Because the region is surrounded on three sides by mountain ranges, pollutants get trapped in the valley. Wildfires — such as the blazes that have dirtied the valley’s air this summer — exacerbate asthma symptoms and send more kids to the emergency room.

Nearly 60 years after the first documented case of the AIDS virus, the disease continues to have a disproportionate effect on the Latino community, and particularly gay men.

In California, close to 70,000 patients need regular dialysis, which essentially performs the function of kidneys for patients whose own kidneys are failing. DaVita and Fresenius control 70 percent of the nation’s market. Between them, they reported more than $4 billion in operating profits last year.

Ahead of the federal government, California will begin the open enrollment period for health insurance subsidized by the Affordable Care Act, better known as Obamacare, starting next week.

She knows she’s lucky. At any time, her health could have swung in the other direction. And although the reasons why some people with the disease fare better than others remains a mystery for now, it’s an active area of research — something scientists hope to soon understand better