Microbes in Motion: Touring World History

Editor’s note: First published in 2004, this feature has gained new currency in light of the current COVID 19 crisis. In particular, it provides our readers with a historical perspective on infectious diseases and pandemics.

There is overwhelming historical evidence that contact between previously isolated populations and ecosystems — or their integration into larger units — has created major evolutionary discontinuities and often exacted a tragic disease toll.

Microbial disasters in antiquity

William H. McNeill has observed that the expanding Roman Empire was repeatedly afflicted by strange maladies originating in the provinces. During the times of the Roman Republic alone, there were reportedly at least 11 microbial disasters.

A major epidemic struck the city of Rome in 65 C.E., but that paled in comparison with a widespread pandemic that began to sweep through the entire empire in 165 C.E.

Mortality in this latter plague was heavy: It is estimated that one-quarter to one-third of those coming down with the disease died.

Rise of commerce

In more recent history, contacts between expanding European populations and those in other parts of the world had similarly serious disease ramifications.

By the middle of the 14th century, many of the small kingdoms of Western Europe had begun to increase commerce, not only with each other, but with countries of the Orient — courtesy of expanding trade routes between Europe and China.

Black Death

During this period of economic growth, urban expansion and increasing trade, messengers, merchants and mercenaries were moving more freely among societies.

This increasing contact facilitated the spread of diseases to biologically naïve populations, the most infamous of these diseases being Yersinia pestis — also known as the Black Death.

Traveling with merchant caravans along trade routes from Asia, the black rat (Rattus rattus) carried disease-bearing fleas to Europe.

The arrival of the bubonic plague in 1346 began a destructive pandemic, and successive waves of disease cut the region's populations by nearly 40% — the highest mortality being in urban areas.

Microbes in the New World

Contacts between previously separated people also resulted in heavy casualties during the age of European exploration and colonization.

For example, the ships of Christopher Columbus, arriving in the Caribbean in 1492, were the first of a wave of vessels that brought Europeans — and the microbes that accompanied them — to the Western Hemisphere.

Killed by disease, not guns

Some of these microorganisms were responsible for eventually wiping out a significant portion of the indigenous peoples.

The military history of the period is filled with tales of miraculous conquests of huge numbers of indigenous peoples by mere handfuls of European troops. But in reality, there were no bonafide miracles.

Most of the damage was inflicted by diseases — particularly smallpox — that for the most part were unwittingly launched by the European invaders.

These new diseases killed approximately two-thirds of the people who encountered them, leaving societies in disarray and unable to muster a decent defense of their territories.

Worldwide trade and disease

In the words of McNeill, "From the Amerindian point of view, stunned acquiescence to Spanish superiority was the only possible response. Native authority structures crumbled: The old gods seemed to have abdicated. The situation was ripe for the mass conversions recorded so proudly by Christian missionaries."

In the more contemporary world, an accelerating movement of people and goods has also been accompanied by growing threats of disease.

Unanticipated global assault

During World War I, influenza traveled from Kansas to Europe along with American troops — and eventually caused more casualties worldwide than did the military hostilities.

And influenza pandemics have regularly spread around the world, sickening hundreds of millions — and killing tens of thousands.

There is now considerable evidence that pathogenic microorganisms are poised to launch new assaults on a global scale.

Many diseases that were thought to have been beaten into submission are making a comeback. And some novel pathogens — to which few people are now immune — are emerging as serious threats to security.

AIDS: A U.S. national security threat

Since 1973, 20 well-known diseases — including tuberculosis, malaria and cholera — have reemerged or spread geographically and at least 30 previously unknown diseases have been identified. Chief among these new diseases is the HIV/AIDS virus.

In an unprecedented move, HIV/AIDS was declared to be a threat to national security by the Clinton administration in April 2000.

Continuing and powerful threats

And, of course, the new threat of biological warfare — and the possible introduction of genetically engineered pathogens — worsens the situation.

In spite of significant advances in medical technology, there are abundant indications that these new and resurgent diseases will be a continuing threat to ecological security.

Infectious diseases are already a leading cause of death, accounting for nearly 30% of the estimated annual fatalities around the world.

Millions are affected

Traditional diseases — such as respiratory infections, especially influenza and pneumonia, as well as diarrhea — currently exact the greatest number of casualties. But HIV/AIDS is rapidly growing in importance.

In 2000, 3.9 million people died from respiratory infections and 2.1 million people died from diarrheal diseases. At the same time, 2.9 million people died from AIDS. Some 42 million people are currently HIV positive. Five million people are newly infected with HIV each year.

TB and Malaria

Tuberculosis (TB) and malaria are the next most significant disease threats to human wellbeing. The World Health Organization declared TB to be a global emergency in 1993.

TB took the lives of 1.7 million people in 2000 and one-third of the world's population is infected with latent TB.

Drug resistance is a growing problem and nearly 50% of those with drug-resistant TB die despite treatment.

Malaria, a tropical disease that was thought to be under control in the 1970s and 1980s, is making a comeback. In 1998, 300 million people were estimated to be infected with malaria — and 1.1 million people died from the disease.

Hepatitis B and C

Most of the deaths occurred in countries of Sub-Saharan Africa, where increases of 7% to 20% annually are expected for the next several years.

Although they have not yet become major killers at this time — accounting for only about 600,000 deaths annually — hepatitis B and C pose a significant future threat.

Ever more vulnerable

Nearly 350 million people are chronic carriers of hepatitis B and some 170 million people are estimated to be infected with hepatitis C.

The nagging question is why — despite numerous technological breakthroughs and repeated claims that the threat of disease would soon be eradicated — does bioinsecurity remain so pervasive?

Both environmental degradation and changes in human behavior are making people more vulnerable to disease organisms.

There are at least seven kinds of environmental and behavioral changes that are now upsetting human-microbe relationship.

They are:

1) Demographic dislocation
2) Technological innovation
3) Increased travel and commerce
4) Microbial adaptation
5) Behavioral changes
6) Persisting poverty
7) Environmental change

Above and beyond

Building biosecurity requires moving beyond the wake-up call represented by HIV/AIDS and emerging bioterrorism — and addressing a series of long-term security issues raised by infectious diseases.

Existing institutions have been shaped and pruned by decades of complacency and budget-cutting in the mistaken belief that the battle against disease has been won.

WHO and its difficulties

The World Health Organization (WHO) was created in 1948 as the UN agency responsible for creating and disseminating international health regulations and guidelines, as well as to provide technical assistance to member countries.

But the WHO has been far from anticipatory or flexible in dealing with the changing disease challenges.

It wasn't until 1995 that a division was created to deal with emerging and contagious diseases. New leadership promises change, but member support will be essential to an effective response.

New strategies

An effective biosecurity policy requires continuing surveillance and rapid response to disease outbreaks. Two surveillance networks have been established in order to monitor and assess disease outbreaks.

The WHO has set up a network called WHONET that links microbiology labs around the world to a central database devoted to detecting reservoirs of drug-resistant microbes and preventing their spread.

Positive trends, but serious problems remain

And a group of scientists in the United States has set up a Program to Monitor Emerging Diseases (ProMED), an electronic mail network that facilitates reporting on — and discussions of — disease outbreaks the world.

While these are positive developments, it is of little use simply to report on disease outbreaks if no response capability exists.

The Centers for Disease Control and Prevention in the United States do send teams of epidemiologists to various countries where disease outbreaks occur. But the agency has had inadequate funding to broaden its role.

Much to be done

While the WHO would in theory be a logical choice to carry out the response function, it now lacks authority, funding, staff and facilities to do so.

Clearly much remains to be done in addressing diseases that can quickly move through all of the neighborhoods of the emerging global city.

Excerpted from Dennis Clark Pirages and Theresa Manley DeGeest’s “Ecological Security: An Evolutionary Perspective on Globalization.” Copyright © 2003 Rowman & Littlefield. Used by permission of the publisher.