Around 90 people fell ill with gastrointestinal symptoms after attending a meeting of women healthcare professionals at the Oregon Zoo last week. The meeting was attended by 220 members of the Women’s Healthcare Associates group last Wednesday morning. After the event, nearly 100 people became sick with what officials believe was Norovirus infection, according to The Oregonian. “Norovirus is the most likely culprit,” Dr. Kristina Hedberg, a state epidemiologist, told the paper. While Norovirus is highly contagious and easily spread via fecal matter, Hedberg says this cluster of illnesses was unusually large. “We tend to see outbreaks this time of year. This one does seem to be larger than many that we see,” Hedberg told The Oregonian. Health officials are currently looking for the source of the virus, which remains unclear. According to Hedberg, the most probable scenario is that an infected food worker contaminated a food that then passed the virus on to other people. The private event was catered by zoo staff. Offerings included typical breakfast fare, such as pastries, muffins, fruit, bagels and cream cheese and spreads, coffee, tea and ice water. Hedberg says the fruit was the most likely source of contamination. Since it was thoroughly washed before serving, it may have been contaminated in the kitchen where it was prepared, she told The Oregonian. The Women’s Healthcare Association says it is working with investigators to determine the source of the virus. “We have taken every precaution to protect the health and well-being of our employees and patients,” said Brian Kelly, CEO of the organization in a statement.