Emerging and Re-Emerging Microbes
By the mid-20th century, some scientists thought that medicine had conquered infectious diseases. With the arrival of antibiotics and modern vaccines, as well as improved sanitation and hygiene, many diseases that formerly posed an urgent threat to public health were brought under control or largely eliminated.
The emergence of new microbes and the re-emergence of old microbes has continued, however, as it has throughout history. Several pressures are contributing to the emergence of new diseases such as
- Rapidly changing human demographics
- Rapid global travel
- Changes in land use patterns
- Ecological, environmental, and technological changes
Even public health practices such as widespread antibiotic use are contributing to this emergence. These pressures are both shaping the evolution of microbes and bringing people into closer and more frequent contact with microbes.
Unsanitary conditions in animal agriculture and increasing commerce in exotic animals (for food and as pets) have also contributed to the rise in opportunity for animal microbes to jump from animals to humans. From time to time, with the right combination of selective pressures, a formerly harmless human or animal microbe can evolve into a pathogen that can cause a major outbreak of human disease. At times, changes in societal and environmental factors can also lead to re-emergence of diseases that were previously under control.