Richard Harris

Hospital-acquired infections continue to be a big problem in health care, with 4 percent of patients getting a new infection while hospitalized, a study finds. And 11 percent of those infections turn deadly.

It's the first time that the Centers for Disease Control and Prevention has attempted to catalog all hospital infections, not just the infections with germs on their watch list. Researchers surveyed 183 hospitals nationwide, emphasizing smaller community hospitals.

Using the labor of dozens of undergraduate students, scientists have built a customized yeast chromosome from scratch.

It's a milestone in the rapidly growing field of synthetic biology, where organisms can be tailored for industrial use. In this case, the near-term goal is to understand the genetics of yeast, and eventually the genetics of us.

This was quite an undertaking. Yeast have about 6,000 genes packed in 16 tidy bundles called chromosomes. Each chromosome is an enormous molecule of DNA packed in proteins.

If you want to know what's up with the flu at the moment, you have a few choices: You can get the latest information at Google Flu Trends. Or you can get the official word from the Centers for Disease Control and Prevention, which is based on data that's by now a couple of weeks old.

But a report in the journal Science finds that quicker isn't necessarily better.

The human eye can distinguish more than 2 million distinct colors. But scientists studying smell now say they have their vision colleagues beat: The human nose, they say, can distinguish more than a trillion different smells.

Yes, trillion with a T.

That new figure displaces a much more modest estimate. Until now, smell researchers have been saying the human nose can distinguish about 10,000 smells.

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