Herpes Simplex Virus Infection
Since Jenner’s pioneering work in 1796,
a similar virus - vaccinia, the causative agent of cowpox - has been used for
“vaccination” to protect against small pox.
Smallpox was evidently an ancient disease; a rash
resembling smallpox was found in the mummified remains of the Egyptian
Pharaoh Ramses V, who died in 1160 BC.
The disease once had worldwide
distribution in both urban and rural areas, afflicting persons of both
genders and all ages, but particularly children.
In 1967, the World Health Organization
began its uniquely successful campaign to eradicate smallpox.
By then, smallpox had already been
controlled in most developed countries but was still endemic in the
less developed world.
In 10 years the vaccination campaign
eradicated the disease.
The successful eradication of smallpox
depends on several factors, including the permanence of immunity
following vaccination, the stability of the smallpox virus (in
contrast to the genetic instability of
viruses and many others), and the lack of an animal reservoir for the
Smallpox was transmitted in respiratory droplets and
almost always involved face to face contact.
The virus infected the oropharynx or nasopharynx, multiplied in lymphoid tissue of the upper
respiratory tract for about 2 day period of viremia and then entered a
4 to 14 day “latent” period, when it was undetectable in the blood and
was assumed to be multiplying in the reticuloendothelial system.
another 1 or 2 day period of viremia, there was a 2 to 4 day prodrome
of nonspecific febrile symptoms.
The prodrome was followed by characteristic eruption
of smallpox, which evolved through several stages, beginning as macules,
then progressing over a 1 to 2 week period through papules, vesicles,
The pustules umbilicated within 2 weeks, and desiccated
(“crust”) to form scabs.
The scabs, which contained the smallpox
virus, usually sloughed from the skin, thereby creating fresh, pitted
Pitting or pockmarking was most common over facial areas that
have numerous sebaceous glands.
In the most severe form, black,
“hemorrhagic small pox”, which was almost always fatal, there was
bleeding into the vesicles and pustules.
Histologic features of the
earliest stage of the rash included hyperemia, swelling of capillary
endothelium, and perivascular infiltrates of lymphocytes and
histiocytes in the upper dermis.
Multiloculated vesicles developed by
rupture of the membranes between degenerating epithelial cells.
was ballooning of cells in the lower levels of the stratum spinosum,
and some degenerating cells fused into giant cells with two or more
Eosinophilic intracytoplasmic inclusion bodies (Guarnieri’s
bodies) were prominent in ballooned epithelial cells.
Secondary bacterial infections during the pustular
stage led to complications such as keratitis, laryngitis,
encephalitis, osteomyelitis, and orchitis.
Viral keratitis and secondary bacterial
infections of the eyes were frequent complications.
Many patients in Asia developed corneal
ulcerations, and smallpox was usually the primary cause of blindness
during epidemic periods.
In pregnant women, the disease
frequently caused abortion.
vaccination in the preoutbreak setting is contraindicated for
persons who have the following conditions or have a close contact
with the following conditions:
history of atopic dermatitis (commonly referred to as eczema),
irrespective of disease severity or activity; 2) active acute,
chronic, or exfoliative skin conditions that disrupt the
epidermis; 3) pregnant women or women who desire to become
pregnant in the 28 days after vaccination; and 4) persons who are
immunocompromised as a result of human immunodeficiency virus or
acquired immunodeficiency syndrome, autoimmune conditions, cancer,
radiation treatment, immunosuppressive medications, or other
immunodeficiencies. Additional contraindications that apply only
to vaccination candidates but do not include their close contacts
are persons with smallpox vaccine-component allergies, women who
are breastfeeding, those taking topical ocular steroid
medications, those with moderate-to-severe intercurrent illness,
and persons aged < 18 years. In addition, history of Darier
disease is a contraindication in a potential vaccinee and a
contraindication if a household contact has active disease.