Some local restaurants are removing green onions from their menus in response to the largest hepatitis A outbreak in U.S. history, which has included three Penn State students.

State College restaurants including Taco Bell, Mad Mex and Panda Express, have stopped using green onions, also called scallions. Health officials announced Friday that green onions were the source of the hepatitis A virus that has infected more than 600 people after an outbreak at a Chi-Chi's restaurant in Monaca's Beaver Valley Mall, outside of Pittsburgh.

Of the 605 people who contracted hepatitis A, at least three of them are students at Penn State's Beaver Campus, said Robert DeWitt, director of student affairs at Beaver Campus. The campus sits only two miles down the road from the restaurant where the outbreak occurred.

Officials at Beaver Campus have been working with both the Pennsylvania Department of Health and University Health Services at University Park to get information out to students about hepatitis A.

Information about the virus has been posted around campus and in residence halls, and e-mail messages were sent to Beaver's 740 students, DeWitt said.

"We've been trying to be as proactive as possible," he said.

Restaurants have also been proactive in dealing with the problem.

Leery customer perception of the garnish and the difficulty of safely preparing scallions prompted Mad Mex restaurants to pull the onions from their ingredients, said Bill Fuller, corporate chef at Big Burrito Restaurant Group, parent company of the six Pennsylvania Mad Mex businesses.

"Better safe than sorry," Fuller said of the green onion elimination, which applies to Mad Mex's State College restaurant, 240 S. Pugh St.

Since Wednesday, Panda Express in the HUB-Robeson Center has also removed scallions from all of its food items, including orange chicken, fried rice and soup. The chain was advised by its corporate headquarters to do so.

"It's not a critical item," said Beaumont Hung, store manager of Panda Express, explaining that the absence of the garnish shouldn't have a profound effect on the restaurant.

Taco Bell, 100 Rolling Ridge Road, was also instructed to stop using green onions.

"Our company stopped sending [green onions] to us and we haven't been using them since," manager Shawna Parrett said.

Three people have died from the outbreak of the illness, which patrons contracted after eating at the Beaver Valley Mall Chi-Chi's between Sept. 14 and Oct. 18. How the green onions first came in contact with the virus still remains unknown.

In response to the Pennsylvania outbreak, the Food and Drug Administration (FDA) has banned Mexican green onion imports.

Chi-Chi's stopped using green onions in all of its restaurants on Nov. 12.

Luke LaBorde, assistant professor of food science at Penn State, said the way green onions are grown and the way they are prepared make them susceptible to disease and likely to pass the disease on to consumers.

"It all comes down to the field sanitation in the place where they grew and packed them," LaBorde said. "They're usually eaten raw, so they don't receive a cooking treatment that could kill the virus."

Following the outbreak, the FDA recommended that green onions be cooked thoroughly and not eaten raw to avoid risk of disease.

Officials have said most people who contracted hepatitis A ate mild salsa, a cheese dip or one of two entrees at the restaurant. The mild salsa, unlike the hot salsa, is made directly at the restaurant.

"Since they serve salsa with just about everything, that's why it got so many people," LaBorde said.

The Associated Press contributed to this report.