Keeping well-hydrated at all times is important, but popular rehydration sachets aren't as helpful as you might think.

Norovirus causes an average of 900 deaths annually mostly among older adults, 109,000 hospitalizations, and 19 million to 21 million cases in the U.S. each year.

The rash typically consists of flat pink or red spots that appear 3 to 5 days after infection. On darker skin, it can be flesh-colored to slightly purplish-gray, with flat to slightly raised bumps.