What’s the real risk of infectious gastro-intestinal disease?

Infectious gastrointestinal diseases are quite common, but proper storage, cleaning and cooking of foods and good personal hygiene can lower your risk of illness. According to the U.S. Centers for Disease Control and Prevention (CDC), each year about 76 million Americans become ill from pathogens in food. Salmonella is the second most common cause, accounting for approximately 40,000 reported cases every year, and perhaps 2 to 4 million in all.

Point of entry. The gastrointestinal tract is the point of entry and often the only system affected by foodborne illnesses. Diarrhea, abdominal cramps, vomiting and fever are common to nearly all foodborne infectious diseases. In most cases, the disease plays itself out in a few days, and people may not even be aware of the cause. Occasionally, bacteria, viruses, toxins and parasites are absorbed into the bloodstream and invade other tissues, causing more serious infection that requires medical treatment. Foodborne illness is a larger problem than most people realize for several reasons. For every positive culture (that confirms a cases), there are estimated to be up to 38 actual cases represented by that one culture, explains by epidemic intelligence service officer in the CDC Foodborne and Diarrheal Diseases Branch. Not everyone with diarrhea goes to a doctor, and if they do, the doctor won’t necessarily order a stool culture. If one is taken, it won’t necessarily identify the bacteria involved. If it does identify the bacteria, it won’t necessarily be reported to the health department.

Even with inexact reporting, it’s clear that foodborne infectious diseases are a major public health concern, resulting in 325,000 hospitalizations and 5,200 deaths annually. According to the Economic Research Service of the U.S. Department of Agriculture (USDA), just five foodborne pathogens cost $6.9 billion annually in medical costs and lost productivity. Sadly, that figure only represents the tip of the iceberg; there are more than 250 different foodborne diseases.

Common and serious pathogens. Two of the most common pathogens are Salmonella and Campylobacter jejuni, which live naturally in the intestines of chicken and other poultry. Swine, horses, dogs, cats and reptiles including turtles, lizards and snakes also harbor the bacteria. Campylobacter is especially common in poultry. Surveys from the U.S. Food and Drug Administration Center for Food Safety and Applied Nutrition "Bad Bug Book" have found that between 20 and 100 percent of retail chickens are contaminated. Although common, infection with either Salmonella or Campylobacter is usually not serious. Like many other pathogens, they cause diarrhea, abdominal pain and cramping, fever, and vomiting. Salmonellosis and campylobacterosis generally last a week or less and usually only create serious illness in people with weakened or still-developing immune systems, such as children, the elderly and those with immune diseases like HIV, or who are on chemotherapy.

Another important pathogen is a strain of Escherichia coli (E. coli) known as O157:H57, which is commonly referred to as ‘hamburger E. coli’ because infection with it usually comes from eating contaminated, undercooked beef. Other known sources of infection include contaminated alfalfa sprouts, lettuce, dry-cured salami, unpasteurized fruit juices and milk, and swimming in or drinking water that has been contaminated with sewage. Infection with E. coli is rare but serious: it accounts for an estimated 73,000 cases and 61 deaths each year and can cause severe illness. Another rare but quite serious disease is listeriosis, which is caused by the bacterium Listeria monocytogenes. The symptoms of listeriosis initially may look like many other infectious GI diseases: fever, nausea and diarrhea. But if the infection spreads to the nervous system, symptoms like headache, stiff neck, confusion, loss of balance and convulsions appear.

Listeriosis seriously affects an estimated 2,500 people each year, and of those, about 500 die. It is a particular concern for pregnant women and AIDS patients. Pregnant women are about 20 times more likely to contract the disease than other healthy adults; people with AIDS, nearly 300 times more likely. Other high-risk groups include newborns who may be infected by their mothers; persons with weakened immune systems, cancer, diabetes or kidney disease; the elderly; and people taking glucocorticosteroid medications. Like other foodborne pathogens, Listeria is found in soil and water. It has been found in at least 37 mammal and 17 bird species and may also be in certain fish and shellfish.

People become infected by eating contaminated, uncooked meats and vegetables as well as processed foods that become contaminated after processing, such as soft cheeses and cold cuts from the deli counter. Unpasteurized milk and products made from it may also harbor Listeria.

The viral threat. A common infectious virus received intense public attention last fall when hundred of passengers on several cruise ships operated by different companies contracted Norwalk-like virus. Transmission occurs when infected people don’t wash their hands after using the bathroom and then touch other people, surfaces or food. In some outbreaks, people have contracted Norwalk from eating raw or under-cooked shellfish harvested from waters polluted with sewage. That appears not to be the situation in the recent cruise ship cases. Overall, the exact proportion of GI illness caused by Norwalk-like virus is unknown, but it is widespread. Hepatitis, or inflammation of the liver, is another example of an infectious GI illness that may be transmitted through food but is more commonly spread through other mechanisms. Actually, there are five viruses, including A, B, C, D and E. Hepatitis A and E, like Norwalk-like virus, are spread primarily through fecal-oral contact due to inadequate hygiene or as a results of ingesting water or food that in some ways has been contaminated.

The hepatitis A virus is shed in feces and does not cause chronic illness, explains AGA member, professor of medicine, chief of hepatology and co-director of the liver transplant program at Stanford University Medical Center in Palo Alto, California. Hepatitis A is highly endemic in developing countries. In the United States, the incidence has gradually decreased as our overall hygiene has improved. About 33 percent of Americans have antibodies for hepatitis A, indicating that they have come in contact with the virus. Comparatively, in certain developing countries such as India and China, about 95 percent of the population tests positive for the antibodies. Hepatitis E also is very common in developing countries, but it’s usually only seen in the United States among international travelers. Hepatitis A is most common in young children, where it usually does not cause symptoms. People most at risk are international travelers, homosexual men and those who work in or are cared for in day-care centers and institutions for the developmentally disabled.

A vaccine for hepatitis A exists, but it has not been approved for children under the age of two. The CDC recommends it for international travelers and for people who live in communities where there are prolonged outbreaks.

Risks from seafood. Various viral, bacterial and parasitic infections also can be contracted from seafood, primarily from eating raw or undercooked fish. Examples of these pathogens – all of which are rare in the United States – include vibrio vulnificus, anisakis, marina, vibrio parahaemolyticus and vibrio cholerae. Both fish and shellfish also can absorb environmental contaminants in both fresh and salt water. Although rare, scromboid poisoning is one of the more common seafood-related infectious diseases in the United States. It occurs when certain fish produce a toxin as a result of not being properly cooled after being caught.

The path to contamination. Infectious GI diseases are common, and there’s simply no way to fully safety-proof the food supply. However, you can do many things to reduce your risk. Food isn’t necessarily safe even in developed countries like the United States. First realize that food may be contaminated, as opposed to assuming that it’s clean and pure. Chicken in particular should be treated as if it is contaminated, says AGA member, professor of medicine and director of the Division of Digestive Diseases at the University of Cincinnati. Animal products typically become contaminated during processing when they come in contact with small amounts of intestinal contents. The problem is compounded when the meat from many different animals is combined, for example, in egg preparations and ground beef.

If the contamination level is high enough in one egg or the meat from one animal, you can get a batch effect, where the entire mix becomes contaminated, explains AGA member, chief of gastroenterology at Beth Israel Deaconess Medical Center in Boston and professor of medicine at Harvard Medical School. Other foods, like vegetables and fruits, can be affected when juices form contaminated meat touch them on a countertop for example. Salmonella, in particular, is a potent bug: as few as 15 to 20 bacterial cells may cause infection. As well, certain strains of it are found inside chicken eggs, passed directly from hens.

Reducing risk. One of the best strategies to avoid these types of contamination is to cook meat, poultry and eggs thoroughly. The USDA recommends using a food thermometer to ensure the foods reach an internal temperature of 160 degree Celsius. Just going by the color of meat is not enough because, for example, hamburger meat that has been frozen turns brown more quickly. When served something undercooked while dining out, don’t hesitate to send it back for further cooking, and ask for it to be returned on a clean plate. People who really enjoy rare hamburger might consider grinding their own, that doesn’t eliminate the risk, but it reduces it. If you buy already ground hamburger, it doesn’t matter how much it cost, it’s still coming from a lot of different cows. While undercooked meat and poultry are always discouraged, the same is not true with seafood. The decision to eat sushi, ceviche, oysters on the half shell and other raw products is an individual one, based on understanding the risks and safety factors.

Although it has risks, fish-related foodborne illnesses are more unusual in the United States, so you can’t make a blanket statement to not eat raw fish anytime. Another way to reduce the risk of foodborne illness is to avoid cross-contaminating meats and vegetables. Wash your hands, kitchen work surfaces and utensils with warm soap and water immediately after they’ve been in contact with raw meat or poultry, and keep them separate. Wooden countertops and cutting boards should not be used with poultry and meat because they may harbor organisms even after cleaning. Vegetables should be well-washed and the outer layer of leafy types like lettuce and cabbage removed. Foods must be stored properly. Leftovers must be immediately refrigerated or discarded, as bacteria can grow quickly at room temperature. That makes it especially important to find out about the cooking and storage of foods that you haven’t prepared.

Toxins can multiply quickly in salads and puddings, and the food can taste perfectly normal. So if you’re at a picnic or banquet, you can ask how it was handled, how long it’s been out and whether it was freshly prepared. If you’re uncertain about it, then don’t eat it. Quality control is admittedly easier when cooking at home. When dining out, we’re at the mercy of those who prepare our food and are more likely to get foodborne illnesses in restaurants than at home. One way to lower your risk is to eat at reputable establishments and avoid those known to have problems, for example, through health department citations published in the local newspaper.

Careful selection of suppliers and restaurants is especially important when it comes to seafood. You can’t tell by looking whether fish is safe or not. It doesn’t smell or look bad, because often the infectious agent doesn’t make the seafood itself sick. It’s better to patronize reputable and high-volume markets and restaurants, Those without high volume may store the fish for long periods, and that may lead to infection. Beyond that people at highest risk might consider special precautions such as drinking only pasteurized milk and juices, avoiding unpasteurized soft cheeses like brie and camembert and not eating uncooked hotdogs. Travelers to developing countries, in particular, should take extra care by drinking only bottled water; eating only fruits that can be peeled at the table, such as oranges and bananas; and avoiding raw and undercooked meats and seafoods. Although there will always be some risk, carefully preparing and storing food at home, making informed choices when dining out and practicing good personal hygiene will put you well on the way to lowering your odds of developing an infectious GI disease.