Introduction

Epidemic diseases are those that affect large numbers of people in one area at the same time. This section only deals with influenza, which has the dubious distinction of killing more people in a single year than any other cause in history.

Influenza

Causative Agent

Influenza is a viral disease.

Primary Host

Humans and domestic animals, particularly pigs and fowls.

Spread by

Inhalation of the virus.

Fatality Rate

Normally around 1%. In absolute terms, 1% of those infected by a pandemic can be a very large number.

Birthplace

Unknown.

Endemic Today

Globally

Earliest Known

It was first described by Hippocrates in 412 BC. There is no further definite record of the disease before an epidemic in Europe in 1510.

Major Outbreaks

There were major outbreaks in 1510, 1557 and 1580, the last being a pandemic, before a lull in activity through the seventeenth century. In the eighteenth century there were at least three, and possibly five, pandemics in Europe, the worst being in 1781-2. In the nineteenth century there were pandemics in 1830-1, 1833 and 1889-90. It was known as Russian flu in this last outbreak.

Things changed dramatically in 1918 when another pandemic, almost certainly spread by troops returning from World War 1, swept the world. What made this outbreak different was that, instead of killing the very young and the very old, it was killing people in the prime of their life. It also had a remarkable tendency to initiate pneumonia in its victims. Modern estimates put the death toll from that outbreak at around 30 million people, more than had died in World War 1.

Further pandemics occurred in 1957 (Asian Flu) and 1968 (Hong Kong Flu) and between them they killed 1.5 million people.

Control Measures

Vaccination is practiced in Britain among those identified as being most at risk. The surface of the influenza virus is unstable and it frequently mutates, even during the course of an epidemic, which makes any immunity gained by either vaccination or infection purely temporary. There are also anti-viral drugs that may prove to be effective in preventing or reducing the severity of the disease.

Situation Today

The changeability of the virus contributes to the cyclic nature of the pandemics. World Health Organisation centres monitor the disease and the WHO makes recommendations to the manufacturers about the composition of the next year's vaccine.