Microbiology and Immunology

Epidemics and pandemics WORLD OF MICROBIOLOGY AND IMMUNOLOGY

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conditions. Inadequate sanitation has and continues to be the

breeding ground for the bacteriaand virusesthat can sweep

through populations. The gathering of people in the burgeon-

ing cities of seventeenth and eighteenth century Europe lead to

a series of epidemics. These included typhus, typhoid fever,

plague, smallpox, dysentery, and cholera. Outbreaks are less

of a problem in modern day cities, due to better sanitation

conditions and standards of housing. However, in underdevel-

oped areas of the world, or even in the developed world where

sanitation and housing conditions are deficient, such diseases

are still present.

Epidemics and pandemics can be so devastating that

they can alter the course of history. An example is the Black

Plague that spread through Europe and Britain in the seven-

teenth century. An estimated one-third of the population of

Europe was killed, and cities such as London became nearly

deserted, as those who could afford to do so fled the city. In

the Crimean War (1853–1856), more than 50,000 soldiers died

of typhus, while only 2,000 soldiers were actually killed in

battle. As a final example, the spread of the plague to the New

World by contaminated blankets aboard French sailboats that

docked at Halifax, Nova Scotia, in 1746, lead to the decima-

tion of the aboriginal inhabitants of North America.

Within the past several decades, there has been an

increasing recognition that disease that were previously

assumed to be of genetic or other, nonbacterial or nonviral ori-

gin are in fact caused by microorganismshas lead to the

recognition that there may be an epidemic or pandemic or mal-

adies such as stomach ulcers and heart disease. These diseases

differ from other bacterial and viral epidemics and pandemics,

because they do not appear and fade over a relatively short

time. Rather, the stomach ulcers caused by the bacterium

Helicobacter pyloriand the heart disease caused by the reac-

tion of the immune system to infection by the bacterium

Chlamydiaare so-called chronic infections. These infections

are present for a long time, essentially causing a non-stop pan-

demic of the particular malady.

See alsoBacteria and bacterial infections; Bubonic plague;

Flu, Great flu epidemic of 1918

A painting depicting the effect of an epidemic (in this case, the plague in Florence, Italy).

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