"Understanding the recent listeria-linked cheese recall" Listeriosis is almost always acquired by eating contaminated foods. While listeria monocytogenes are quite common in the environment (and at low levels in many fresh foods), the disease itself is rare. There are about 60 reported cases a year in Australia, and that rate is similar to other developed nations, although it's possible that as many cases again go undetected. If detected early enough, infections can be treated successfully with antibiotics. Despite being uncommon, listeriosis is very serious and will be fatal for 20% to 30% of infected people. This statistic is repeated in the current outbreak, which has seen four deaths out of about 20 cases. Listeria monocytogenes is harmless to most people, even when ingested at high levels. Many of us will have the bacteria in our guts at some time and they usually pass through without harming us. People at high risk are those with reduced immune function, such as those on drugs to stop rejection of an organ transplant, or to control an autoimmune disease, such as [lupus](https://theconversation.edu.au/why-its-never-lupus-television-illness-and-the-making-of-a-meme-1198), those receiving anti-cancer treatments, the aged, those with diabetes, liver or kidney disease, and the unborn or very young babies. Indeed, a person with liver cancer is nearly 1000 times more likely to get listeriosis than a healthy young adult, while pregnant women and their foetuses are at about 100 times greater risk. Virtually every person who gets listeriosis has some underlying condition that predisposes them to infection. If people susceptible to listeriosis ingest a large amount of listeria, some may cross from the intestine into the cells of the body, where they can "hide" from the immune system. They then increase in number, moving from cell to cell, and spreading to susceptible sites in the body, where they cause damage to host cells.