Smallpox is a highly contagious disease (it can be transmitted from one person to another) caused by the Variola virus. It killed around 30% of those who caught the disease, and left many of the survivors blinded or scarred.
|The Variola virus. © Centers for Disease Control, Public Health Images Library|
It has been one of the biggest killers in history. Its eradication in the late 1970s has been one of the greatest successes of international cooperation in public health.
The incubation period of smallpox - the time between infection and the appearance of symptoms - is between seven and 17 days. The first symptoms include a high temperature, headaches and tiredness.
Smallpox. © Centers for Disease Control, Public Health Images Library
Between two and four days after the first symptoms, the characteristic rash appears on the face or in the mouth. It then spreads to the arms, hands, legs and torso.
The rash begins as reddish bumps, which then become blisters and, finally, blister-like pustules.
When the pustules dry up, the resulting scabs leave scars – the so-called 'pockmarks' characteristic of smallpox survivors. For some, death follows as the virus multiplies in the blood.
The misery of smallpox
It is difficult to imagine the misery smallpox patients experienced, but the case notes of a patient who died during the last of the great epidemics in 1901 will give an idea.
||Patient seems very restless, wandering, at times got out of bed|
||Very restless all day, wanting to get out of bed. No sleep. Delirium (at intervals)...|
||Patient very restless all night. Got out of bed twice; delirious at times; cough troublesome. |
||Has been very troublesome all day/incline to be violent... No sleep. Cough troublesome.|
||Patient very noisy until 12.30 pm. Pulse very weak at times, has been in a drowsy condition since 4am.|
||Very restless early part of morn, not conscious since midday.|
||Patient died 12.50 am.|
Smallpox as a contagious disease
Smallpox can be transmitted by direct physical contact. A person with smallpox is most contagious after the rash appears and remains contagious until the last scabs dry up.
By this stage, patients are generally too ill to move around, so they are most dangerous to those in their home or hospital ward.
|Disinfecting clothes. © NMM|
The virus can survive up to a week outside the body, so contact with contaminated clothing or bed linen can also spread the disease.
|A cluster of smallpox cases in 1887. © NMM|
In most western countries, smallpox was endemic - it was around all the time and did not need to be introduced from outside. At regular intervals serious epidemics - major outbreaks affecting large numbers of people - would erupt.
A smallpox attack gave the victim lifelong immunity – a person who survived the disease could not catch it a second time. So, at any time, there were always plenty of immune people around.
Epidemics did not occur until there were enough susceptible people – those who could still fall ill. These would mostly be very young children, who always suffered most during epidemics.
This chart traces the probable course of smallpox infection during an outbreak in 1887. It shows just how easily smallpox could spread.
There is no cure for smallpox, but the most important breakthrough in fighting the disease was the development of vaccination. This involved giving a patient a weakened version of cowpox - a disease related to smallpox. This created a temporary immunity to smallpox, and saved the lives of millions of people worldwide.
|A public vaccinator at work, c. 1901. © NMM|