Street food is nothing new. In ancient Rome and in medieval towns and cities, much of the population had no cooking facilities and relied on food vendors. For today’s traveler, street vendors are not just a source of convenient, tasty and reasonably priced food, but they often provide a sense of adventure, a way to experience local cuisines.

Whether you are visiting New Delhi or New York, some of the best food may come from street vendors. Some food carts are safer than others. In Portland, Ore., often called the food cart/food truck capital of the United States, food-borne illnesses are rare because the city health department inspects mobile restaurants twice a year.

When foods are not cooked, handled or stored properly, they can become contaminated with harmful bacteria, viruses, parasites or toxins. Food-borne illnesses cause severe vomiting, abdominal pain, diarrhea, fever and chills. Symptoms usually occur within 24 to 48 hours and last a short time. Most people recover without medical treatment. Rarely, food-borne illnesses lead to serious complications. Each year, an estimated 48 million people in the United States experience a food-borne illness, resulting in about 3,000 deaths.

Common contaminants include Salmonella, Shigella, E. Coli and Campylobacter bacteria; Giardia and Cryptosporidium parasites; and viruses such as norovirus, rotavirus, cytomegalovirus, herpes simplex and those that cause viral hepatitis.

Raw foods such as meat, poultry, fish and shellfish, eggs, unpasteurized milk and dairy products, and fresh produce often contain harmful bacteria. Bacteria can contaminate food at any time during growth, harvesting or slaughtering, processing, storage and shipping. Foods may also be contaminated during preparation at a restaurant, home, food cart or food truck. If preparers do not thoroughly wash their hands, kitchen utensils, cutting boards or other kitchen surfaces, cross-contamination may spread bacteria to uncontaminated food.

Because bacteria grow quickly at moderate temperatures, cold food should be kept below 40 degrees and hot food above 140 degrees. Refrigeration slows bacterial growth; freezing further slows or stops its spread. However, bacteria become active again when food is brought to room temperature. Thoroughly cooking food kills bacteria.

Parasites can enter the body through food or water and settle in the digestive system. Parasites spread through water contaminated with the feces of infected humans or animals. Foods that come in contact with contaminated water during growth or preparation can become contaminated with parasites. Food preparers who are infected with parasites can contaminate foods if they do not thoroughly wash their hands after using the bathroom and before handling food. In developed countries, parasitic infestations are rare.

Viruses are microorganisms that pass easily from person to person. Because viruses are present in stool or vomit, infected people may contaminate food or drinks if they have not thoroughly washed their hands. Other sources of food-borne viruses include shellfish from contaminated waters and produce irrigated or washed with contaminated water.

When traveling, buy food from busy, clean stalls, carts or trucks. If locals are eating there and the food looks fresh, it’s probably safe. The stands with the longest lines tend to have the freshest and best food. Food vendors should display a current local city license and inspection grade. If you do not see a license, ask for it; if they cannot produce it, eat somewhere else. Thailand’s health department gives out “Clean Food Good Taste” signs to vendors who meet hygiene levels.

Avoid a food cart if you see insects, roaches or mice droppings. Food vendors should be located near a restroom so they can wash their hands frequently. Food workers should have clean hands, wear plastic gloves when preparing or serving food and change gloves often. Food trucks should have a kitchen, a sink and a refrigerator. The vendor should follow safe food practices: keeping food covered, using insulated food carriers, having separate ice for chilling food and serving in drinks, and preventing cross-contamination.

Well-done food is less likely to make you sick. In developing countries, avoid salads and raw vegetables, which might have been washed in contaminated water. Peel fruit yourself, in case the vendor hasn’t washed his or her hands. Tap water and ice cubes aren’t safe in regions where water contamination is a possibility. Drink bottled beverages, and be sure bottled water is sealed; vendors have been known to refill plastic bottles with tap water. Wipe the opening clean and allow it to air dry. Coffee and tea should be steaming hot. Use condiments that are sealed in packages.

Wash your hands with soap and water or hand sanitizer before eating. Even if you are mindful of food safety, you may get a food-related illness. If you do get sick, stay hydrated by drinking safe water. Ask your concierge if your hotel has a doctor on staff who can advise on appropriate treatment. Over-the-counter antidiarrheal medications are not always appropriate. If you have severe abdominal cramps or pain, high fever, blood or mucus in your stool or severe dehydration, get medical care immediately.

The content of this article is for informational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your physician or other qualified health care provider with any questions you may have regarding a medical condition.