How Quickly Can Bacterial Contamination Occur

Bacterial contamination is one of the most common and dangerous causes of foodborne illness. It happens when harmful bacteria grow on food or transfer from food to humans. How quickly can bacterial contamination occur? The answer depends on many factors, such as the type of food, the temperature, the moisture, and the hygiene practices.

In this blog, we will explain how quickly bacterial contamination occurs in food and humans, and how to prevent it with proper food safety measures.

How Quickly Can Bacterial Contamination Occur

How quickly can bacterial contamination occur in food?

Some foods are more likely to be contaminated by bacteria than others. These include meat, eggs, dairy products, cooked rice, and cut fruits and vegetables. These foods have high water, protein, or starch content that provide ideal conditions for bacteria to multiply.

The temperature is another key factor that affects how quickly bacterial contamination occurs in food. Bacteria grow best in the temperature range of 40–140°F (4–60°C), which is known as the danger zone [1]. In this range, bacteria can double in number in as little as 20 minutes.

To prevent how quickly can bacterial contamination occur on food, it is important to keep hot foods hot (above 140°F or 60°C) and cold foods cold (below 40°F or 4°C) [1]. Food should not be left out at room temperature for more than two hours, or one hour if the temperature is above 90°F (32°C). Food should also be refrigerated or frozen within two hours of cooking or purchasing.

How quickly can bacterial contamination occur in humans?

Bacteria can contaminate humans through different ways, such as:

  • Eating contaminated food that has not been cooked properly or has been cross-contaminated by other foods or utensils.
  • Touching contaminated food or surfaces and then touching the mouth, nose, eyes, or wounds.
  • Drinking contaminated water or beverages that have been made with contaminated water or ice.
  • Sharing utensils, cups, plates, or food with someone who is infected.
  • Being in close contact with someone who is infected and coughs or sneezes.

The time it takes for bacteria to cause illness in humans depends on the type and amount of bacteria ingested, the susceptibility of the person, and the immune system response. Some bacteria can cause illness within a few hours of exposure, while others may take days or weeks to show symptoms.

How to prevent bacterial contamination?

With these simple steps, you can prevent bacterial contamination from happening:

  • Wash hands with soap and water before and after handling food, especially raw meat, poultry, seafood, eggs, and produce.
  • Sanitize equipment, utensils, cutting boards, and countertops before and after using them.
  • Separate raw foods from cooked foods and ready-to-eat foods to avoid cross-contamination. Use different plates and utensils for raw and cooked foods.
  • Cook food to safe internal temperatures using a digital food thermometer. Check the recommended cooking temperatures for different types of foods here [3].
  • Chill food and leftovers within two hours of cooking or purchasing. Refrigerate food at 40°F (4°C) or below and freeze food at 0°F (-18°C) or below [2].
  • Avoid eating raw or undercooked meat, poultry, seafood, eggs, sprouts, unpasteurized milk or juice, or honey.
  • Avoid drinking water from unsafe sources or without proper treatment. Boil water for at least one minute before drinking or using it for cooking. Use bottled water or filtered water if you are unsure about the quality of the water supply.
  • Check the labels and expiration dates of packaged foods and discard any food that is spoiled, moldy, discolored, or has an unpleasant odor.
  • Follow the recalls and alerts issued by the Canadian Food Inspection Agency (CFIA) [4].

How Quickly Can Bacterial Contamination Occur

Bacterial contamination can be prevented by following good food safety practices, but also that more action and collaboration are needed from the government, the industry, and the public to ensure the safety and benefits of food. By following the tips above, you can reduce the risk of how quickly bacterial contamination occurs and protect yourself and others from foodborne illness.

You may have heard of a recent E. coli outbreak at the Calgary daycare [5], where 349 people were infected. Bacterial contamination can cause serious and even fatal consequences, especially for vulnerable groups like children. Hence, it’s important to have proper regulations and better enforcement in place.

At Artron Laboratories, we understand the importance of detecting and preventing bacterial contamination. That’s why we offer rapid diagnostic tests that can detect E. coli O157 and H7 antigens in human fecal samples within 15 minutes. These tests are simple, accurate, and cost-effective, and can help diagnose E. coli infections quickly and prevent further complications. These E. coli O157 and H7 Tests are approved by Health Canada and the FDA and are widely used by health professionals and laboratories.


[1] “Danger Zone” (40 °F – 140 °F) | Food Safety and Inspection Service. (n.d.).
[2] Health Canada. (2021, July 5). Safe food storage.
[3] Health Canada. (2020, May 29). Safe cooking temperatures.
[4] Health Canada. (2022, September 22). Food recalls and alerts.
[5] Toy, A. (2023, September 28). More food regulations not needed in light of Calgary E. coli outbreak: law professors. Global News.

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