SPRINGFIELD, Mass. (WWLP) - The norovirus, or stomach flu, is on the rise across the country including an increase in Massachusetts cases. The Centers for Disease Control (CDC) has reported wastewater data shows a significant spike in the norovirus in the last few weeks. Baystate Health Medical Director of Infection Control Jacob Smith told 22News he has seen an increase within the network. The norovirus is seen more often in the winter so it is not uncommon to see levels rise. Back in early December, at least 91 outbreaks were reported in one week, more than double compared to the last several years. US flu season is underway, as cases surge in some areas and vaccinations lag What is Norovirus? Norovirus is a highly contagious virus that causes stomach illness. It is commonly spread through contact with infected individuals or contaminated surfaces. Symptoms may include vomiting, diarrhea, stomach cramps, and nausea. Symptoms develop 12 to 48 hours following exposure to the virus. Most people get better within 1 to 3 days. Smith said you can go from feeling fine to pretty ill within just a few hours, and then within a few more days, it goes away for the vast majority of people. Tips to prevent Norovirus Norovirus is a disease that needs the run its course, but there is one big step you can take to prevent getting the illness. Wash hands frequently with soap and water for at least 20 seconds, especially after using the restroom and before eating. (Hand sanitizer is not effective) Clean and disinfect surfaces regularly, especially in high-traffic areas. Avoid close contact with anyone who is ill. Stay home if sick. Children should remain at home if they exhibit symptoms of norovirus, and should only return to school after being symptom-free for at least 24 hours. "Norovirus is an infection that spreads hand to mouth which means often it is on something either on our hands that we are touching or in the food that we are eating, usually bring it to our mouth and that that's how it gets into our body," explained Smith. "So, the way to prevent that is, what your parents or grandparents may have told you, which is wash your hands." Smith said to stay home while you are sick and wash your hands regularly. It is important to note that while hand sanitizer contains alcohol to kill germs, it does not have the ability to kill the norovirus germs. Smith mentioned he is more worried about the increasing cases of the flu around the country. Local News Headlines Coexisting with bears topic of monthly Berkshire Green Drinks event MassMutual Center presents over $5K check to Springfield Boys and Girls Club Springfield Fire Dept. mechanic retires after 38 years Report: Massachusetts ranks low for states people choose to move to WWLP-22News, an NBC affiliate, began broadcasting in March 1953 to provide local news, network, syndicated, and local programming to western Massachusetts. Watch the 22News Digital Edition weekdays at 4 p.m. on WWLP.com.