Staying well in the 21st century is like playing a game of chess

This article originally appeared in One Health/One Planet, a single-issue magazine that explores how climate change and other environmental shifts are increasing vulnerabilities to infectious diseases by land and by sea. The magazine probes how scientists are making progress with leaders in other fields toward solutions that embrace diverse perspectives and the interconnectedness of all lifeforms and the planet.

On July 30, 1999, the Centers for Disease Control and Prevention published a report comparing data on the control of infectious disease from the beginning of the 20th century to the end. The data showed that deaths from infectious diseases declined markedly. In the early 1900s, pneumonia, tuberculosis and diarrheal diseases were the three leading killers, accounting for one-third of total deaths in the U.S.—with 40 percent being children under five.

Mass vaccinations, the discovery of antibiotics and overall sanitation and hygiene measures eventually eradicated smallpox, beat down polio, cured cholera, nearly rid the world of tuberculosis and extended the U.S. life expectancy by 25 years. By 1997, there was a shift in population health in the U.S. such that cancer, diabetes and heart disease were now the leading causes of death.

The control of infectious diseases is considered to be one of the “10 Great Public Health Achievements.” Yet on the brink of the 21st century, new trouble was already brewing. Hospitals were seeing periodic cases of antibiotic-resistant infections. Novel viruses, or those that previously didn’t afflict humans, began to emerge, causing outbreaks of West Nile, SARS, MERS or swine flu.

In the years that followed, tuberculosis made a comeback, at least in certain parts of the world. What we didn’t take into account was the very concept of evolution: as we built better protections, our enemies eventually boosted their attacking prowess, so soon enough we found ourselves on the defensive once again.