Left unchecked, foodborne parasites and bacteria can be deadly, and controlling them is a matter of serious concern for governments and food producers alike.

A recent outbreak of Escherichia coli, or E. coli, infected 45 people across the United States, mostly in Washington and Oregon, with other cases in Minnesota, California, New York, and Ohio. The Centers for Disease Control and Prevention traced the outbreak to an ingredient used at popular burrito spot Chipotle Mexican Grill. Days later, E. coli was also linked to Costco chicken salad, affecting 19 people.

Chipotle voluntarily closed 43 of its restaurants, before reopening a few weeks later. But officials still don’t know which food ingredient was responsible for the contamination.

You typically can’t see or taste foodborne parasites or bacteria, which is more than a little unsettling. Here are eight that could be lurking in your meal:

When we talk about the E. coli that makes humans sick, we’re usually talking about Shiga toxin-producing E. coli, or STEC. Strains of STEC, most commonly 0157, create a toxin called Shiga that is dangerous for people. It’s generally found in undercooked beef. You can’t see it, taste it, or smell it. But, if you ingest it, you could experience stomach cramps, vomiting, fever, and diarrhea — often bloody.

Unfortunately, there are no medications available to help treat an E. coli infection, and no vaccines that can prevent it. But you can lower your risk by cooking all of your meat thoroughly, until it reaches an internal temperature of 160°F. When preparing beef, keep your work surface clean, frequently wash your hands, and don’t cross-contaminate cooking utensils.

Giardia is considered one of the most common causes of water- and foodborne illness in the United States. It’s usually found in water or food that’s been contaminated with feces from already infected people or animals. When it comes to food, you get it most commonly by eating undercooked pork, lamb, or wild game.

Symptoms of infection, or giardiasis, include cramps, gas, diarrhea, and nausea. It can take as many as one to two weeks for symptoms to appear, and two to six for them to subside. In rare cases, symptoms can last months or even years.

You can prevent giardiasis by washing your hands frequently, drinking water from treated municipal sources, not swallowing water when swimming, and thoroughly cooking your meat.

There are several kinds of tapeworm that can find their way into your body through food. Most of the tapeworms that affect humans come from eating undercooked animal products — particularly pork and beef — as well as raw or undercooked fish that is contaminated. A recent case out of China found a man whose body was “riddled” with tapeworms after consuming large amounts of sushi.

Symptoms can be nonexistent: People can live with a tapeworm growing inside of them and not know for months or even years. When infected, you may experience weight loss, abdominal pain, and irritation of the anus.

You can prevent tapeworm infection by thoroughly cooking all the meat you eat and by washing all fruits and vegetables before you eat or cook with them. An existing infection of pork tapeworm can be made worse by poor hygiene and itching — where eggs are transferred from the anus to the mouth after itching or wiping.

Read more: The man who ‘caught’ cancer from a tapeworm »

There’s a reason why you were taught to always wash your hands after handling animals. Toxoplasma gondii, a microscopic parasite that causes the disease toxoplasmosis, can only reproduce inside of cats, and reach the rest of the world via cat feces. If you touch an infected cat or handle its litter box without washing your hands afterwards, you could easily transmit the parasite to your food when you handle or prepare it. Symptoms are flu-like, and the U.S. Department of Agriculture reports that toxoplasmosis is the third leading cause of death by foodborne illness in the world.

You might also get the parasite from eating undercooked meat or untreated water. The best ways to prevent infection are to thoroughly wash and cook your food, to frequently wash your hands, and to wear gloves when handling cat feces.

Intestinal roundworms, or Ascaris, are generally transmitted when people ingest the eggs of the worm. These eggs can end up in your food when you touch contaminated soil, or eat fruits and vegetables that were grown in such soil without washing them first.

Symptoms are often mild or nonexistent, but may include nausea, vomiting, abdominal pain, as well as coughing and shortness of breath. You can prevent an infection washing your hands frequently, washing all produce before you eat it, and by avoiding any produce you suspect may have been grown with human feces as a fertilizer.

Protected by a hard shell, cryptosporidium, or crypto, is found in fresh produce, milk, and fruit juice. Being infected with the bacteria can cause upset stomach, low fever, cramps, and watery diarrhea. These symptoms usually appear two to 10 days after ingestion.

You can prevent crypto by thoroughly washing all of your produce, drinking pasteurized milk and juices, and by washing your hands frequently throughout the day. If you come in contact with the feces of someone carrying the parasite (when changing a diaper, for instance), you could become infected too.

There are several varieties of flukes or flat worms that may be found in fish, such as Opisthorchiidae and Paragonimus. These flatworms are killed during the cooking process, so your greatest chance of ingesting one is by eating raw fish. Symptoms vary depending on the species, and may take months to show up, but they most often include digestive distress.

While you might be tempted to swear off the sashimi, the chances of infection are fortunately quite low. This is especially true in more pricey, “sushi-grade” seafood. When traveling out of the country, travelers are cautioned against eating raw freshwater fish and dishes where the preparation methods are unknown.

Threadworms, also known as pinworms, include species such as V. vulnificus, shigella, and trichinosi. They are the most common worm infection in the United States, and while they usually only affect children, anyone is at risk for infection. Usually ingested with food due to poor hygiene — a child not washing his hands, for example — pinworms are very easy to spread, meaning that everyone in the household has to be treated if one member is infected.

The worms live for about five to six weeks in the intestines before dying, leaving behind eggs which hatch and take up residence. The most common symptom of a threadworm infection is itching around the anus — a symptom that can lead to greater infestation as children scratch the affected area and transport worms and eggs back up to the mouth and face. Though mostly harmless, threadworms are generally treated with medication and avoided by using improved hygiene practices.