Patterns of movement
Many diseases, particularly those that depend on animals or insects for transmission, occur mainly in certain areas. Such diseases are called 'endemic' to those areas and - in centuries past - they rarely travelled far. Other diseases moved slowly by land, carried by people, animals or goods. Only through sea travel could diseases move to new continents.
The international movement of diseases
Most of the best known diseases seem to have originated outside Europe. It is likely that smallpox and plague reached Europe from Asia, while syphilis probably came from the Americas. Other diseases came to Europe from the Tropics.
However, the Europeans - the world's most active traders, conquerors and settlers - carried many diseases across the world. They took smallpox to the Americas, the Pacific, Australia and parts of Africa and Asia. They also took syphilis and yellow fever back to Europe.
The Black Death
|Woodcut of early German ships, circa 1530. © NMM|
In all these movements, sea travel was crucial, and ports were the gateways through which disease could enter.
The Black Death of the 14th century came into Britain through the eastern ports that traded with Europe. The bacteria that caused the disease were carried here by fleas, either on the clothing of travellers or on imported cloth. Once here, the disease spread inland by river shipping or by people moving on foot or by horse-drawn wagons.
The great cholera epidemic of 1831-32 entered Europe through the ports, and struck American ports in 1833.
|London Docks, looking west, 1831. © NMM|
In the time it took for cholera to spread any distance inland, ships had carried the disease to many new ports.
Ships and disease today
At the end of 2003, an incident on board the P&O cruise liner Aurora demonstrated how ships can still carry disease. It is believed that a passenger embarked at Southampton carrying the highly infectious Norwalk virus.
By the time the Aurora reached the Mediterranean, more than 500 people on board had gone down with the virus. Fortunately, the virus was contained before it could infect anyone on shore.