Society, the Individual and Medicine

The Historical Decline in Infectious Diseases   To Infectious Disease theme page

1. Core Knowledge:

Infectious disease mortality decreased rapidly through much of the 20th century, until around 1980 when a significant turn-around began to occur. Between 1980 and 1992 the death rate from infectious diseases in the USA increased by 58% (this figure refers to people for whom the primary cause of death was an infectious disease). Since then we have become increasingly nervous about the possibility of a new pandemic, and tyhe importance of public health measures is widely recognized.

It is easy to be over-confident about medical advances; infectious agents are diverse, can travel and mutate, and will always challenge our defences against them.  The issue mirrors the ecological challenges posed by zebra mussels, spruce budworms and other beetles that continually threaten plant species.  We should never forget the potential dangers: the influenza pandemic of 1918 and 1919 killed more than 20 million people worldwide (including 500,000 in the U.S.).  More than all of the wars in the century.

to modes of transmission for infectious disease


2. Nice to Know:

The "End" of Infectious Diseases? Microscope

In the years of optimism following World War II, many believed that humans were winning the long war against infectious microbes.  Antibiotics could cure bacterial diseases such as TB and typhoid fever.  Diseases of childhood such as polio, whooping cough, and diphtheria could be conquered through vaccination.  Coupled with earlier improvements in urban sanitation and water quality, vaccines and antibiotics dramatically lowered the incidence of infectious diseases.  It became plausible to imagine a world in which infectious pathogens would no longer prey on humanity.
Link to facts & figures: on impact of immunization.
Excellent web site on the History of Immunization

As it turned out, the optimism was premature:


By the early 1990s, health experts no longer believed that the treat of infectious diseases was receding.  The growing concern was expressed in a 1992 report by the Institute of Medicine of the U.S. National Academy of Sciences called Emerging Infections: Microbial Threats to Health in the United States.  This emphasized the intimate links between U.S. health and international health.  It described the factors that contribute to disease emergence, including societal changes and the ability of pathogens to evolve and adapt.  It concluded that emerging infectious diseases are a major threat to health, and it challenged governments to take action.

Why Are Infectious Diseases Emerging?

The 1992 report defined emerging infectious diseases as those whose incidence has increased within the past two decades, or may increase in the near future.  Modern social, economic, demographic and environmental conditions favor the spread of infectious disease:

CDC web site on Emerging Infectious Diseases ("EIDs").

The Impact of Public Health

We should naturally celebrate the awesome impact of the nineteenth century microbiological discoveries and the era of immunization that followed. But there is another reality: infectious diseases were declining long before the development of effective therapy and before immunizations became widely available.

Here is an historical view of deaths due to measles.  The decline after the first World War was due to public health measures (case reporting, quarantine, etc) more than immunization.  The immunization came in at the very end, as a finale to the prevention story.

Decline in measles mortality, 1850 to 1980

Here is a similar diagram for whooping cough ... And for tuberculosis
Decline in whooping cough mortality, 1860 to 1960 TB mortality decline, 1840 to 1960.

Updated January 26, 2015