Listeria monocytogenes is a bacterium that can cause the disease listeriosis. It is a series disease, especially for pregnant women, people with a weakened immune system, and adults over the age of 65. It causes a variety of symptoms depending on the location the bacterium is affecting. Basic symptoms include fever and diarrhea. However, if the bacteria travels further than the gut, the symptoms depend on if the person is pregnant. If it is a woman who is pregnant, symptoms are usually flu like, however, the infection may lead to miscarriages or life-threatening infections to the newborn. If the people are not pregnant, symptoms can include headaches, stick neck, loss of balance, and convulsions.