How Germs and Viruses Get into Food
Here are some of the ways our food can become contaminated.
- The waste, tissue, intestines and other body parts of even healthy cows, pigs, chickens, turkeys and other animals raised for food have germs, viruses and parasites (bugs) that can cause illness in humans. (See an EPA list of common disease- causing bacteria and viruses harbored by even healthy animals). Animal waste (feces) sometimes gets into the water supply, often through runoff, and is used for irrigation or rinsing of fruits and vegetables. And according to the U.S. Environmental Protection Agency (EPA)1, one dairy farm with 2,500 cows produces as much fecal waste as a city of around 411,000 residents. (See chart comparing human and animal waste production (pdf).)
- Germs from runoff can get into oysters and other filter feeding shellfish.
- A germ that causes a disease called salmonella can infect the ovaries of hens and, in turn, all the eggs the hen produces.
- Fish, cows, and broiler and laying chickens bred in industrial style farms often live in tight, crowded conditions that make it easier for disease to spread.
- To control diseases in large feedlots, farms often use massive amounts of antibiotics (in addition to low dose antibiotics that many farms mix into the animal’s feed to help them put on weight faster). At least half of all antibiotics sold in the U.S. are used in meat production. Scientists fear that the practice could be contributing to the creation of antibiotic-resistant microorganisms. The World Health Organization has stated that antibiotic resistance is one of the top three threats to public health.
- Learn how DHEC is helping farmers get smart about antibiotics on the farm.
1EPA "Risk Management Evaluation for Concentrated Animal Feeding Operations." (pdf) US EPA National Risk Management Laboratory. May 2004: 7.
- Human sewage gets into the water supply, often through runoff from septic tanks that don’t work properly and from sewage system overflows. The contaminated water is used for irrigation or rinsing of fruits and vegetables.
- Bacteria from human sewage runoff and sewage dumped directly into the sea can get into oysters and other filter feeding shellfish, which is why DHEC monitors shellfish beds.
- Meat and poultry body parts and tissues sometimes come into accidental contact with animal guts (intestinals), an example of cross-contamination. With tens of thousands of animals slaughtered daily at some plants, this kind of error can affect many different products.
- Sick or infected humans who handle food can contaminate it with their germs or viruses. (such as the Shigella bacteria, hepatitis A virus and Norwalk virus ).
- Thousands of animals (or body parts from them) may be soaked or cleaned in the same water, so one contaminated animal or part can possibly affect many.
- Germs or viruses from ill or infected humans who handle the food sometimes get into the food.
- Raw animal products sometimes come in contact with other kinds of food, cross-contaminating them.
- Germs and viruses from ill or infected humans who handle the food can get into the food.
- Raw animal foods sometimes come into contact with other kinds of food, cross-contaminating them.
- Overly warm temperatures can cause food to spoil, allowing dangerous germs to multiply.
- When food is not heated to high enough temperatures, germs, viruses and bugs can survive on food.
- Germs can be transferred from a contaminated food to a non-contaminated food if you use the same knife, cutting board or utensil on both foods without washing the surface or items in-between.
- A food that is fully cooked can become re-contaminated if it touches raw meats or other raw foods or drippings that contain germs, viruses or parasites.
- Leaving cooked food unrefrigerated too long can cause germs to grow. Under warm, moist conditions a small number of germs can multiply into millions of germs within 12 hours.
- Two germs that cause illness in humans, Listeria monocytogenes and Yersinia enterocolitica, can actually grow at refrigerator temperatures.
- When people don’t wash their hands carefully before and during food handling, they can pass germs and viruses to food.