Beef that has been undercooked, contaminated with raw meat juice or left out at room temperature for several hours may become tainted with insidious bacteria. Even the strong gastrointestinal juices in your stomach do not kill these bacteria, which will multiply inside the human body at an exponential rate. Although most people's immune systems will rid their bodies of these pathogens with few or no long term effects, the process often causes the unpleasant symptoms of food poisoning.
How soon you develop symptoms depends upon the type of bacteria the beef was infected with. Staphylococcus aureus can cause symptoms as early as an hour after eating. Salmonella can take up to 72 hours. Some bacteria with a long incubation period, such as Listeria monocytogenes, may not produce symptoms for a month. If you discover you have consumed tainted beef, yet do not experience symptoms immediately, do not continue to eat the meat, assuming that the symptoms will not occur. Dispose of it and clean any surfaces that came into contact with it with disinfectant, soap and water.
Most bacteria cause gastrointestinal distress, which varies in intensity with the species consumed and the amount of beef eaten. These symptoms usually begin with nausea, abdominal pain or a headache, which can lead to chills, fever, vomiting and diarrhea. Sometimes Campylobacter jejuni and L. monocytagenes will also cause body aches and swollen lymph glands. In nearly all cases, there is moderate to extreme fatigue. These symptoms are seldom life threatening, except in infants, the elderly and those with a compromised immune system. The most common serious complication is dehydration caused by diarrhea and vomiting.
In the majority of cases, food poisoning caused by contaminated beef resolves itself without medical attention within a week. However some strains of bacteria, such as C. jejuni, can cause symptoms for up to 10 days. The very young, old and immune compromised may experience complications longer than this. Some serious complications of L. monocytogenes, such as meningitis and meningo-encephalitis, can last for weeks.
Tainted beef is not the same as spoiled beef. If your beef is "bad" due to spoilage, other bacteria are at work than those that cause food poisoning. In most cases, they give the meat a bad odor or surface slime, but do not cause noticeable symptoms if eaten. However their presence means the meat is decomposing and should be thrown away. Note that only the bacteria that cause spoilage produce an odor. You cannot judge whether beef is tainted with bacteria that will cause food poisoning by smelling it.