Each year, between 5% and 20% of Americans get the flu, and their cases range in severity from mild to life-threatening.

Patients at Rawson-Neal Psychiatric Hospital in Las Vegas have been unable to drink the water or take a shower there since Oct. 2, when the legionella bacterium was detected in the water system.

This has been the worst season ever in Clark County for mosquito-borne West Nile virus, but health authorities say they face a challenge convincing local residents that they need to protect themselves against the tiny bloodsuckers.

In the nearly 50 years since epidemiologists first discovered Legionnaires’ disease, we have learned how to test for it, treat it and prevent it. So why are people still dying from it and why are more and more people becoming sick with it every single year?

There's been a big uptick in cases over the last decade.

Inhaling mist contaminated with Legionella pneumophila can lead to Legionnaires’ disease.

Most cases of infection occur between May and October, when coastal waters are warmest. This could change, however, as summer weather starts earlier and lasts longer.

Like humans, many bacteria like to spend time at the beach. The so-called flesh-eating bacteria, Vibrio vulnificus, don’t just like the beach; they need it, and rely on seasalt for survival. And as with human beachgoers, the warmer the water, the more of them there are.