The Economic Consequences of the Black Death
Paolo Malanima
Contact with other animals was the cause of the worst infectious illnesses
that have affected the human species in past agrarian societies. 
Various strains of influenza, smallpox, malaria, plague, measles, and cholera were provoked by infections which first affected domestic animals or those non-domestic species with
which humans came into contact, such as mice, fleas or lice and were then transmitted from animals to humans and from humans to other animals. In pre-modern agrarian societies, between two thirds and three quarters of deaths were caused by infectious diseases. 

Only in recent times has what is defined as an epidemic transition taken place. In 18th–19th century Europe there was a shift from illnesses transmittable from one person to another to degenerative non-infectious diseases. The mortality rate has depended to a lesser degree on bacteria and viruses and on the inter-specific struggle among different animal species.

Great epidemics mark the agricultural world of the past; from Neolithic times
onwards. The formation of much denser societies with respect to those of hunters
and gatherers, and daily contact with domestic animals are at the origins of serious
epidemic infections which have accompanied humans for 10,000 years. Among
these are infections of the digestive system – typhoid and paratyphoid fevers, dysentery, diarrhoea, cholera --; infections of the breathing apparatus, transmitted through the air -- smallpox, diphtheria, measles, influenza --: infections of the reproductive system -- syphilis and venereal diseases in general --; diseases introduced into tissue and into the blood stream deriving from insect bites -- plague, typhoid fever, yellow fever and malaria --.

Density and mobility of population, and poor diet have often been regarded as determinants of these epidemics. The relationship between population and resources plays an important role, but chance also plays a role in the spread of infections.

The existence of the plague in Europe from the 14th until the 18th century has
been discussed in recent years. Although some differences exist between the medieval disease and the one directly observed by modern epidemiologists, the prevailing opinion is still that the Black Death was actually caused by plague.

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