The Bellingham Herald says health officials believe the first group of norovirus infections started on July 2 with a company function. Then Camp Firwood was temporarily shut down after 23 campers and staff were sickened starting July 18. Health officials will return to the camp this weekend to make sure it is safe to reopen.
Last weekend, several people reported the illness after a chili cookoff on Lummi Island.
None of the groups have reported serious complications, such as dehydration.
Health officials say norovirus spreads easily, especially through food and water at large gatherings. Hand washing can help.