The number of illnesses in the E. coli outbreak linked to McDonald’s Quarter Pounders has risen to 104, up from 90 at last count, health officials said in an update Wednesday. To date, 34 people have been hospitalized, four have developed serious kidney problems and one has died. The outbreak was announced last month, though some cases date to September, according to the Centers for Disease Control and Prevention. The CDC and McDonald’s have both pointed to slivered onions served on Quarter Pounders as the likely source of the outbreak. McDonald’s said last month that Taylor Farms, a California-based food producer, supplied the onions to affected restaurants. Taylor Farms recalled its yellow onions on Oct. 22. Health officials said Wednesday that there no longer appears to be a food safety concern. In the last week, McDonald’s has resumed selling Quarter Pounders with slivered onions at the affected locations, relying on a different supplier for the onions. Fourteen states have been affected by the outbreak. Colorado has reported the most cases (30), followed by Montana (19) and Nebraska (13). The results of testing on samples of the recalled onions are pending. So far, one sample has come back positive for E. coli, but the strain didn’t match the one in the outbreak, called O157:H7. Most people infected with the E. coli strain recover without treatment. Milder symptoms often include stomach cramps, bloody diarrhea and vomiting. In more severe cases, people can develop high blood pressure, kidney disease, neurological problems or hemolytic uremic syndrome — a condition that can lead to kidney failure. Several lawsuits have been filed against McDonald’s since the outbreak was announced, including a proposed class action. McDonald’s said Wednesday in an online statement that “food safety is something we will never compromise on, and we remain committed to doing the right thing.” This story first appeared on NBCNews.com. More from NBC News: Tufts denies blocking student internships in Democratic congressman’s office Trump names former House Democrat Tulsi Gabbard to be director of national intelligence New York firefighter accused of intentionally setting brush fire on Long Island