Introduction

The most obvious diseases in history have been the plagues. These are acute epidemic infectious diseases with high mortality rates. In other words, they hit suddenly, spread quickly and kill lots of people. In this section you will find the best known plague, bubonic plague and one which was destroyed in the wild, but never cured, smallpox

Bubonic Plague

Causative Agent

Bacterium yersinia pestis

Primary Host

Rodents. Human plagues were most commonly associated with the black rat. Now rare in Britain, this rat is an excellent climber and tended to live in the rafters of buildings. That brought it into much closer proximity with humans than other species.

Spread by

The bite of rat fleas. The infection of humans was generally incidental to a plague among rats. A rain of rats, falling dead from the rafters, often preceded a human plague. The fleas were then forced to seek new hosts and were attracted to the nearby humans.

Fatality Rate

60%-70%

Birthplace

Probably the area of today’s border between India and China

Endemic Today

All continents except Europe and Antarctica

Earliest Known

First positive identification was the Plague of Justinian 542

First Significant in Britain

Possibly responsible for the plagues of 544, 664 and 682.

First positive identification at Weymouth in 1348

Major Outbreaks

From the fourteenth century, outbreaks occurred approximately once every generation until 1720, when the last major outbreak happened in Marseille.

Control Measures

The earliest measure was the trentino, a 30 day quarantine, imposed at Ragusa in 1377. As the disease never established a permanent presence in Europe, maritime quarantines provided a good first line of defence. The 1720 outbreak was attributable to passengers from an infected ship bribing their way past quarantine. Inland, control was more difficult and a wide variety of measures grew up. These included health passports for travellers, spy networks to warn of the disease, isolation of the sick, and the central management of medical and burial services. The administration of these measures, together with the record keeping needed to record the deaths and control the disposal of property, have been credited with being responsible for the growth of bureaucracy.

Decline

The disease disappeared from Europe from around the middle of the eighth century until the early fourteenth century. This was almost certainly due to the Muslim conquests and the subsequent loss of trade with the East.

There is no satisfactory explanation of the sudden decline of plague in the seventeenth century; there were only two major outbreaks in Europe after 1670. There is little doubt that maritime quarantine helped to block the importation of the disease. The widening of trade routes may also have helped by reducing dependence on trade with Asia. The development of an odourless, tasteless rat poison in the latter part of the seventeenth century may also have helped. However, this was also a period of low sunspot activity, lower global temperatures and advancing glaciers. Cooler weather was known to herald a reduction in the disease and may also have affected the routes of migratory rodents that carried it. A final factor may have been that recurrent plagues in central Asia had reduced the human and rodent populations to the point where the disease could no longer spread as it had before.

Situation Today

The disease can be treated successfully with antibiotics but local plagues still occur in areas with poor medical facilities.

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Smallpox

Causative Agent

One of two viruses; variola major or variola minor.

Primary Host

Exclusively a human disease. A single case of smallpox produced life-long protection to the survivors.

Spread by

Normally by inhalation of the virus, but also by direct contact with pus.

Fatality Rate

Variola major 25%-30%
Variloa minor 1%
The combined death rate in 1967 was 2 million per annum.

Birthplace

Probably the Indian sub-continent. It probably evolved from similar diseases in domestic animals.

Endemic Today

Extinct in the wild

First Significant in Europe

Until the sixteenth century, smallpox was considered an unpleasant, but not particularly dangerous, childhood disease. It is possible that it mutated to a more virulent form. An alternative explanation is that the more dangerous form already existed in Africa and was imported to Europe via the slave trade.

Control Measures

The first attempts at control followed the principles learnt from bubonic plague. However, the long incubation period made quarantine much less effective. In Asia and parts of Africa, the disease had long been the subject of variolation; the deliberate infection of healthy people with the pus taken from the pock marks of a sufferer. It was introduced to the West and first tried during the Boston, Massachusetts, outbreak of 1721. Variolation carried at 2.5% risk of death, but the disease killed around 14% of its victims in that outbreak. It provided a means of control, but at some risk. There were even outbreaks of smallpox caused by variolation.

It was later the same century that Edward Jenner noticed that patients who had caught cowpox were immune to smallpox. He then experimented with variolation, but using the pus from cowpox victims. He named the technique vaccination, which was derived from the Latin for cow. By 1801, more than 100,000 people had been vaccinated in England. By 1900 smallpox had been almost entirely eliminated in both England and Prussia. However, it was still a dangerous disease in many parts of the world. 

Elimination

Although there was no cure for smallpox, there was a way to eliminate it and in 1967 the World Health Organisation decided to attempt just that. It was realised that universal vaccination was not necessary. It was only necessary to locate every active case, a major task in itself, and to vaccinate every contact of that person. By 1972, smallpox had been eliminated from South America. By 1974, it had been eliminated from India. The last case of normally contracted variloa major was in October 1975 and in 1979, two years after the last case of variola minor the demise of smallpox in the wild was announced.

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