Listeria and Cantaloupe: 6 Things You Need to Know

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Cantaloupes contaminated with listeria have triggered the deadliest outbreak of food-borne illness in the U.S. in 10 years, the Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) reported on Tuesday.

So far, 72 people in 18 states have become ill after eating the tainted fruit, reporting fever, muscle aches and diarrhea. Thirteen people have died from the infection, but that number could rise with forthcoming test results by state health departments.

The bacteria has been traced to cantaloupes grown by Jensen Farms in Colorado, and the fruit has been shipped around the country. Here’s some basic information on the bug and how to keep yourself from getting sick.

What is listeria?

Listeria is bacteria from the Listeria monocytogenes family that can cause listeriosis infection. The bacteria have a long incubation period, which means that it may take as long as four weeks for people who have eaten contaminated cantaloupe to feel ill.

Listeriosis typically causes fever and muscle aches, sometimes preceded by diarrhea or other gastrointestinal symptoms. Other symptoms may include headache, stiff neck, confusion, loss of balance and convulsions.

Almost everyone who is diagnosed with listeriosis has “invasive” infection, in which the bacteria spread beyond the gastrointestinal tract, according to the CDC. In some cases, that can lead to more severe illness like meningitis.

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Who is most vulnerable to listeriosis?

In general, people with weakened immune systems, including newborns, pregnant women, the elderly and those with immune disorders, are most likely to become sick if infected. Only rarely do adults with healthy immune systems fall ill.

The bug can cause miscarriage and stillbirth in pregnant women, who are about 20 times more likely than healthy people to develop severe infection. So far, the CDC has not given information about miscarriages or stillbirths associated with the outbreak.

Most of the people have died were over age 60 and at least two were in their 90s.

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Which cantaloupes are affected?

Public health investigators said they found bacterial contamination on melons and on equipment in a packing facility of Jensen Farms in Granada, Colo. The affected cantaloupes are sold under the brand name Rocky Ford, which refers to a region in southeastern Colorado.

Jensen Farms recalled all Rocky Ford cantaloupe shipped between July 29 and Sept. 10, 2011, to at least 17 states (see here for the list of states).

Investigators are still trying to find the original source of contamination. Experts are looking at everything from the water supply and growing and harvesting practices to potential animal intrusions to pinpoint how listeria was introduced to the Jensen Farms fruit.

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Is it safe to eat cantaloupe?

So far, only the fruit from Jensen Farms appears to be contaminated. Fruit from other sources appears to be safe. FDA officials are urging consumers not to eat any cantaloupe from Jensen Farms, and to throw away any melons they may still have bearing the labels “Colorado Grown,” “Distributed by Frontera Produce,” “” or “Sweet Rocky Fords.” However, not all of the recalled cantaloupes are labeled with a sticker, the FDA said.

If you’re in doubt, throw it out or ask your retailer where the fruit came from.

What do I do if I’ve eaten the contaminated cantaloupe?

If you feel ill within two months of eating contaminated cantaloupe, see a physician immediately and make sure to tell your doctor about what you’ve eaten. In high-risk groups, including pregnant women, the bacteria can be fatal. Listeriosis can be treated with antibiotics, however.

Because listeria has such a long incubation period, experts at the CDC and FDA expect that more people will become ill, some seriously so, in the coming weeks.

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How do I avoid getting infected?

Always wash your hands after handling whole melons such as cantaloupe, honeydew and watermelon, and wash or scrub rinds before cutting. Once fruit is cut, eat it promptly or refrigerate the leftovers for no more than a few days.

Unlike some other pathogens, listeria can grow well even in refrigerator temperatures. So federal health officials recommend that anyone who may have contaminated melons throw them out immediately and sanitize thoroughly any surfaces the cantaloupe may have come into contact with.

Alice Park is a writer at TIME. Find her on Twitter at @aliceparkny. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.