Professor Alimuddin Zumla
Professor Alimuddin Zumla Director
of the Centre for Infectious Diseases at the University College
London celebrates the global eradication of the disease in 1977
with a cautious hint on how the forgotten horrors could be revived
by use of the virus as a biological weapon.
Historical accounts of smallpox date back
to 1580 BC in Egyptian mummies. Over centuries, smallpox was apparently
a devastating illness characterised by extensive, profuse vesicular
skin rashes and with a high mortality rate. Survivors were left
with severe disfiguring facial scars. Smallpox was a disease with
characteristic clinical signs. It caused dramatic and disastrous
epidemics which became the subject of myths and superstitions
around the world. The human smallpox virus was one of the most
fatal of all viral infections. If a sufferer survived the attack,
a lifelong immunity ensued. A textbook printed in 1988 by the
World Health Organisation in 1988
(ISBN:9241561106) is one of the most comprehensive available on
the subject. While hard copies are not available, it is viewable
on the internet at website. www.who.int/emc/diseases/smallpox/smallpoxeradication.html.
Smallpox in Africa
The earliest presumptive evidence of smallpox anywhere in the
world is in Egyptian mummies over 3000 years old. Later, smallpox
swept along the North African coast during the great expansion
of Islam in the 8th century. The disease became endemic around
the Mediterranean region. The slave trade in the 18th and 19th
centuries provided excellent conditions for the spread of smallpox.
With traders penetrating deep into the interior, the overland
caravans carried smallpox far and wide into central Africa. The
Portuguese established a settlement in Luanda, Angola in 1484
and probably introduced smallpox into the area shortly after that.
Over the next two centuries, smallpox and
the slave trade combined to take a terrible toll on the population.
In 1713 smallpox was imported into South Africa through a ship
that docked at Cape town on a return trip from India. In the 19th
century, Arab slave trade expanded from the east coast ports into
central Africa. Smallpox was brought into Uganda by slave caravans
in the 1840s. Meanwhile, smallpox continued to be a severe endemic
disease in coastal towns in north
Africa. Six epidemics were reported in Ethiopia and Sudan: in
1811-1813; 1838-1839; 1865-1866; 1878-1879; 18885-18887 and 1889-1890.
Smallpox in Southern Africa
In 1967 when the World Health Organisation (WHO) smallpox eradication
programme began, the disease didn't appear to be a major problem
throughout southern Africa. Political problems made it difficult
for WHO to co-operate with governments. Only 4 countries with
a population of 10.4 million in 1970 were member-states of WHO
with full voting rights. Angola and Mozambique were
pre-occupied with their respective civil wars. Nevertheless rapid
results were achieved in central and western Africa and steady
progress occurred in eastern and southern Africa. By 1976 the
only remaining endemic country in Africa was Ethiopia and Somalia.
By the end of 1977 smallpox had been totally eradicated in Africa.
Indeed, smallpox is one of the few infectious
diseases that has been eradicated globally. There was one host,
one virus and one vaccine and thus the eradication of smallpox
was a straightforward matter. The success of this eradication
programme was based on several factors:
1. Human beings were the only hosts.
2. An effective vaccine inducing solid immunity was available
3. Governments were committed to the vaccination programmes. This
was backed up by the WHO's search and containment campaigns where
cases were isolated and contacts were traced and vaccinated. The
last case of endemic smallpox occured in Somalia in 1977 and eradication
of the disease was declared in 1980. The world has been free of
small pox for the past two decades and the eradication campaign
is heralded as one of the most successful carried out by the WHO.
A recent review in the New England Journal of Medicine gives a
succinct updated summary of the clinical features and diagnosis
of smallpox (Breman et al,2002). The pox viruses are double-stranded
DNA molecules of 130-375 kb pairs and are shaped like bricks on
the electron micrograph pictures measuring 250 x 200 x 300 nm.
Due to strain variation, two clinical forms of the disease are
expressed: Variola major causes the more serious form
of the diseases and forms the majority of cases. Variola minor
causes a less sever form of smallpox. The virus enters the respiratory
tract and seeds onto the mucous membranes and spreads into the
regional lymph nodes.
After a brief period of viraemia there is
a latent period during which time the virus multiplies in the
reticuloendothelial system. During this prodromal phase mucous
membranes in the mouth and pharynx are infected. The virus then
enters the capillary epithelium of the dermal layer in skin and
mucous membranes, leading to the development of papules, vesicles
and pustules. The lesions contain abundant viral particles. Since
every organ of the body becomes infected with the virus the disease
is systemic. The urine, saliva and tears of the sufferer are also
teaming with virus particles. The incubation period for smallpox
is 7 to 17 days (mean 10 to 12). The prodromal phase is non-specific
and lasts for two or three days and is characterised by a headache,
backache, and fever beginning abruptly.
The skin rash begins as a small reddish macule,
which becomes a papule with a diameter of around 2-3mm over a
period of one or two days. After an additional one or two days
the papules become vesicles with a diameter of 2 to 5mm. The lesions
occur first on the face and extremities but gradually cover the
whole body. Pustules of around 4-6mm in diameter develop about
four to seven days after the onset of the rash and remain for
up to to eight days. If the patient is still alive, the lesions
then umbilcate and then crust which then falls off leaving a scar.
Death from smallpox is due to toxaemia, immune complexes and hypotension.
After a smallpox, pockmarks or pitted lesions are seen in 65-80
per cent of survivors.
The diagnosis of smallpox is usually a clinical one. As the skin
manifestations are similar to those of other cutaenous viral exanthemata,
clinically the smallpox can be mistaken with many skin illnesses
such as severe chickenpox, monkeypox, molluscum contagiosum, severe
herpes, simplex infections and drug skin reactions. Clinical samples
for virological confirmation (by several methods including viral
culture, immunoflourescence, ELISA and polymerase chain reaction)
should be handled very carefully and be processed in category
4 laboratory where staff members have been vaccinated.
Significance of smallpox today
Given that smallpox disappeared worldwide over two decades ago,
its significance in public health today is nought. However, the
disease has of late aroused extensive interest and debate throughout
the world due to its potential as a biological weapon. Smallpox
is highly contagious and could spread rapidly by direct contact
with an infected person and could potentially kill millions. Following
the attack on the New York twin towers in September 2001 the media
has reviewed the threats of biological warfare, causing much anxiety
to the public.
Strategies to prevent smallpox threat
In light of the growing threats of bio-terrorism and the fragile
nature of global politics, developing public health strategies
to counter bio-terrorism threats from smallpox is a high global
priority. In the event of an emergency consequential upon a smallpox
outbreak, there are insufficient stocks of smallpox vaccine (vaccinia
virus) available to vaccinate the population of the USA or UK,
let alone everyone globally.
What to do if there is a smallpox
Any clinical suspicion of a case of smallpox is a public health
emergency and is of international concern. When a health worker
suspects smallpox, the case must be reported immediately to relevant
authorities who should immediately get in touch with the World
Health Organization Department of Communicable Diseases in Geneva,
Switzerland or the Centres for Disease Control (CDC) in Atlanta,
USA. The patient should be immediately isolated and contacts be
identified. The contacts and all health personnel should be vaccinated
as soon as possible. All governments and health systems must be
prepared for a smallpox outbreak.
Breman JG, Henderson DA. Diagnosis and management of smallpox.
New England Journal of Medicine 2002; 346: 17: 1300- 1308.
Fenner F, Hendersen DA, Arita I, Jezek Z,
Ladni ID. Smallpox and its eradication. WHO CSR website: www.who.int/emc/diseases/smallpox/Smallpoxeradication.html
Kaplan J. CDC's startegic plan for bioterorrism
preparedness and response. Public Health Report 2001;116 suppl
For more information Email: firstname.lastname@example.org
Table 1: A classification of clinical types of smallpox
Variola sine eruptione
Flat type Pustules remain flat:
pustular skin lesions
Three sub types:
a) Confluent: confluent rash on face/forearms
b) Semiconfluent: semiconfluent rash on face, discrete elsewhere
c) Discrete: areas of nomal skin between pustules, even
As above but has an accelerated course
Fever without rash caused by variola virus
usually confluent Usually fatal
Widespread haemorrhages in skin and mucous membranes.
a) early with purpuric rash -always fatal
b) late, with haemorrhages into base of pustules -
on Ramchandran Rao (1972)