Check here for a story on the new strain of norovirus, dubbed the new Sydney norovirus.
UNDATED (CNN) -- The "stomach bug" is spreading again in the U-S.
If someone you know is suffering from severe upset stomach, diarrhea and fatigue, it could be a case of "norovirus." But this illness is a bit tougher than your standard stomach flu.
There have been several major outbreaks on cruise ships in recent years, but we are at the height of a new season... and a new strain.
The norovirus is spread through food or drink that has been contaminated. You can also get it if you touch a contaminated surface or object and them put your hand to your mouth.
Symptoms include abdominal cramps, vomiting, nausea,diarrhea, and fatigue. It hits you suddenly and is described as very explosive.
Dr. Gary Simon of George Washington University Hospital says, "It's very contagious. There are multiple epidemics of it. Other than cleaning the areas, there's not a whole lot people can do about it."
It is so contagious because it is so hard. Typical hand sanitizer alone will not kill it.
Normally, most people infected recover within a few days. In rare cases, it can be fatal, particularly for the very old and very young and those with weaker immune systems.
According to the Centers for Disease Control (CDC), there are more than 20 million cases of the norovirus each year, resulting in about 800 US deaths.
Simon says, "It's so infectious and requires such a low concentration of virus, it's rapidly spread through a population. That's why you see outbreaks on cruise ships, in dormitories, in places where people are in close contact with one another."
The top five ways of protecting yourself according to the CDC include:
-Wash you hand often
-Wash fruits and vegetables
-Cook shellfish thoroughly
-Clean surfaces and wash soiled laundry
-When you are sick, do not prepare food or care for others
With the flu, you can get a flu shot. But there isn't a vaccination right now for the norovirus and no way to treat it. So the best bet is prevention.