Infectious disease in the 21st century
Like most people, you probably got your vaccinations as a child and, since then, you’ve had tetanus boosters, maybe some flu shots, and some antibiotics when you needed them. When you catch a germ, you usually recover quickly. Most people in the United States and other developed countries have good reason to feel smug. They are well protected against infectious disease by vaccination, antibiotics, good hygiene, and general good health.
But for people whose immune systems are weakened by age or disease, it’s a different story. There are plenty of infectious microbes looking for a place to multiply and cause illness and sometimes death. In addition, diseases that just a few years ago seemed to be nearly wiped out often make worrisome comebacks despite widespread vaccination. Resistant strains of infections frequently appear. Still more alarming are the “new and emerging” diseases reported in the news, like SARS or bird flu, for which we have little or no immunity. And sexually transmitted diseases continue to pose a major health threat, with HIV at the top of the list, but also human papillomavirus, herpes simplex, chlamydia, gonorrhea, and syphilis continuing to spread.
What is the status of infectious disease in the 21st century? Wasn’t modern medicine supposed to have this under control by now with vaccines, antibiotics, and antiviral drugs? Are the news reports and alarming headlines about new and emerging diseases to be believed? Will resistant strains of disease overpower our ability to develop new drugs and vaccines? Is the landscape of infectious disease changing in the 21st century, and if so, how can medical science meet the new challenges?
There is no question that, to some degree, the tables have turned. But the tug of war between humans and microbes has always taken place. It is the nature of infectious microbes to damage and kill their hosts. As Cedric Mims described it in Mims’ Pathogenesis of Disease, “If none of the microorganisms associated with man did any damage and none was notably beneficial, they would be interesting but relatively unimportant objects. In fact, they have been responsible for the great pestilences of history, [and] have at times determined the course of history.”
Infectious disease in general and viruses in particular, have, indeed, shaped history. Take, for example, the settlement of North America by Europeans. The smallpox virus and other diseases carried by Europeans played at least as great a role in wiping out the indigenous American populations as did war and weapons. The conquest of Aztecs in Mexico by Hernando Cortes in 1520, for example, was accomplished less by the use of weapons than by the inadvertent introduction of the smallpox virus, endemic in Europe but completely new to the Aztec people, who had no immunity and fell ill and died at a staggering rate. Two years after Cortez arrived, 3.5 million native Americans were dead of smallpox.
The battle of human versus microbe is far from over and is never likely to be so, writes Mims: “Because of their rapid rate of evolution and the constantly changing circumstances of human life, they continue to present threats of future pestilences.”
The age-old story does, however, take some new twists in the 21st century. Several conditions of the modern world combine to influence the threat of infectious disease today.