Although Salmonella is generally associated with poultry, it can also contaminate beef. The Centers for Disease Control and Prevention said that 23 percent of outbreaks between 2009 and 2013 were caused by Salmonella.

Scientists have been studying lymph nodes as a "significant source of Salmonella in cattle," Lydia Zuraw reproted for Food Safety News. Some researchers think lymph nodes could cause contaiminated beef, especially ground beef, which has been an issue a couple of times in the last two or three years.

In 2012, 46 people in nine different states were infected with Salmonella Enteritidis. Between late 2012 and early 2013, 22 people in six states became infected with Salmonella Typhimurium, according to Food Safety News.

Generally, lymph nodes are not removed before grinding meat, which means that, if the lymph nodes are contaminated with Salmonella, the ground beef will also be contaminated.

“What we have found is that, in certain times of the year and in certain regions of the country, it’s not uncommon to recover Salmonella from some of the peripheral lymph nodes” Guy Loneragan, a veterinarian epidemiologist and professor of food safety and public health at Texas Tech University, told Food Saftey News.

Loneragan, who is part of a research team that is working on studying Salmonella in cattle lymph nodes, has been presenting the findings to others in the field.

The research is still ongoing.