Most people don't realize it, because they're invisible, but microbes make up about a half of the Earth's biomass, whereas all animals only make up about one one-thousandth of all the biomass.

Vaccines and antibiotics have made many infectious diseases a thing of the past; we've come to expect that public health and modern science can conquer all microbes. But nature is a formidable adversary.

Antibiotics are a very serious public health problem for us, and it's getting worse. Resistant microbes outstrip new antibiotics. It's an ongoing problem. It's not like we can fix it, and it's over. We have to fight continued resistance with a continual pipeline of new antibiotics and continue with the perpetual challenge.