A deadly E. coli outbreak in the United States is puzzling health officials who have yet to discover a link between cases to determine a source for the food-borne illness.

According to the Centers for Disease Control and Prevention, 16 cases have been linked to the specific strain of E. Coli, with one person affected in New York, two in Virginia and Washington, five in Oklahoma and six in Arkansas. The alert from the CDC reveals that illnesses began on Dec. 23, 2020, and ranged until Jan. 7, 2021, and more reports of illness are expected. Those affected ranged from 10-95 years old, and 88% of those affected were women.

Nine were also hospitalized, and one death was reported in Washington. Three of those affected also developed hemolytic uremic syndrome, a type of kidney failure, as well. The people who got sick are being interviewed to find out what they ate the week prior to getting sick to determine if there is a link.

According to Arkansas news station KY3, the strain of the illness has been identified as E. Coli O157.

While the number of reported cases makes the outbreak seem small, others may have been sickened as well but didn’t experience severe enough symptoms to have been reported. Previous E. Coli outbreaks have been linked to Caesar Salad kits and Romaine Lettuce.

Symptoms of E. Coli include diarrhea, fever higher than 102 degrees, diarrhea for more than three days that does not improve, bloody diarrhea, excessive vomiting where liquids do not stay down and signs of dehydration.

E.Coli Bacteria as seen under a microscope. Wikimedia Commons/Elapied