Even just a century ago, infectious diseases (ID) were the leading causes of death worldwide. Since then, public health measures such as sanitation and clean water, along with the development of vaccines, have drastically changed the face of medicine. Chronic diseases — ischemic heart disease and stroke — have mostly replaced infectious diseases as the leading killers worldwide. Low-income countries are the exception, however, and lower-respiratory infections, HIV/AIDS, and diarrheal illnesses still top the list there.
Some notable triumphs in the field of ID include the development of inactivated and live attenuated poliomyelitis vaccines in 1955 and 1962, respectively, and a live attenuated trivalent vaccine against measles, mumps, and rubella in 1971. Antibiotics were introduced with sulfa drugs in 1936, penicillin in 1943, and specific antituberculosis therapy in the 1950s. However, with each of these new successes came subsequent challenges and previously unknown threats. Just after the world celebrated the eradication of smallpox, the first cases of what would become the HIV/AIDS pandemic were reported to the U.S. Centers for Disease Control and Prevention (CDC) in 1981. This was followed by a report in the New England Journal of Medicine of 19 men with a syndrome of opportunistic infections and Kaposi sarcoma. Although the cause of the syndrome was unknown at the time, the author asked, “Were these features manifestations of a primary immunosuppressive viral disease?” In just 35 years, the field of ID has turned this once rapidly fatal disease into one that is chronic and manageable with antiretroviral medications.
Unfortunately, the battle against infectious diseases continues as viruses evolve, bacteria gain antibiotic resistance, and modern travel makes transmission infinitely easier. The field will continue to change and adapt as new epidemics emerge, such as the Ebola virus outbreak in West Africa and the Zika virus outbreak in Brazil.