And it appears cruise lines are again experiencing a wave of stomach bug outbreaks.
The most likely suspects are noroviruses, a class of rapidly spreading, rapidly mutating viruses.
Although they can occur at any time, they are particularly prevalent in winter and early spring, when people tend to be indoors more.
400 people became ill on a Celebrity Cruise Lines ship during 2 outbreaks in February.
And the Centers for Disease says there have been 8 in all thus far this year, including 4 in one week.
Last year, there were only 15 high-seas outbreaks in all.
Noroviruses also spread quickly in schools, hospitals, nursing homes, and other places where there's a lot of hand-to-hand, or hand-to-surface contact.
Retail health clinics, and individual doctors in the Philadelphia area tell Action News they saw a rise in cases during February, but thus far, no big outbreaks.
In addition to surfaces, the virus can also spread through food and drinks.
It's a very hardy microbe, capable of surviving on surfaces for many hours, and withstanding some bleach cleaning solutions.
So cleanliness is a must - wash your hands often, especially after touching doorknobs, elevator buttons, railings, and other common surfaces. Use alcohol wipes or cleansers, if you can. They are capable of killing more germs.
Don't touch your mouth, eyes, or nose after you've touched those common surfaces.
Try not to use bowls, platters, and dishes used by a number of people.
Remember, the norovirus has an incubation period, AND you may be contagious for up to 3 days after you feel better. So it is very easy to pass it on.
