Cases of norovirus are on the rise in the United States, especially in the Northeast.

According to recent data from the Centers for Disease Control and Prevention, more than 12% of norovirus tests came back positive last week.

The number is a slight increase from 11.5% from the week before.

The Northeast saw a positive rate that was more than 13%, and has been that high since late January.

The most common symptoms of norovirus are diarrhea, vomiting, nausea and stomach pain, according to the CDC’s website. The health agency says outbreaks can happen anytime, but they occur most often from November to April.

To prevent norovirus, the CDC recommends washing your hands often, rinse fruits and vegetables, cook shellfish thoroughly, stay home when sick and avoid preparing food for others when sick.