Norovirus-like symptoms are turning out to be a stubborn problem as we head into spring. The stomach illness is still spreading in some places, and county health officials are keeping a close eye on places like classrooms, where kids have gotten sick.

Seattle Public Schools sent a letter to families at Sanislo Elementary this week, informing parents that some students and staff are reporting gastrointestinal illnesses.

Public Health Seattle and King County say they have begun a collaborative investigation and response plan.

The district closed John Muir Elementary School for a few days last week after a norovirus outbreak. Crews disinfected the school and kids are back in class this week.

The Snohomish Health District says it thinks at least 10 people experienced norovirus-like symptoms after they visited an indoor trampoline gym in Marysville, called Altitude Trampoline.

The Health District set up a call center for anyone who visited that business and ended up feeling ill: 425-388-5088.

The owner of Altitude Trampoline said they run an exceptionally clean facility and closed for part of the day, Tuesday, for extra cleaning. They have since reopened.

The Health District is monitoring incoming reports to see if any of the cases are part of a larger outbreak.

Here is some information on norovirus symptoms from the Snohomish Health District:

Norovirus is a disease that spreads quickly, often mistakenly called the stomach flu. You can get norovirus from an infected person, contaminated food or water, or by touching contaminated surfaces. The virus causes stomach pain, nausea, diarrhea, and vomiting because your stomach, intestines or both get inflamed (acute gastroenteritis). Symptoms include:

- A sudden onset of illness, usually 24-48 hours after exposure

- Vomiting and nausea

- Diarrhea and stomach cramps

- Headaches, chills, a low-grade fever, muscle aches and tiredness

- Symptoms lasting for 1-2 days

There are no specific drugs or vaccines to treat or prevent norovirus. However, taking the following precautions will help prevent the spread of the virus:

- Wash hands after using the bathroom

- Wash fruits and vegetables thoroughly

- Do not prepare food for others while sick

- Keep children with symptoms home from school or child care, and notify them of the illness

- Clean and disinfect contaminated surfaces with a solution of bleach and water

- Wash all clothes and linens soiled by vomit or fecal matter immediately