For the vast majority of people who live in the developed world, infectious disease is an afterthought.

Sure, we still catch colds and (if we're old or immunocompromised) can die of influenza, pneumonia, or food poisoning. Antibiotic resistance is scary -- and directly responsible for about 23,000 deaths in the U.S. each year -- but it hasn't quite become the apocalypse we all feared. In general, the microbial world is just not something the average person has to think about very much.

That luxury of modern life is due to the strong defense provided by the "pillars" of our public health system. According to Dr. Michael Osterholm, these...

Homelessness has surged in some U.S. cities. According to the Wall Street Journal, from 2010 to 2015, homelessness increased 42% in New York City and 12% in Seattle.

A November 2015 report (PDF) by the U.S. Department of Housing and Urban Development (HUD) ranked the top 10 large cities and top 10 small cities by their homeless populations. These counts were conducted on a single night in January.

As shown, the top three large cities (or geographic areas) with the biggest...