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In the last ten years, Salmonella infections have affected roughly 7000-12,000 people in the UK every year.
Salmonella is a type of bacteria responsible for the majority of food-related illnesses in the UK; it’s odourless, tasteless, and invisible to the naked eye. Illness linked to Salmonella bacteria is called ‘salmonellosis’, which is commonly referred to as ‘food poisoning’. Although most people that contract salmonellosis can recover without medical attention, sometimes hospitalisation is required.
In this guide, we’ll outline the causes of Salmonella, listing the cooked and uncooked foods than carry these bacteria. Next, we’ll discuss what pets can carry Salmonella and the steps that you can take to avoid contamination.
We’ll then look at the symptoms of Salmonella, how common the infection is, and what groups of people are deemed as ‘high-risk’ for contracting Salmonella food poisoning. Finally, we’ll list some preventative measures that you can take to avoid spreading and contracting Salmonella-related illnesses.
What is Salmonella?
Salmonella is the collective name for a group of bacteria that frequently cause a foodborne illness known as salmonellosis. Every year, an average of 10,000 people in the UK are infected with Salmonella. Although relatively rare, there are occasional multi-country outbreaks of Salmonella that are often linked back to one particular food source. However, in some cases, the root cause of these outbreaks cannot be identified.
The World Health Organisation (WHO) estimates roughly 93.9 million cases of gastroenteritis caused by Salmonella every year. Non-typhoidal salmonellosis (a disease caused by the Salmonella infection) leads to 155,000 fatalities per year worldwide.
There are over 2,300 types of bacteria with the Salmonella genus, with Salmonella Enteritidis and Salmonella Typhimurium responsible for at least 50% of all infections.
In the USA, Salmonella infects around 1.2 million people each year, with 23,000 of these people hospitalised, and approximately 450 fatalities each year.
What causes Salmonella?
Salmonella bacteria are present in the gut of many different farm animals, making the contamination of meat products, eggs, milk, poultry, and some fruits and vegetables reasonably easy. In agricultural environments, fruit and vegetables can come into contact with Salmonella bacteria if they have been stored or harvested near animal manure.
Contamination typically occurs when Salmonella-infected faeces comes into contact with water, crops, or animals. Infection begins when people touch or consume these items and fail to wash their hands.
Animals and humans naturally have small amounts of Salmonella bacteria inside their intestines and stomach. However, intestinal bacteria and stomach acid generally destroy the Salmonella before it invades surrounding cells and replicates. Alternatively, Salmonella can exit the digestive tract before causing any problems.
How do humans contract Salmonella?
People generally contract Salmonella when they eat food that has been contaminated with the bacteria. This could be because the bacteria have come into contact with the food products, raw and cooked foods have been stored together (cross-contamination), or the food handler has failed to adhere to good food hygiene practices.
What foods can cause Salmonella?
There is a wide range of foods that can carry Salmonella bacteria and therefore lead to Salmonella infections in humans. These include:
- Chicken, beef, pork, and turkey
- Fruits and vegetables
- Raw milk, and products made from it
- Raw eggs
- Seafood and raw shellfish
- Raw flour.
Below, we’ll outline each type of food and what measures you can take for Salmonella prevention.
Chicken, beef, pork, and turkey:
Raw and undercooked poultry and meat can cause food poisoning. Both raw meat and poultry may contain traces of Salmonella amongst other harmful bacteria.
- Never wash raw meat or poultry before cooking, even if an old recipe requires this step. When you wash raw meat or poultry, Salmonella bacteria can be spread to utensils, surfaces, and other foods in your kitchen or cooking area.
- All meat and poultry must be cooked thoroughly. Bacteria is killed when meat and poultry are heated to a safe internal temperature. Learn about the recommended cooking temperatures for meats and poultry from the official UK Food Safety website.
- We recommend that you use a cooking thermometer to check food temperatures efficiently. It’s not possible to tell if the meat is cooked thoroughly by inspecting its juices or colour.
- Once cooked, all leftovers must be refrigerated at 40°F or colder within 2 hours of preparation. Significant portions of meat, such as roast joints and whole chickens, should be divided into smaller quantities so that they can cool fast enough to prevent any bacteria from growing.
Fruits and vegetables:
- It’s essential to eat fresh fruit and vegetables as they provide some significant health benefits. However, some raw vegetables and fruits can cause food poisoning if they have come into contact with harmful germs such as Salmonella.
- There are many opportunities for fruit and veg to be contaminated on their journey from farm to table. This includes cross-contamination in the kitchen. The safest way to eat fruit and veg is when they are cooked; the next safest is after they have been washed. Try to avoid eating any fresh, unwashed produce.
Raw milk, and products made from it:
Raw (unpasteurised) milk and any products made from it can make you very sick. This includes soft cheeses such as feta, brie, and camembert, as well as ice cream and yoghurt. Raw milk is known to carry many harmful germs, including Salmonella.
- The most efficient way to make raw milk safe to consume is through the process of pasteurisation. This process heats the milk to a temperature high enough to kill all disease-causing germs.
- Many of the nutritional benefits linked to drinking raw milk are available from pasteurised milk, without putting yourself at risk.
Eggs are one of the leading causes of Salmonella-related food poisoning and can lead to illness, even if the eggs are uncracked and look clean.
- Always purchase pasteurised eggs and egg products when making a recipe that requires undercooked or raw eggs.
- Avoid consuming foods that contain undercooked or raw eggs. This includes eggnog and homemade Caesar salad dressing.
- Try to cook eggs until the whites and yolks are firm.
- Cook all foods that contain eggs thoroughly.
- Never taste raw dough or batter.
- Always keep eggs refrigerated at 40°F or colder.
Seafood and raw shellfish:
Raw shellfish and seafood can carry many different types of harmful bacteria, including Salmonella.
- Seafood should be cooked to 145°F, and leftover seafood must be heated to 165°F.
- To avoid contracting a foodborne infection, never eat fish that is undercooked or raw. This includes certain types of sushi, sashimi, and ceviche.
- Oysters and other filter-feeding shellfish can contain bacteria and viruses that can cause illness or death. Therefore, to avoid contracting food poisoning, cook oysters thoroughly.
To grow, sprouts require warm and humid conditions. Unfortunately, these environments are places where germs can thrive. If you eat lightly cooked or raw sprouts, you run the risk of contracting E.coli, Listeria, or Salmonella.
- Cook sprouts thoroughly to destroy all harmful germs that could be present and minimise your risk of food poisoning.
Typically, raw flour is an agricultural product that isn’t treated to destroy germs. Germs can contaminate grain while it is growing in the field or during the other steps as flour is being produced.
- Bacteria are killed when any food made with flour is cooked. For this reason, you should avoid tasting raw batter or dough.
What pets can carry Salmonella?
Although Salmonella is most frequently contracted when a person consumes contaminated food, bacteria can also be passed between animals and humans. Many animals can carry Salmonella bacteria; these include:
- Reptiles (turtles, lizards, and snakes)
- Amphibians (frogs and toads)
- Poultry (chicks, chickens, ducklings, ducks, geese, and turkeys)
- Other birds (parakeets, parrots, and wild birds)
- Rodents (mice, rats, hamsters, and guinea pigs)
- Other small mammals (hedgehogs)
- Farm animals (goats, calves, cows, sheep, and pigs)
How do animals become infected?
Animals often pick up Salmonella from their environment, from their mothers before they are hatched or born, or from eating contaminated food. Salmonella is naturally present in the intestines of many animals.
When these animals defecate, their stools can contaminate their bodies via scales, feathers, or furs. Also, if these animals live in aquariums, coops, pens, or terrariums, the Salmonella can spread from their faeces across these areas.
Additionally, animals that carry Salmonella often appear clean and healthy. Therefore, you must wash your hands thoroughly after making contact with any animal that can carry Salmonella, especially if you have recently cleaned out their water, food tank, or bedding area.
Pet food products and treats can easily be contaminated with Salmonella and other germs. Also, animals that live in tanks or aquariums can contaminate water with Salmonella; this can lead to illness even if you don’t touch the animal.
What are the symptoms of Salmonella?
Sometimes, Salmonella has no symptoms at all. However, in most cases, the main Salmonella symptoms are:
- Abdominal cramps
- Blood in the stool.
Salmonella’s incubation period can range from several hours up to two days, with most Salmonella infections classified as stomach flu (gastroenteritis).
Salmonella symptoms typically last between two and seven days. That said, diarrhoea can last up to ten days, and it can take a few months for bowel function to return to normal.
Some varieties of Salmonella bacteria can cause typhoid fever. However, this potentially fatal disease is more common among developing countries.
How common is Salmonella?
Salmonella infections are one of the most common forms of food poisoning, with tens of millions of people becoming infected each year globally.
Children are at a higher risk of infection than adults as their immune systems are still developing. Older adults and people that have weak immune systems are also more likely to become infected.
Salmonella infections are more common during the summer months. This is because warm temperatures are ideal for bacterial growth, refrigeration of foods is often delayed, and many people have barbecues, increasing the risk of eating undercooked food and cross-contamination.
Can I get Salmonella from drinking water?
Yes, Salmonella can be contracted from drinking contaminated water. However, this is more common in countries that have inefficient water treatment facilities.
Salmonella can be present in water sources like private wells that are contaminated by faeces from infected animals or humans. There are several ways that waste can enter the water. These include sewage systems, sewage overflows, broken salvage systems, polluted stormwater, and agricultural runoff.
If your household water is sourced from a private well, these areas can be contaminated after flooding, mainly if the well is shallow, has been bored or dug, or has been submerged in floodwater for an extended period.
Who is more likely to become unwell?
Your risk of contracting Salmonella increases if you travel to developing countries or countries with poor sanitation.
In these countries, you must avoid drinking tap water at all costs. Additionally, if you purchase a drink from a cafe, restaurant, or bar, avoid ice. In many cases, the ice is made from tap water, and it may carry Salmonella bacteria.
Also, if you are currently taking medication that weakens the immune system, you should be extra cautious as your risk of contracting Salmonella is higher. As mentioned earlier, children and the elderly are also at a higher risk of picking up Salmonella, as their immune systems tend to be weaker than those of healthy adults.
How do I prevent Salmonella?
There are many ways that you can prevent Salmonella infections, including:
Washing your hands:
- Wash your hands immediately after using the bathroom, handling or eating food, or changing a nappy.
- Make sure that all persons with diarrhoea, especially young children, wash their hands frequently and carefully with warm soapy water to reduce the risk of cross-contamination.
- If you have made contact with pets, farm animals, or animal faeces, always wash your hands immediately.
Clean food preparation areas fully:
- Always separate poultry and raw meat from produce and any other foods when storing or shopping for groceries.
- Thoroughly wash chopping boards, cutlery, utensils, countertops, and hands after handling uncooked poultry and raw meats.
- Wash raw vegetables and fruits before eating.
Avoid unpasteurised foods:
- Avoid unpasteurised milk and foods made from unpasteurised milk.
- Cook and store your food at the appropriate temperatures.
- Never eat raw eggs, and use pasteurised eggs when making any foodstuffs that don’t require cooking.
- Poultry, meat, and hamburgers must be cooked until they are no longer pink in the middle.
- Defrost foods in cold water, the refrigerator, or the microwave. Food must be stored in a fridge that is 40°F or below or a freezer that is 0°F or colder.
Be cautious when swimming:
- Avoid swallowing pool or natural lake water while swimming.
- If you have a diarrhoeal illness, you should avoid swimming in public pools or lakes, bathing with others, or preparing food for others.
We hope you found this guide to Salmonella helpful. Now that you are equipped with the knowledge to prevent Salmonella and recognise the symptoms related to this condition, we wish you the best of luck with practising safe food hygiene practices at all times.